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Biomedical subjects

G Horneck

Publications and source records attributed to G Horneck.

At least 91 records · Page 5Linked to original sources
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↗
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↗
PubMed1974

Viability of Bacillus subtilis spores exposed to space environment in the M-191 experiment system aboard Apollo 16.

During the Apollo 16 space flight, in the experiment system M-191, (microbial response to space environment) spores of Bacillus subtilis 168 were exposed to space vacuum or solar UV irradiation with a peak wavelength of 254 nm or both. The effects of these space factors on the colony-forming ability of the spores were studied. It was found (i) that space vacuum alone did not affect the survival of pre-dried spores; (ii) that space vacuum in combination with solar UV irradiation with a peak wavelength of 254 nm had a synergistic effect, which may by attributed to a UV supersensitivity of the spores during vacuum exposure. These results agreed with findings of simulation experiments on earth. It was concluded that air dried spores may survive exposure to space vacuum if shielded against solar UV irradiation.

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↗
PubMed1973

Solid state AgCl detectors for nuclear tracks with on- and off-response at choice: applications to life sciences.

A new concept of trackforming solid state detectors is presented. These detectors record and accumulate tracks of ionizing particles which can be revealed if they are irradiated with yellow light during the passage of the particle through the detector; otherwise the tracks are dropped by fading. Tracks stabilized by yellow light are stable for months. The detectors consist of thin layers of 200-300 micrometers of Cd-doped AgCl crystals, supported by a thin plate of quartz glass. The invisible latent tracks in these detectors are revealed at microscopically visible size by ultraviolet light. The sensitivity of the crystals against particles of different specific energy transfer depends upon the concentration of Cd; these have rather good thresholds, which permit selective recording in a well-known manner. These AgCl(Cd) crystals have a unique property amongst trackforming detectors; their response can be switched on and off at choice, for instance by electronic triggering of the stabilizing accompanying yellow light. This allows a time assignment of particle tracks, or restriction to tracks of desired particles. Examples of tracks and of applications in cosmic ray research, heavy ion physics, radiobiology and dosimetry are given.

Bacillus subtilis↗
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↗
PubMed1971

Survival of bacterial spores under some simulated lunar surface conditions.

Spores of Bacillus subtilis were exposed to simulated lunar environmental factors, in order to estimate the chance of living matter to survive on the moon. Vacuum, radiation and extreme temperature were selected and their individual and combined influence was tested. High vacuum up to 2 x 10(-7) torr and ultra-high vacuum up to 5 x 10(-9) torr, ultraviolet rays (254 nm) and a temperature of 80 degrees C were used. The results were compared with those of experiments on vegetative cells.

Bacillus subtilis↗
PubMed1970

Survival of microorganisms under simulated space conditions.

Monocellular layers of stationary phase cells of Escherichia coli B/r were exposed to high vacuum of 10(-6) Torr at different temperatures. After simultaneous irradiation with UV of 254 nm or X-rays, the survival was tested as colony forming ability. In vacuum the sensitivity to UV and X-rays was enhanced compared with the controls at atmospheric pressure. Of UV-inactivation in vacuum no photoreactivation was found.

Atmospheric Pressure↗
PubMed1969

Discussion of a possible contamination of space with terrestrial life.

Theoretical considerations were made on what forces and energies affect a particle the size of a microorganism near the Earth and what conditions result for the particle. A transfer of terrestrial life to other celestial bodies seems impossible unless it is done by a spacecraft. This possibility cannot be excluded even after sterilization of the spacecraft on Earth, for in higher layers of the atmosphere the spacecraft could be contaminated again. In this case microorganisms would be subjected to a space flight where decompression is much slower initially than is the case on leaving the Earth's surface with the spacecraft. With these considerations, experiments on microorganisms were carried out in a vacuum chamber. For testing the effect of vacuum on the rate of desorption, mainly of water, measurement was made by a mass spectrometer. In the experiments the decompression rate was varied and different microbiological forms were used, namely, spores and vegetative cells of different cell wall structures. Further experiments in the ultrahigh-vacuum range are necessary and the problems involved are discussed.

Atmospheric Pressure↗
PubMedDate not supplied

Exobiology, the study of the origin, evolution and distribution of life within the context of cosmic evolution: a review.

The primary goal of exobiological research is to reach a better understanding of the processes leading to the origin, evolution and distribution of life on Earth or elsewhere in the universe. In this endeavour, scientists from a wide variety of disciplines are involved, such as astronomy, planetary research, organic chemistry, palaeontology and the various subdisciplines of biology including microbial ecology and molecular biology. Space technology plays an important part by offering the opportunity for exploring our solar system, for collecting extraterrestrial samples, and for utilizing the peculiar environment of space as a tool. Exobiological activities include comparison of the overall pattern of chemical evolution of potential precursors of life, in the interstellar medium, and on the planets and small bodies of our solar system; tracing the history of life on Earth back to its roots; deciphering the environments of the planets in our solar system and of their satellites, throughout their history, with regard to their habitability; searching for other planetary systems in our Galaxy and for signals of extraterrestrial civilizations; testing the impact of space environment on survivability of resistant life forms. This evolutionary approach towards understanding the phenomenon of life in the context of cosmic evolution may eventually contribute to a better understanding of the processes regulating the interactions of life with its environment on Earth.

Astronomical Phenomena↗
PubMedDate not supplied

The biological effectiveness of HZE-particles of cosmic radiation studied in the Apollo 16 and 17 Biostack experiments.

The Biostack experiments I and II were flown on board the Apollo 16 and 17 command modules in order to obtain information on the biological damage produced by the bombardment of heavy high-energy (HZE) particles of cosmic radiation during spaceflight. Such data are required for estimating radiation hazards in manned spaceflight. Seven biological systems in resting state (Bacillus subtilis spores, Colpoda cucullus cysts, Arabidopsis thaliana seeds, and eggs of Artemia salina, Tribolium castaneum and of Carausius morosus) were accommodated in the two Biostacks. By using a special sandwich construction of visual track detectors and layers of biological objects, identification of each hit biological object was achieved and the possible biological damage correlated with the physical features of the responsible HZE-particle. In the different systems the degree of damage depended on whether the hit cell was replaceable or not. A high sensitivity to HZE-particle bombardment was observed on Artemia salina eggs; 90% of the embryos, which were induced to develop from hit eggs, died at different developmental stages. Malformations of the abdomen or the extremities of the nauplius were frequently induced. In contrast, the growth of hit Vicia faba radiculae and the germination of hit Arabidopsis thaliana seeds and hit Bacillus subtilis spores were not influenced remarkably. But there was an increase in multicaulous plants and a reduction in the outgrowth of the bacterial spores. In addition, information was obtained on the fluence of the HZE-particles, on their spectrum of charge and energy loss, and on the absorption by the Apollo spacecraft and the Biostack material itself. This will help to improve knowledge concerning radiation conditions inside of spacecrafts, necessary to secure a maximum possible protection to the astronauts.

Animals↗
PubMedDate not supplied

Critical issues in connection with human planetary missions: protection of and from the environment.

Activities associated with human missions to the Moon or to Mars will interact with the environment in two reciprocal ways: (i) the mission needs to be protected from the natural environmental elements that can be harmful to human health, the equipment or to their operations: (ii) the specific natural environment of the Moon or Mars should be protected so that it retains its value for scientific and other purposes. The following environmental elements need to be considered in order to protect humans and the equipment on the planetary surface: (i) cosmic ionizing radiation, (ii) solar particle events; (iii) solar ultraviolet radiation; (iv) reduced gravity; (v) thin atmosphere; (vi) extremes in temperatures and their fluctuations; (vii) surface dust; (viii) impacts by meteorites and micrometeorites. In order to protect the planetary environment. the requirements for planetary protection as adopted by COSPAR for lander missions need to be revised in view of human presence on the planet. Landers carrying equipment for exobiological investigations require special consideration to reduce contamination by terrestrial microorganisms and organic matter to the Greatest feasible extent. Records of human activities on the planet's surface should be maintained in sufficient detail that future scientific experimenters can determine whether environmental modifications have resulted from explorations. Grant numbers: 14056/99/NL/PA.

Aerospace Medicine↗
PubMedDate not supplied

Biological UV dosimeters in the assessment of the biological hazard from environmental radiation.

To determine the impact of environmental UV radiation, biological dosimeters that weight directly the incident UV components of sunlight have been developed, improved and evaluated in the frame of the BIODOS project. Four DNA-based biological dosimeters ((i) phage T7, (ii) uracil thin layer, (iii) spore dosimeter and (iv) DLR-biofilm) have been assessed from the viewpoint of their biological relevance, spectral response and quantification of their biological effectiveness. The biological dosimeters have been validated by comparing their readings with weighted spectroradiometer data, by comparison with other biological doses, as well as with the determined amounts of DNA UV photoproducts. The data presented here demonstrate that the biological dosimeters are potentially reliable field dosimeters for measuring the integrated biologically effective irradiance for DNA damage.

Bacillus subtilis↗