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At least 253 records · Page 14Linked to original sources
PubMed1990

Effects of spaceflight on the spermatogonial population of rat seminiferous epithelium.

Testes from rats flown on Cosmos 1887 were compared with vivarium control and synchronous control samples. The mean weights of flight testes, normalized for weight per 100 g, were 6.4% less when compared with the vivarium controls. Counts of spermatogonia from tissue sections (seminiferous tubules in maturation stage 6) from five animals in each group revealed 4% fewer spermatogonia in flight testes compared with synchronous controls and 11% fewer spermatogonia in flight samples compared with vivarium controls.

Animals↗
PubMed1992

Comparative study of spermatogonial survival after x-ray exposure, high LET (HZE) irradiation or spaceflight.

Spermatogonial cell loss has been observed in rats flown on Space Lab 3, Cosmos 1887, Cosmos 2044 and in mice following irradiation with X-ray or with high energy (HZE) particle beams. Spermatogonial loss is determined by cell counting in maturation stage 6 seminiferous [correction of seminferous] tubules. With the exception of Iron, laboratory irradiation experiments (with mice) revealed a similar pattern of spermatogonial loss proportional to the radiation dose at levels less than 0.1 Gy. Helium and Argon irradiation resulted in a 5% loss of spermatogonia after only 0.01 Gy exposure. However, significant spermatogonial loss (45%) occured at this radiation level with Iron particle beams. The loss of spermatogonia during each space flight was less than 10% when compared to control (non-flight) animals. This loss, although small, was significant. Although radiation may be a contributing factor in the loss of spermatogonia during space flight, exposure levels, as determined by dosimetry, were not significant to account for the total cell loss observed.

Animals↗
PubMed2000

The U.S.-Russian radiation health effects research program in the Southern Urals.

The Joint Coordinating Committee for Radiation Effects Research (JCCRER) was established through a bilateral U.S.-Russian agreement to support research and exchange information on radiation health effects. The U.S. member agencies include the Department of Energy (DOE), Nuclear Regulatory Commission (NRC), Department of Health and Human Services (DHHS), Department of Defense (DoD), National Aeronautics and Space Administration (NASA), and Environmental Protection Agency (EPA). The Russians are represented by the Ministries of Emergencies (EMERCOM), Atomic Energy (MINATOM) and Health (MINZDRAV), and the Russian Academy of Sciences (IBRAE). The focus of this research is on the workers from the Mayak Production Association (MAYAK) in the Southern Urals and on the neighboring populations along the Techa River exposed to contamination from the plant. The goal of the program is to better define the relationship between the health effects and the chronic low dose and dose-rate exposure, these data being essential to validate current radiation protection standards and practices. The current primary areas of JCCRER research include dose reconstruction, epidemiologic health studies, molecular epidemiology/biodosimetry, and the creation of tissue banks. The organization of the ongoing research conducted under the aegis of the JCCRER and the rationale for this work are described.

Environment↗
PubMed1999

Combined effects of space flight factors and radiation on humans.

The probability that a dose of ionizing radiation kills a cell is about 10,000 times the probability that the cell will be transformed to malignancy. On the other hand, the number of cells killed required to significantly impact health is about 10,000 times the number that must be transformed to cause a late malignancy. If these two risks, cell killing and malignant transformation, are about equal, then the risk that occurs during a mission is more significant than the risk that occurs after a mission. The latent period for acute irradiation effects (cell killing) is about 2-4 weeks; the latent period for malignancy is 10-20 years. If these statements are approximately true, then the impact of cell killing on health in the low-gravity environment of space flight should be examined to establish an estimate of risk. The objective of this study is to synthesize data and conclusions from three areas of space biology and environmental health to arrive at rational risk assessment for radiations received by spacecraft crews: (1) the increased physiological demands of the space flight environment; (2) the effects of the space flight environment on physiological systems; and (3) the effects of radiation on physiological systems. One physiological system has been chosen: the immune response and its components, consisting of myeloid and lymphoid proliferative cell compartments. Best-case and worst-case scenarios are considered. In the worst case, a doubling of immune-function demand, accompanied by a halving of immune capacity, would reduce the endangering dose to a crew member to around 1 Gy.

Animals↗
PubMed1998

Applications of telemedicine in the United States space program.

Since the beginning of human space flight, NASA has been placing humans in extreme and remote environments. There are many challenges in maintaining humans in outer space, including the provision of life-support systems, radiation shielding, and countermeasures for minimizing the effect of microgravity. Because astronauts are selected for their health, among other factors, disease and illness are minimized. However, it is still of great importance to have appropriate medical care systems in place to address illness and injury should they occur. With the exception of the Apollo program, exploration of space has been limited to missions that are within several hundred miles of the surface of the Earth. At the drawn of the 21st century and the new millennium, human exploration will be focused on operation of the International Space Station (ISS) and preparation for human missions to Mars. These missions will present inherent risks to human health, and, therefore, appropriate plans must be established to address these challenges and risks. Crews of long-duration missions must become more independent from ground controllers. New systems, protocols, and procedures are currently being perfected. Application of emerging technologies in information systems and telecommunications will be critical to inflight medical care. Application of these technologies through telemedicine will provide crew members access to information, noninvasive procedures for assessing health status, and guidance through the integration of sensors, holography, decision-support systems, and virtual environments. These technologies will also serve as a basis to enhance training and medical education. The design of medical care for space flight should lead to a redesign of the practice of medicine on Earth.

Computer Communication Networks↗
PubMed2003

Overview of NASA's space radiation research program.

NASA is developing the knowledge required to accurately predict and to efficiently manage radiation risk in space. The strategy employed has three research components: (1) ground-based simulation of space radiation components to develop a science-based understanding of radiation risk; (2) space-based measurements of the radiation environment on planetary surfaces and interplanetary space, as well as use of space platforms to validate predictions; and, (3) implementation of countermeasures to mitigate risk. NASA intends to significantly expand its support of ground-based radiation research in line with completion of the Booster Applications Facility at Brookhaven National Laboratory, expected in summer of 2003. A joint research solicitation with the Department of Energy is under way and other interagency collaborations are being considered. In addition, a Space Radiation Initiative has been submitted by the Administration to Congress that would provide answers to most questions related to the International Space Station within the next 10 years.

Cosmic Radiation↗
PubMed1992

The space life sciences strategy for the 21st century.

In the past, space life sciences has focused on gaining an understanding of physiological tolerance to spaceflight, but, for the last 10 years, the focus has evolved to include issues relevant to extended duration missions. In the 21st century, NASA's long-term strategy for the exploration of the solar system will combine the assurance of human health and performance for long periods in space with investigations aimed at searching for traces of life on other planets and acquiring fundamental scientific knowledge of life processes. Implementation of this strategy will involve a variety of disciplines including radiation health, life support, human factors, space physiology and countermeasures, medical care, environmental health, and exobiology. It will use both ground-based and flight research opportunities such as those found in current on-going programs, on Spacelab and unmanned biosatellite flights, and during Space Station Freedom missions.

Aerospace Medicine↗
PubMed1990

Life sciences issues affecting space exploration.

The U.S. space program is undertaking a serious examination of new initiatives in human space exploration involving permanent colonies on the Moon and an outpost on Mars. Life scientists have major responsibilities to the crew, to assure their health, productivity, and safety throughout the mission and the postflight rehabilitation period; to the mission, to provide a productive working environment; and to the scientific community, to advance knowledge and understanding of human adaptation to the space environment. Critical areas essential to the support of human exploration include protection from the radiation hazards of the space environment, reduced gravity countermeasures, artificial gravity, medical care, life support systems, and behavior, performance, and human factors in an extraterrestrial environment. Developing solutions to these concerns is at the heart of the NASA Life Sciences ground-based and flight research programs. Facilities analogous to planetary outposts are being considered in Antarctica and other remote settings. Closed ecological life support systems will be tested on Earth and Space Station. For short-duration simulations and tests, the Space Shuttle and Spacelab will be used. Space Station Freedom will provide the essential scientific and technological research in areas that require long exposures to reduced gravity conditions. In preparation for Mars missions, research on the Moon will be vital. As the challenges of sustaining humans on space are resolved, advances in fundamental science, medicine and technology will follow.

Adaptation, Physiological↗
PubMedDate not supplied

Radiation transport modeling and assessment to better predict radiation exposure, dose, and toxicological effects to human organs on long duration space flights.

NASA is very interested in improving its ability to monitor and forecast the radiation levels that pose a health risk to space-walking astronauts as they construct the International Space Station and astronauts that will participate in long-term and deep-space missions. Human exploratory missions to the moon and Mars within the next quarter century, will expose crews to transient radiation from solar particle events which include high-energy galactic cosmic rays and high-energy protons. Because the radiation levels in space are high and solar activity is presently unpredictable, adequate shielding is needed to minimize the deleterious health effects of exposure to radiation. Today, numerous models have been developed and used to predict radiation exposure. Such a model is the Space Environment Information Systems (SPENVIS) modeling program, developed by the Belgian Institute for Space Aeronautics. SPENVIS, which has been assessed to be an excellent tool in characterizing the radiation environment for microelectronics and investigating orbital debris, is being evaluated for its usefulness with determining the dose and dose-equivalent for human exposure. Thus far. the calculations for dose-depth relations under varying shielding conditions have been in agreement with calculations done using HZETRN and PDOSE, which are well-known and widely used models for characterizing the environments for human exploratory missions. There is disagreement when assessing the impact of secondary radiation particles since SPENVIS does a crude estimation of the secondary radiation particles when calculating LET versus Flux. SPENVIS was used to model dose-depth relations for the blood-forming organs. Radiation sickness and cancer are life-threatening consequences resulting from radiation exposure. In space. exposure to radiation generally includes all of the critical organs. Biological and toxicological impacts have been included for discussion along with alternative risk mitigation methods--shielding and anti-carcinogens.

Aerospace Medicine↗
PubMed2001

Physical and biological studies with protons and HZE particles in a NASA supported research center in radiation health.

NASA has established and supports a specialized center for research and training (NSCORT) to specifically address the potential deleterious effects of HZE particles on human health. The NSCORT in radiation health is a joint effort between Lawrence Berkeley National Laboratory (LBNL) and Colorado State University (CSU). The overall scope of research encompasses a broad range of subjects from microdosimetric studies to cellular and tissue responses to initial damage produced by highly energetic protons and heavy charged particles of the type found in galactic cosmic rays (GCR) spectrum. The objectives of the microdosimetry studies are to determine the response of Tissue Equivalent Proportional Counter (TEPC) to cosmic rays using ground based accelerators. This includes evaluation of energy loss due to the escape of high-energy delta rays and increased energy deposition due to the enhanced delta ray production in the wall of the detector. In this report major results are presented for 56Fe at 1000, 740, 600 and 400 MeV/nucleon. An assessment of DNA repair and early development of related chromosomal changes is extremely important to our overall understanding of enhanced biological effectiveness of high LET particle radiation. Results are presented with respect to the fidelity of the rejoining of double strand breaks and the implications of misrejoining. The relationship between molecular and cytogenetic measurements is presented by studying damage processing in highly heterochromatic supernumerary (correction of sypernumerary) X chromosomes and the active X-chromosome. One of the important consequences of cell's inability to handle DNA damage can be evaluated through mutation studies. Part of our goal is the assessment of potential radioprotectors to reduce the mutation yield following HZE exposures, and some promising results are presented on one compound. A second goal is the integration of DNA repair and mutation studies. Results are presented on a direct comparison of initial double strand breaks induction, the time course and fidelity of double strand break rejoining, cell killing and mutation induction in the same human model system. In order to understand the carcinogenic potential of protons and HZE particles, the role of damaged microenvironment in this process must be understood. In this project it has been postulated that radiation affects the microenvironment, which then modifies cell interactions in a manner conducive to neoplastic progression. Both TGF-beta and FGF-2 are important components of microenvironment. A recent result on the assessment of the role of FGF-2 and its cross-talk with TGF-beta as a function of radiation quality is presented. Theoretical modeling has so far played a central role in analyzing and integrating experimental data on repair and mutation studies and predicting new phenomena. The integrated NSCORT program also provides a broad training experience for students and postdoctoral fellows in space radiation health.

Animals↗
PubMed2003

[Association between sunburn in children and ultraviolet radiation and ozone layer, during six summers (1996-2001) in Santiago, Chile (33,5 degrees S)].

BACKGROUND: During the recent 10 years the ozone layer has decreased while ultraviolet radiation has increased in Santiago, Chile. AIM: To determine whether the number of sunburns in children correlate with ultraviolet radiation in Santiago. SUBJECTS AND METHODS: During six Austral Summers (1996-2001) children below 15 years old, consulting for sunburn, were evaluated at the "Corporation for the Aid of Burned Children" (COANIQUEM) in Santiago (33.5 degrees S). The number of children with sunburns during each Summer was compared with the corresponding UV-B radiation and the ozone thickness, to establish a probable relation between a geophysical change and its consequences in skin health. The ozone layer values were obtained from the NASA WEB-page and the ultraviolet radiation was measured with a four-channel medium resolution radiometer. RESULTS: In each Summer there was a predominance of sunburns among boys and among ages between 6 and 10 years. During the 96-97 Austral Summer, the highest number of children with sunburns (63) was diagnosed. That Summer also had the highest mean UV-305 nm radiation with an important amount of days with ozone < or = 260 Dobson Units. Only during that Summer an inverse correlation between ozone and UV-305 nm radiation was detected. At the same time the maximal values of Erythemal Dose Rate (33 muWatt cm2), UV Index (13) and Erythemal Daily Dose (7.500 Joule m2) were observed. CONCLUSIONS: In Santiago, Summers with a higher number of days with low ozone protection seem to reappear every 3 years. Understanding the interaction of physical processes that control the ozone layer, may help to design better photo-protection programs for human health.

Adolescent↗
PubMed2001

It takes a tissue to make a tumor: epigenetics, cancer and the microenvironment.

How do normal tissues limit the development of cancer? This review discusses the evidence that normal cells effectively restrict malignant behavior, and that such tissue forces must be subjugated to establish a tumor. The action of ionizing radiation will be specifically discussed regarding the disruption of the microenvironment that promotes the transition from preneoplastic to neoplastic growth. Unlike the highly unpredictable nature of genetic mutations, the response of normal cells to radiation damage follows an epigenetic program similar to wound healing and other damage responses. Our hypothesis is that the persistent disruption of the microenvironment in irradiated tissue compromises its ability to suppress carcinogenesis.

Animals↗
PubMed2001

Influence of the shielding on the space radiation biological effectiveness.

A research program in space radiobiology is described in this report. The program is focused on the effect of the shielding on the biological effects of heavy ions. Both experiments and models are included in the program. Experiments aim to determine genetic effects of heavy ions with or without shielding. Mathematical models, based on Monte Carlo codes, will be used to interpret the biological results. The final goal is to get a feasible model able to predict the radiation-induced biological damage in space, given the free-space radiation field and the space vessel shielding. The grant is supported by the Italian Space Agency (ASI), and involves Italian radiation biophysics groups (Universities of Milan and Naples, National Institute of Health in Rome), in collaboration with NASA (USA), NIRS (Japan), CERN (Switzerland), Brookhaven National Laboratories (USA), and TERA (Italy).

Chromosome Aberrations↗
PubMed1999

A system for low field imaging of laser-polarized noble gas.

We describe a device for performing MRI with laser-polarized noble gas at low magnetic fields (<50 G). The system is robust, portable, inexpensive, and provides gas-phase imaging resolution comparable to that of high field clinical instruments. At 20.6 G, we have imaged laser-polarized (3)He (Larmor frequency of 67 kHz) in both sealed glass cells and excised rat lungs, using approximately 0.1 G/cm gradients to achieve approximately 1 mm(2) resolution. In addition, we measured (3)He T(2)(*) times greater than 100 ms in excised rat lungs, which is roughly 20 times longer than typical values observed at high ( approximately 2 T) fields. We include a discussion of the practical considerations for working at low magnetic fields and conclude with evidence of radiation damping in this system.

Animals↗
PubMed1995

Space and radiation protection: scientific requirements for space research.

Ionizing radiation poses a significant risk to humans living and working in space. The major sources of radiation are solar disturbances and galactic cosmic rays. The components of this radiation are energetic charged particles, protons, as well as fully ionized nuclei of all elements. The biological effects of these particles cannot be extrapolated in a straightforward manner from available data on x-rays and gamma-rays. A radiation protection program that meets the needs of spacefaring nations must have a solid scientific basis, capable not only of predicting biological effects, but also of making reliable estimates of the uncertainty in these predictions. A strategy leading to such predictions is proposed, and scientific requirements arising from this strategy are discussed.

Astronauts↗
PubMed1996

Microprocessor controlled portable TLD system.

An up-to-date microprocessor controlled thermoluminescence dosemeter (TLD) system for environmental and space dose measurements has been developed. The earlier version of the portable TLD system, Pille, was successfully used on Soviet orbital stations as well as on the US Space Shuttle, and for environmental monitoring. The new portable TLD system, Pille'95, consists of a reader and TL bulb dosemeters, and each dosemeter is provided with an EEPROM chip for automatic identification. The glow curve data are digitised and analysed by the program of the reader. The measured data and the identification number appear on the LED display of the reader. Up to several thousand measured data together with the glow curves can be stored on a removable flash memory card. The whole system is supplied either from built-in rechargeable batteries or from the mains of the space station.

Computers↗
PubMed2001

Creation and utilization of a World Wide Web based space radiation effects code: SIREST.

In order for humans and electronics to fully and safely operate in the space environment, codes like HZETRN (High Charge and Energy Transport) must be included in any designer's toolbox for design evaluation with respect to radiation damage. Currently, spacecraft designers do not have easy access to accurate radiation codes like HZETRN to evaluate their design for radiation effects on humans and electronics. Today, the World Wide Web is sophisticated enough to support the entire HZETRN code and all of the associated pre and post processing tools. This package is called SIREST (Space Ionizing Radiation Effects and Shielding Tools). There are many advantages to SIREST. The most important advantage is the instant update capability of the web. Another major advantage is the modularity that the web imposes on the code. Right now, the major disadvantage of SIREST will be its modularity inside the designer's system. This mostly comes from the fact that a consistent interface between the designer and the computer system to evaluate the design is incomplete. This, however, is to be solved in the Intelligent Synthesis Environment (ISE) program currently being funded by NASA.

Algorithms↗