Biomedical subjects

R Facius

Publications and source records attributed to R Facius.

At least 37 records · Page 2Linked to original sources

PubMed1986

Mutation induction in spores of Bacillus subtilis by accelerated very heavy ions.

Mutation induction (resistance to sodium azide) in spores of Bacillus subtilis was investigated after irradiation with heavy ions from Neon to Uranium with specific particle energies between 0.17 and 18.6 MeV/u. A strong dependence of the mutation induction cross section on particle charge and energy was observed. From the results it was concluded that mutation induction in bacterial spores by very heavy ions is mainly caused by secondary electrons.

Bacillus subtilis↗

PubMed1986

Dosimetric mapping inside BIORACK.

The experiment was flown in different locations inside BIORACK on the D1 mission. It contained different plastic detectors (cellulose nitrate, Lexan, and CR 39) and emulsions to measure the high LET components of the radiation environment. For low LET measurements thermoluminescence dosimeters (LiF) were used. The paper gives data about total dose, charge, energy, and LET spectra so far obtained. These data are compared with data of previous spaceflights.

Cosmic Radiation↗

PubMed1986

Embryogenesis and organogenesis of Carausius morosus under spaceflight conditions.

The influence of cosmic radiation and/or microgravity on insect development was studied during the 7 day German Spacelab Mission D1. Eggs of Carausius morosus of five stages differing in sensitivity to radiation and in capacity to regeneration were allowed to continue their development in the BIORACK 22 degrees C incubator, either at microgravity conditions or on the 1 g reference centrifuge. Using the Biostack concept--eggs in monolayers were sandwiched between visual track detectors--and the 1 g reference centrifuge, we were able to separate radiation effects from microgravity effects and also from combined effects of these two factors in space. After retrieval, hatching rates, growth kinetics and anomaly frequencies were determined in the different test samples. The early stages of development turned out to be highly sensitive to single hits of cosmic ray particles as well as to the temporary exposure to microgravity during their development. In some cases, the combined action of radiation and microgravity even amplified the effects exerted by the single parameters of space. Hits by single HZE particles caused early effects, such as body anomalies, as well as late effects, such as retarded growth after hatching. Microgravity exposure lead to a reduced hatching rate. A synergistic action of HZE particle hits and microgravity was established in the unexpectedly high frequency of anomal larvae. However, it cannot be excluded, that cosmic background radiation or low LET HZE particles are also causally involved in damage observed in the microgravity samples.

Abnormalities, Radiation-Induced↗

PubMed1986

Genetic response of bacterial spores to very heavy ions.

Using spores of two Bacillus subtilis strains differing in repair capacity, we have studied repair and mutation induction in the spores after irradiation with very heavy ions up to uranium with specific particle energies up to 18.6 MeV/u. The results indicate that repair and mutation induction after heavy ion irradiation are closely related to each other and that both phenomena strongly depend on the atomic number and specific energy of the ions. The effects are discussed in comparison with results obtained after X-irradiation.

Bacillus subtilis↗

PubMed1986

Radiation protection problems for the space station and approaches to their mitigation.

With the advent of a permanent manned space station the longstanding problems of radiation protection in manned spaceflight have acquired an immediacy. This paper endeavors to emphasize the gaps of our knowledge which must be closed for effective radiation protection. The information that is required includes the accurate determination of the exposure inside the space station to the various components of tile ionizing radiation, the evaluation of the biological importance of the different radiation qualities and the depth dose distribution of the less penetrating component. There is also the possibility of an interaction with weightlessness. It is necessary to establish adequate radiation protection standards and a system of dosimetric surveillance. There is a need for studies of possible methods of hardening selective shielding of the space station. Spaceflight experiments, which might contribute to the solution of some of these problems are discussed.

Atlantic Ocean↗

PubMed1984

Advanced biostack: experiment 1 ES 027 on Spacelab-1.

The radiobiological properties of the heavy ions of cosmic radiation were investigated on Spacelab 1 by use of biostacks, monolayers of biological test organisms sandwiched between thin foils of different types of nuclear track detectors. Biostacks were exposed to cosmic radiation at several locations with different shielding environments in the module and on the pallet. Evaluations of the physical and biological components of the experiment to date indicate that in general they survived the spaceflight in good condition. Dosimetric data are presented for the different shielding environments.

Animals↗

PubMed1984

Unique radiobiological aspects of high-LET radiation.

Since the beg inning of manned space flight the potentially unique radiobiological properties of the heavy ions of the cosmic radiation had been, apart from possible interactions of radiation effects with biological effects of weightlessness, of major concern with respect to the assessment of radiation hazards in manned space flight. Radiobiological findings obtained from space flight experiments and ground based experiments with densely ionizing radiation are discussed, which suggest qualitative differences between the radiobiological mechanisms of sparsely ionizing and densely ionizing radiation. These findings comprise the observation of a long lateral range of radiobiological effectiveness around tracks of single heavy ions, the observation of micro lesions induced in biological targets by the penetration of heavy ions, the nonadditivity of radiobiological effects from sparsely and densely ionizing radiation, the different kinetics for the expression of late effects induced by sparsely or densely ionizing radiation, and the observation of a reversed dose rate effect for early and late effects induced by densely ionizing radiation. These findings bear on the radiation protection standards to be installed for a general public in manned space flight and on the design of experiments, which intend to contribute to their specification.

Cosmic Radiation↗

PubMed1983

A third order iterative procedure for computing exact confidence limits for Poisson expectation values.

The calculation of exact confidence limits for the expectation value of a Poisson distribution when a single observation of K events is given by means of a second order iterative algorithm was recently presented. Here it is shown that the structure of the equations to be solved admits the use of a third order algorithm, thereby significantly reducing computation time, especially for pocket calculators, with practically no additional computational effort.

Computers↗

PubMed1983

Inactivation probability of heavy ion-irradiated Bacillus subtilis spores as a function of the radial distance to the particle's [correction of paricle's] trajectory.

The understanding of the radiobiological action of heavy ions requires the knowledge of the dependence of the inactivation probability on the distance between the particle's trajectory and the biological test organism (the impact parameter). Spores of Bacillus subtilis with a cytoplasmic core of about 0.22 micrometer cross section are suitable test objects for the study of this radial inactivation probability in its microscopic details. The spores are irradiated at low fluences of some 10(6) ions/cm2 with very heavy ions at different specific energies up to 10 MeV per atomic mass unit u while in fixed contact with visual nuclear track detectors. The methods are described by which the biological response of individual cells can be evaluated and the impact parameter be determined with an accuracy typically better than 0.2 micrometer. The results demonstrate that the common characteristics of inactivation, e.g., an effective range of inactivation extending to at least 3 micrometers, a nonmonotonic dependence of the inactivation probabilities on the radial distance, and the fact that the inactivation probability even for direct central hits on the cytoplasmic core is substantially below one, are nearly independent of the particle energy and type. The results are incompatible with the assumption that the radiobiological effectiveness can be attributed to the dose of secondary electrons as currently understood. They also demonstrate that the widely held notion of an "overkill" at low impact parameters does not apply for the spores even with the most densely ionizing ions.

Argon↗

PubMed1980

Recent radiobiological findings from spaceflight and ground-based studies--an overview.

With respect to radiation standards for manned space flight, we wish to address ourselves to the following topics that we consider pertinent for a realistic assessment of the risk to man when exposed to ionizing radiation under space flight conditions: 1) prediction and measurement of the spectra of the physical traits of cosmic radiation as a function of orbital parameters and the mass shielding of the spacecraft; 2) synergistic or antagonistic modification of radiation effects by dynamic flight conditions and by the space environment; 3) production of biological damage becoming manifest only long after exposure, especially to the heavy ions; and 4) demonstration of possibly specific radiobiological mechanisms for the densely ionizing heavy-ion component of the cosmic radiation. Some recent work referring to these topics will be presented and discussed with emphasis on the high LET component of the cosmic radiation.

Animals↗

PubMed1979

Dosimetric and biological results from the Bacillus subtilis Biostack experiment with the Apollo-Soyuz Test Project.

The evaluation of the Bacillus subtilis experiment has been completed. The biological and the physical results for this part of the Apollo-Soyuz Test Project (ASTP) Biostack experiment are given. This comprises dosimetric data for the cosmic radiation at that orbit as well as biological findings from two types of plastic detectors. Further, the frequency distributions of the physical quantities atomic number, energy and energy loss of the heavy ions within the sample of spores hit are presented. The biological hazard presented by cosmic HZE-particles has been much underestimated.

Bacillus subtilis↗

PubMed1978

Radiobiological results from the Bacillus subtilis Biostack experiments within the Apollo and the ASTP space flights.

In order to check the results of earlier Biostack experiments, new experimental techniques were developed for the Biostack III experiment in the Apollo-Soyuz test project (ASTP). These techniques resulted in an increased accuracy of localization down to 0.2 micrometers for the determination of the impact parameter, accompanied by an increase in the sample size available for biological investigation. In addition, colony forming ability, metabolic mutations, and mutations affecting UV- and x-ray sensitivity were rendered observable by these methods. The biological and physical results obtained so far from the evaluation of the Bacillus subtilis experiment within Biostack III confirm and extend the findings of the previous Biostack experiments. They also add to the questions about the mechanisms of action of the radiation field under investigation, since the observed effects cannot be interpreted in terms of standard concepts.

Bacillus subtilis↗

PubMed1976

Effect of space factors on Escherichia coli B/r cells.

Stationary phase cells of Escherichia coli B/r were inactivated when they were exposed to high vacuum (10(-6) torr). About 5% of the cells were still able to form a colony after 45 min exposure. Vacuum dried cells (0.5 torr, 120 min) show colony forming ability of 30% or more. They were inactivated to about 5% by further vacuum treatment. Vacuum treated cells showed higher permeability for various cell components. UV irradiated E. coli B/r cells in vacuum showed increased UV sensitivity. DNA-protein cross-links were preferentially formed in a vacuum. To obtain 63% of DNA cross linked with protein required 852 erg mm-2 (D37) of UV irradiation in suspension and only 72 erg mm-2 of UV irradiation in vacuum. The protein components of DNA-protein cross-links were hydrolysed with pronase E and the amino acids directly bonding to DNA were determined. The most important amino acids concerned in DNA-protein cross-links seem to be glycine and alanine, followed by aspartic acid (asparagine), glutamic acid (glutamine) and histidine. The sensitivity to X-rays of stationary phase E. coli B/r cells seems to depend on the remaining gas atmospheric in the vacuum since it varies with different pumping systems.

Amino Acids↗

PubMed1976

The Biostack as an approach to high LET research.

By simple geometric and dosimetric arguments the advantage of an experimental approach to high LET radiation research is demonstrated. The Biostack is capable of recording individual hits of heavy ions on single biological targets. This improved method is compared with the common experimental methods for studying biological effects with high LET radiation and is suggested as an methodological improvement in fundamental research.

Cosmic Radiation↗

PubMed1975

Results of the Bacillus subtilis unit of the Biostack II experiment: physical characteristics and biological effects of individual cosmic HZE particles.

The effectiveness of cosmic HZE-particles on unicellular procaryotic, organisms was studied on Bacillus subtilis spores, which were accommodated in the Biostack I and II experiments on board Apollo 16 and 17. Identification of the spores that were hit was achieved by using the Biostack sandwich construction and by precise microscopical measurements of tracks of particles. Germination, outgrowth and the rate of cellular elongation were investigated. A method was developed to determine the charge of each individual HZE particle that penetrated a spore and its energy loss in the region of hit. An attempt was made to establish a connection between these physical characteristics and the biological effects produced.

Bacillus subtilis↗

PubMed1974

Microbial studies in the Biostack experiment of the Apollo 16 mission: germination and outgrowth of single Bacillus subtilis spores hit by cosmic HZE particles.

Bacillus subtilis spores were flown in the Biostack experiment aboard the Apollo 16 command module. The spores embedded in plastic foils were stacked between physical track detectors. The energy loss spectrum of the heavy particles of cosmic radiation was determined. Biological studies were restricted to the high-energy loss component of these particles. Spores that had received single hits whose positions were determined with a typical accuracy of +/- 1 micrometers, were investigated for radiation effects on germination and outgrowth. It was found that germination was not influenced by a hit by an HZE particle, but outgrowth was reduced significantly.

Bacillus subtilis↗

PubMed1973

The Biostack experiment on Apollo 16.

The object of the Biostack experiment is to study the biological effects of high ZE particles of cosmic radiation in order to obtain information on the mechanism of these particles in biological matter. For this purpose individual local evaluation methods have been developed which allow one to identify each biologically effective particle and to correlate the individual hitting particle with the biological effect produced. The Biostack experimental package contains a series of monolayers of selected biological objects (Bacillus subtilis spores, Arabidopsis thaliana seeds, Vicia faba radiculae, Artemia salina eggs) with each layer sandwiched between several different cosmic ion track detectors (nuclear emulsions, cellulose nitrate, polycarbonate). By this arrangement a variety of biological effects due to a single penetrating particle can be analysed. Influence on cellular and tissue development, nuclear damages, and mutation induction are the main investigated effects. These space flight findings will be completed by results of balloon flight and accelerator experiments.

Animals↗

PubMed1972

Effects of simulated space vacuum on bacterial cells.

The effect of vacuum on bacterial cells is related to water desorption. Below water vapour pressure the inactivation remains constant, independent of total pressure and exposure time. In subsequent growth, the lag-phase of the survivors is delayed. Combined treatment with vacuum and radiation (X-rays or uv of 254 nm wavelength) results in synergistic effects, whereas vacuum and heat can act antagonistically. The vacuum inactivated cells (indicated as loss of colony-forming ability) are completely damaged. They do not show cellular elongation, phage production or respiration. The cellular membrane becomes permeable by vacuum exposure: biomolecules are released from the cells when re-suspended after vacuum treatment.

Bacillus subtilis↗