Interplanetary crew exposure estimates for the August 1972 and October 1989 solar particle events

Using the coupled neutron-proton space radiation transport computer code (BRYNTRN), estimates of human exposure in interplanetary space, behind various thicknesses of aluminum shielding, are made for the large solar proton events of August 1972 and October 1989. A comparison of risk assessment in terms of total absorbed dose for each event is made for the skin, ocular lens, and bone marrow. Overall, the doses associated with the August 1972 event were higher than those with the October 1989 event and appear to be more limiting when compared with current guidelines for dose limits for missions in low Earth orbit and more hazardous with regard to potential acute effects on these organs. Both events could be life-threatening if adequate shielding is not provided.     

Analysis of white blood cell counts in mice after gamma- or proton-radiation exposure

In the coming decades human space exploration is expected to move beyond low-Earth orbit. This transition involves increasing mission time and therefore an increased risk of radiation exposure from solar particle event (SPE) radiation. Acute radiation effects after exposure to SPE radiation are of prime importance due to potential mission-threatening consequences. The major objective of this study was to characterize the dose-response relationship for proton and γ radiation delivered at doses up to 2 Gy at high (0.5 Gy/min) and low (0.5 Gy/h) dose rates using white blood cell (WBC) counts as a biological end point. The results demonstrate a dose-dependent decrease in WBC counts in mice exposed to high- and low-dose-rate proton and γ radiation, suggesting that astronauts exposed to SPE-like radiation may experience a significant decrease in circulating leukocytes.     

Response of primary human fibroblasts exposed to solar particle event protons

Solar particle events (SPEs) present a major radiation-related risk for manned exploratory missions in deep space. Within a short period the astronauts may absorb doses that engender acute effects, in addition to the risk of late effects, such as the induction of cancer. Using primary human cells, we studied clonogenic survival and the induction of neoplastic transformation after exposure to a worst case scenario SPE. We simulated such an SPE with monoenergetic protons (50, 100, 1000 MeV) delivered at a dose rate of 1.65 cGy min?1 in a dose range from 0 to 3 Gy. For comparison, we exposed the cells to a high dose rate of 33.3 cGy min?1. X rays (100 kVp, 8 mA, 1.7 mm Al filter) were used as a reference radiation. Overall, we observed a significant sparing effect of the SPE dose rate on cell survival. High-dose-rate protons were also more efficient in induction of transformation in the dose range below 30 cGy. However, as dose accumulated at high dose rate, the transformation levels declined, while at the SPE dose rate, the number of transformants continued to increase up to about 1 Gy. These findings suggest that considering dose-rate effects may be important in evaluating the biological effects of exposure to space radiation. Our analyses of the data based on particle fluence showed that lethality and transforming potential per particle clearly increased with increasing linear energy transfer (LET) and thus with the decreasing energy of protons. Further, we found that the biological response was determined not only by LET but also type of radiation, e.g. particles and photons. This suggests that using γ or X rays may not be ideal for assessing risk associated with SPE exposures.     

Acute biological effects of simulating the whole-body radiation dose distribution from a solar particle event using a porcine model

In a solar particle event (SPE), an unshielded astronaut would receive proton radiation with an energy profile that produces a highly inhomogeneous dose distribution (skin receiving a greater dose than internal organs). The novel concept of using megavoltage electron-beam radiation to more accurately reproduce both the total dose and the dose distribution of SPE protons and make meaningful RBE comparisons between protons and conventional radiation has been described previously. Here, Yucatan minipigs were used to determine the effects of a superficial, SPE-like proton dose distribution using megavoltage electrons. In these experiments, dose-dependent increases in skin pigmentation, ulceration, keratinocyte necrosis and pigment incontinence were observed. Five of 18 animals (one each exposed to 7.5 Gy and 12.5 Gy radiation and three exposed to 25 Gy radiation) developed symptomatic, radiation-associated pneumonopathy approximately 90 days postirradiation. The three animals from the highest dose group showed evidence of mycoplasmal pneumonia along with radiation pneumonitis. Moreover, delayed-type hypersensitivity was found to be altered, suggesting that superficial irradiation of the skin with ionizing radiation might cause immune dysfunction or dysregulation. In conclusion, using total doses, patterns of dose distribution, and dose rates that are compatible with potential astronaut exposure to SPE radiation, animals experienced significant toxicities that were qualitatively different from toxicities previously reported in pigs for homogeneously delivered radiation at similar doses.     

Effect of solar particle event radiation on gastrointestinal tract bacterial translocation and immune activation

Space flight conditions within the protection of Earth's gravitational field have been shown to alter immune responses, which could lead to potentially detrimental pathology. An additional risk of extended space travel outside the Earth's gravitational field is the effect of solar particle event (SPE) radiation exposure on the immune system. Organisms that could lead to infection include endogenous, latent viruses, colonizing pathogenics, and commensals, as well as exogenous microbes present in the spacecraft or other astronauts. In this report, the effect of SPE-like radiation on containment of commensal bacteria and the innate immune response induced by its breakdown was investigated at the radiation energies, doses and dose rates expected during an extravehicular excursion outside the Earth's gravitational field. A transient increase in serum lipopolysaccharide was observed 1 day after irradiation and was accompanied by an increase in acute-phase reactants and circulating proinflammatory cytokines, indicating immune activation. Baseline levels were reestablished by 5 days postirradiation. These findings suggest that astronauts exposed to SPE radiation could have impaired containment of colonizing bacteria and associated immune activation.     

Using electron beam radiation to simulate the dose distribution for whole body solar particle event proton exposure

As a part of the near solar system exploration program, astronauts may receive significant total body proton radiation exposures during a solar particle event (SPE). In the Center for Acute Radiation Research (CARR), symptoms of the acute radiation sickness syndrome induced by conventional radiation are being compared to those induced by SPE-like proton radiation, to determine the relative biological effectiveness (RBE) of SPE protons. In an SPE, the astronaut’s whole body will be exposed to radiation consisting mainly of protons with energies below 50 MeV. In addition to providing for a potentially higher RBE than conventional radiation, the energy distribution for an SPE will produce a relatively inhomogeneous total body dose distribution, with a significantly higher dose delivered to the skin and subcutaneous tissues than to the internal organs. These factors make it difficult to use a ⁶⁰Co standard for RBE comparisons in our experiments. Here, the novel concept of using megavoltage electron beam radiation to more accurately reproduce both the total dose and the dose distribution of SPE protons and make meaningful RBE comparisons between protons and conventional radiation is described. In these studies, Monte Carlo simulation was used to determine the dose distribution of electron beam radiation in small mammals such as mice and ferrets as well as large mammals such as pigs. These studies will help to better define the topography of the time-dose-fractionation versus biological response landscape for astronaut exposure to an SPE.     

The beginning of comparative planetology

The study of the origin of life question is related to the comparative study of the planets in our solar systems and in fact the universe as a whole. Data relevant to the origin of life is being accumulated from the Earth, planets, stars and interstellar space. A variety of spacecraft and Earth based techniques are being used to provide this data.Based on a lecture presented at the special symposium on Photochemistry and the Origin of Life, Bochum, Germany, August 1972.     

Reproduction in Nephrops norvegicus (Decapoda: Nephropidae)

During the period October 1969 to April 1972 a comprehensive study of the reproductive biology of the Norway lobster, Nephrops norvegicus (L. 1758), was made in the Irish Sea. Where possible comparison has been made with data from other areas. The results of the present investigation show that most females are berried annually, egg-laying taking place in August and September, and hatching in April to June of the following year. Moulting and copulation occur in mature females during May to August. In contrast males do not show a marked reproductive cycle, spermatogenesis occurring throughout the year. The method of fertilization is discussed, and it is suggested that this may be internal. Copulatory and egg-hatching behaviour is described, together with details of egg-laying and incubation in the laboratory. A pre-zoeal larval stage is described for the first time, bringing the total number of larval instars to four. The terminology of the larval stages is revised.     

空间环境下肠道菌群失调的研究进展

空间环境中的特殊因素会导致航天员肠道菌群及其代谢产物的失调，对机体会产生系统性的生理影响。本文综述了近年来太空飞行/模拟空间环境对肠道菌群及其代谢产物影响的研究进展。太空飞行/模拟空间环境（space flight/simulated space environment，SF/SPE）可导致侵袭性致病菌的增多及有益菌的减少，肠道炎症加剧与通透性增加，也会引起菌群的有益代谢物减少或有害代谢物增加，进而导致机体内代谢的紊乱，或可诱发其他系统的损伤，从而不利于航天员的健康与工作效率。总结太空飞行/模拟空间环境对肠道菌群产生的影响，可为该领域的后续研究与航天员的在轨健康防护提供科学依据。     

Parasites of the black-tailed jackrabbit in north central Colorado.

Forty-four black-tailed jackrabbits, Lepus californicus melanotis Mearns, 1890, were collected near Denver from August, 1972, through July, 1973, and amined for parasites. Recovered parasites and their infection rates were: Eimeria sp. 100%, Cittotaenia sp.27%, coenuri of Multiceps sp. 57%, Cediopsylla inaequalis 14%, Hoplopsyllus affinis 9%, Haemodipsus setoni 2%, Dermacentor andersoni 14%, and Haemaphysalis leporis-palustris 25%.     

Activation of murine T cells by streptococcal pyrogenic exotoxin type A. Requirement for MHC class II molecules on accessory cells and identification of V beta elements in T cell receptor of toxin-reactive T cells

We investigated the mechanisms of murine T cell activation by streptococcal pyrogenic exotoxin type A (SPE A), focusing on the role of MHC class II molecules on accessory cells (AC) and V beta usage in alpha beta TCR of SPE A-reactive T cells in comparison with staphylococcal enterotoxin B-reactive T cells. L cells transfected with I-Ab genes functioned as effective AC for SPE A-induced responses by C57BL/6 T cells, proliferation, and IL-2 production, but control L cells were not effective AC. Anti-I-Ab mAb inhibited the SPE A-induced responses. Staphylococcal enterotoxin B-induced C57BL/6 T cell blasts were composed of cells bearing V beta 3, members of the V beta 8 family, and V beta 11. Most of the SPE A-induced T cell blasts (about 80%) bore V beta 8.2. mAb reactive to V beta 8.2 markedly inhibited SPE A-induced T cell responses. Apparently, SPE A activates mainly T cells bearing V beta 8.2 in physical association with MHC class II molecules expressed on AC. We also discuss the pathogenic activities of SPE A in relation to toxic shock syndrome.     

Single-parent expression complementation contributes to phenotypic heterosis in maize hybrids

The dominance model of heterosis explains the superior performance of F₁-hybrids via the complementation of deleterious alleles by beneficial alleles in many genes. Genes active in one parent but inactive in the second lead to single-parent expression (SPE) complementation in maize (Zea mays L.) hybrids. In this study, SPE complementation resulted in approximately 700 additionally active genes in different tissues of genetically diverse maize hybrids on average. We established that the number of SPE genes is significantly associated with mid-parent heterosis (MPH) for all surveyed phenotypic traits. In addition, we highlighted that maternally (SPE_B) and paternally (SPE_X) active SPE genes enriched in gene co-expression modules are highly correlated within each SPE type but separated between these two SPE types. While SPE_B-enriched co-expression modules are positively correlated with phenotypic traits, SPE_X-enriched modules displayed a negative correlation. Gene ontology term enrichment analyses indicated that SPE_B patterns are associated with growth and development, whereas SPE_X patterns are enriched in defense and stress response. In summary, these results link the degree of phenotypic MPH to the prevalence of gene expression complementation observed by SPE, supporting the notion that hybrids benefit from SPE complementation via its role in coordinating maize development in fluctuating environments.

The number of single-parent expression complementation patterns is significantly associated with mid-parent heterosis for all surveyed phenotypic traits in maize.     

Stabilization of enzyme activity by incubation in an ethylene atmosphere

Ethylene has a stabilizing effect on the enzymatic activityof yeast alcohol dehydrogenase solutions. The effects of variousconcentrations of ethylene on enzyme activity are demonstrated. (Received August 8, 1972; )     

Feeding and drinking habits of the black rhinoceros in Masai Mara Game Reserve

Feeding and drinking habits of the black rhinoceros (Diceros bicornis L.) population in Masai Mara Game Reserve, Kenya, were studied from May 1971 to August 1972. A total of 108 rhinoceros were recorded in the study area. Feeding rhinoceros were followed behind their feeding tracks until they stopped feeding (or changed to another activity) and the plants which they selected were identified. A technique was used which provided an indication of the relative importance of certain plants in the diet during May to September 1971 (wet-semi-dry), October 1971 to February 1972 (dry) and February to May 1972 (wet-semi-dry). A total of 240 h were spent actually watching feeding rhinoceros in thirteen distribution areas. During this period rhinoceros were observed eating seventy plant species from thirty botanical families. In all distribution areas rhinoceros were very selective for herbs and shrubs, and showed a marked preference for Solanum incanum, Dichrostachys cinerea and Acacia species. Rhinoceros were also observed to visit salt licks which contained sodium, magnesium, potassium and calcium. Two feeding peaks, one in morning and the other in the afternoon were recorded. Black rhinoceros drink water mainly at night. They spend most of the night time near the watering places for they were mostly located in the mornings walking to the feeding grounds.     

Radon and thoron exposures for cave residents in Shanxi and Shaanxi provinces

Measurements of natural radiation were carried out in cave dwellings distributed in the Chinese loess plateau. Those dwellings are located in Shanxi and Shaanxi provinces. Radon and thoron gas concentrations were measured using a passive integrating radon-thoron discriminative detector. Concentrations of thoron decay products were estimated from measurements of their deposition rates. A detector was placed at the center of each dwelling for 6 months and replaced with a fresh one for another 6 months. Measurements were conducted in 202 dwellings from August 2001 through August 2002. A short-term measurement was conducted during the observation period. In addition, gamma-ray dose rates were measured both indoors and outdoors with an electronic pocket dosimeter. Radioactivities in soil were determined by gamma-ray spectrometry with a pure germanium detector. Among 193 dwellings, indoor radon concentrations ranged from 19 to 195 Bq m(-3) with a geometric mean (GM) of 57 Bq m(-3), indoor thoron concentrations ranged from 10 to 865 Bq m(-3) with a GM of 153 Bq m(-3), and indoor equilibrium equivalent thoron concentrations ranged from 0.3 to 4.9 Bq m(-3) with a GM of 1.6 Bq m(-3). Arithmetic means of the gamma-ray dose rates were estimated to be 140 nGy h(-1) indoors and 110 nGy h(-1) outdoors. The present study revealed that the presence of thoron is not negligible for accurate radon measurements and thus that special attention should be paid to thoron and its decay products for dose assessment in such an environment. More systematic studies are necessary for a better understanding of thoron and its decay products.     

Seasonal locust development potential in the Niger area analyzed through ecoclimatological interpretation of satellite images

Images of satellite ERTS (LANDSAT)-1 taken during 1972/73 have been used for ecoclimatological mapping of optimum breeding habitats of the African migratory losusts (Locusta migratoria migratorioides R. & F.) in the middle Niger area. The seasonal shifting of the optimum area for locust (hopper) development both in space and time has been characterized by thermal (mean air temperatures of the months between 25 and about 33°C) and hydric (soil moisture for plants available, but below field capacity) criteria. Examples of the interpretation of favorable (very humid), tolerable (humid) and intolerable, (either flooded or very dry soil or soil without vegetation cover) conditions for development are given. The possibilities are discussed to forecast the chances of hopper development.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

Application of the C3-Binding Motif of Streptococcal Pyrogenic Exotoxin B to Protect Mice from Invasive Group A Streptococcal Infection

Group A streptococcus (GAS) is an important human pathogen that produces several extracellular exotoxins to facilitate invasion and infection. Streptococcal pyrogenic exotoxin B (SPE B) has been demonstrated to be an important virulence factor of GAS. Our previous studies indicate that SPE B cleaves complement 3 (C3) and inhibits the activation of complement pathways. In this study, we constructed and expressed recombinant fragments of SPE B to examine the C3-binding site of SPE B. Using enzyme-linked immunosorbent assays and pull-down assays, we found that the C-terminal domain, containing amino-acid residues 345–398, of SPE B was the major binding site of human serum C3. We further identified a major, Ala³⁷⁶-Pro³⁹⁸, and a minor C3-binding motif, Gly³⁴⁶-Gly³⁶⁰, that both mediated the binding of C3 complement. Immunization with the C3-binding motifs protected mice against challenge with a lethal dose of non-invasive M49 strain GAS but not invasive M1 strains. To achieve higher efficiency against invasive M1 GAS infection, a combination of synthetic peptides derived from C-terminal epitope of streptolysin S (SLSpp) and from the major C3-binding motif of SPE B (PP6, Ala³⁷⁶-Pro³⁹⁸) was used to elicit specific immune response to those two important streptococcal exotoxins. Death rates and the severity of skin lesions decreased significantly in PP6/SLSpp-immunized mice that were infected with invasive M1 strains of GAS. These results indicate a combination of the C3-binding motif of SPE B and the protective epitope of SLS could be used as a subunit vaccine against invasive M1 strains group A streptococcal infection.     

Effects of 28Si Ions, 56Fe Ions,and Protons on the Induction of Murine Acute Myeloid Leukemia and Hepatocellular Carcinoma

Estimates of cancer risks posed to space-flight crews by exposure to high atomic number, high-energy (HZE) ions are subject to considerable uncertainty because epidemiological data do not exist for human populations exposed to similar radiation qualities. We assessed the carcinogenic effects of 300 MeV/n ²⁸Si or 600 MeV/n ⁵⁶Fe ions in a mouse model for radiation-induced acute myeloid leukemia and hepatocellular carcinoma. C3H/HeNCrl mice were irradiated with 0.1, 0.2, 0.4, or 1 Gy of 300 MeV/n ²⁸Si ions, 600 MeV/n ⁵⁶Fe ions or 1 or 2 Gy of protons simulating the 1972 solar particle event (1972SPE) at the NASA Space Radiation Laboratory. Additional mice were irradiated with ¹³⁷Cs gamma rays at doses of 1, 2, or 3 Gy. All groups were followed until they were moribund or reached 800 days of age. We found that ²⁸Si or ⁵⁶Fe ions do not appear to be substantially more effective than gamma rays for the induction of acute myeloid leukemia. However, ²⁸Si or ⁵⁶Fe ion irradiated mice had a much higher incidence of hepatocellular carcinoma than gamma ray irradiated or proton irradiated mice. These data demonstrate a clear difference in the effects of these HZE ions on the induction of leukemia compared to solid tumors, suggesting potentially different mechanisms of tumorigenesis. Also seen in this study was an increase in metastatic hepatocellular carcinoma in the ²⁸Si and ⁵⁶Fe ion irradiated mice compared with those exposed to gamma rays or 1972SPE protons, a finding with important implications for setting radiation exposure limits for space-flight crew members.     

micF RNA is a substrate for RNase E

Abstract The speA gene encoding streptococcal erythrogenic toxin A (SPE A) from Streptococcus pyogenes bacteriophage T12 was overexpressed in Escherichia coli under the control of the T7 promoter. Since most of the expressed protein was found in the periplasmic space, an osmotic shock extraction with 0.5 M sucrose resulted in a highly enriched preparation of SPE A. An additional two-step purification employing high pressure liquid chromatography resulted in a purified SPE A protein.     

Measurements of secondary neutrons from cosmic radiation with a Bonner sphere spectrometer at 79°N

Air crew members and airline passengers are continuously exposed to cosmic radiation during their flights. Particles ejected by the sun during so-called solar particle events (SPEs) in periods of high solar activity can contribute to this exposure. In rare cases the dose from a single SPE might even exceed the annual dose limit of 1 mSv above which dose monitoring of air crews is legally required in Germany. Measurements performed by means of neutron monitors have already shown that the relative intensity of secondary neutrons from cosmic radiation is enhanced during an SPE, particularly at regions close to the magnetic poles of the Earth where shielding of the cosmic radiation by the geomagnetic field is low. Here we describe a Bonner sphere spectrometer installed at the Koldewey station at 79°N, i.e. about 1,000 km from the geographic North pole, which is designed to provide first experimental data on the time-dependent energy spectrum of neutrons produced in the atmosphere during an SPE. This will be important to calculate doses from these neutrons to air crew members. The system is described in detail and first results are shown that were obtained during quiet periods of sun activity.