Early and late damages induced by heavy charged particle irradiation in embryonic tissue of Arabidopsis seeds.

Early and late effects of accelerated heavy ions (HZE) on the embryonic tissue of Arabidopsis thaliana seeds were investigated seeing that initial cells of the plant eumeristems resemble the original cells of animal and human tissues with continuous cell proliferation. The endpoints measured were lethality and tumorization in the M1-generation for early effects and embryonic lethality in the M2-generation for late effects. The biological endpoints are plotted as functions of the physical parameters of the irradiation i.e. ion fluence (p/cm2), dose (Gray), charge Z and linear energy transfer (LET). The results presented contribute to the estimation of the principles of biological HZE effects and thus may help to develop a unified theory which could explain the whole sequence from physical and chemical reactions to biological responses connected with heavy ion radiation. Additionally, the data of this paper may be used for the discussion of the quality factor for heavy ion irradiation needed for space missions and for HZE-application in radio-therapy by use of accelerators (UNILAC, (SIS/ESR), BEVALAC).     

Mammalian cell cultivation in space.

Equipment used in space for the cultivation of mammalian cells does not meet the usual standard of earth bound bioreactors. Thus, the development of a space worthy bioreactor is mandatory for two reasons: First, to investigate the effect on single cells of the space environment in general and microgravity conditions in particular, and second, to provide researchers on long term missions and the Space Station with cell material. However, expertise for this venture is not at hand. A small and simple device for animal cell culture experiments aboard Spacelab (Dynamic Cell Culture System; DCCS) was developed. It provides 2 cell culture chambers, one is operated as a batch system, the other one as a perfusion system. The cell chambers have a volume of 200 microliters. Medium exchange is achieved with an automatic osmotic pump. The system is neither mechanically stirred nor equipped with sensors. Oxygen for cell growth is provided by a gas chamber that is adjacent to the cell chambers. The oxygen gradient produced by the growing cells serves to maintain the oxygen influx by diffusion. Hamster kidney cells growing on microcarriers were used to test the biological performance of the DCCS. On ground tests suggest that this system is feasible.     

DNA-lesion and cell death by alpha-particles and nitrogen ions.

When the natural logarithm of the surviving fraction is plotted against the dose of radiation, curves with shoulders at relatively high survival levels are obtained after gamma-rays. The curves were practically linear in case of HMV-I and HA-1 cells irradiated by charged particle beams. These cells were derived from human malignant melanoma and Chinese hamster cells, respectively. The amount of DNA single strand breaks (ssb) by gamma-rays or nitrogen-ions (LET=530KeV/micrometers) in HMV-I cells increases linearly with increment in dose, when the ssb is detected using the alkaline elution technique. There is no close relationship between the dose-response curve of the ssb and the dose-survival curves after gamma-rays or N-ions. The amount of DNA double strand breaks (dsb) by gamma-rays increases quadratically with increment of dose, in both HMV-I cells and HA-1 cells, when the dsb is detected using the neutral elution technique. The survival fraction for HA-1 cells is slightly higher than that for HMV-I cells, at the same dose, and the amount of dsb for HA-1 cells is considerably greater than that for HMV-I cells. These results suggest that the radiosensitivities to gamma-rays in different cell lines do not correspond to the number of DNA strand breaks. The amount of both non-repairable ssb and dsb also increases quadratically with increment of dose for gamma-rays and almost linearly with increment of dose for N-ions and alpha-particles (LET=36keV/micrometers for HA-1 cells and LET=77keV/micrometers for HMV-I cells). The dose-response curves for non-repairable dsb in case of these radiations seemed to mirror image the dose-survival curves for these radiations, in both cell lines. The number of non-repairable DNA strand breaks in the two cell lines, at the same level of survival was much the same. These results show the close relationship between the induction of non-repairable DNA strand breaks and cell killing.     

Neoplastic transformation of mouse C3H 10T1/2 and Syrian hamster embryo cells by heavy ions.

C3H 10T1/2 mouse-embryo fibroblasts were used for transformation experiments to study the effectiveness of various heavy ions with energies up to 20 MeV/u and LET values from 170 to 16,000 keV/micrometers. The transformation frequency per unit absorbed dose decreased with increasing ionization density; at the highest values of LET we found a decrease even of the transformation efficiency per unit fluence. Uranium ions at energies of 5, 9, and 16.3 MeV/u did not induce any transformation. In additional studies primary Syrian hamster embryo cells (SHE) were exposed to heavy ions in order to characterize cytological and molecular changes which may be correlated with neoplastic transformation. Growth behaviour, chromosomal status, tumorigenicity in nude mice, and expression of oncogenes of transformed cell lines were examined     

Integrated CIS VLF/Omega receiver design

The design of an integrated Russian-VLF/Omega receiver implemented on a TMS320C30-microprocessor-based SPECTRUM plug-in board installed in a PC-compatible portable computer is presented. The system also requires an external antenna, pre-amp, and frequency reference. The SPECTRUM board digitizes the RF signal to 16 b and then digitally mixes with the sines and cosines of the three Russian frequencies plus 10.2, 11-1/3, and 13.6 kHz. The mixer outputs are low-pass filtered, and the comb filters are implemented for the respective epochs. The computer accesses and processes the comb filter outputs, calculating and logging signal phase and amplitude. The design allows for easy future expansion to include unique and VLF communication frequencies     

Chemical evolution of RNA under hydrothermal conditions and the role of thermal copolymers of amino acids for the prebiotic degradation and formation of RNA.

The roles of thermal copolymers of amino acids (TCAA) were studied for the prebiotic degradation of RNA. A weak catalytic ability of TCAA consisted of Glu, L-Ala, L-Val, L-Glu, L-Asp, and optionally L-His was detected for the cleavage of the ribose phosphodiester bond of a tetranucleotide (5'-dCrCdGdG) in aqueous solution at 80 degees C. The rate constants of the disappearance of 5'-dCrCdGdG were determined in aqueous solutions using different pH buffer and TCAA. The degradation rates were enhanced 1.3-3.0 times in the presence of TCAA at pH 7.5 and 8.0 at 80 degrees C, while the hydrolysis of oligoguanylate (oligo(G)) was accelerated about 1.6 times at pH 8.0. A weak inhibitory activity for the cleavage of oligo(G) was detected in the presence of 0.055 M TCAA-Std. On the other hand, our recent study on the influences of TCAA for the template-directed reaction of oligo(G) on a polycytidylic acid template showed that TCAA has an acceleration activity for the degradation of the activated nucleotide monomer and an acceleration activity for the formation of G5' ppG capped oligo(G). This series of studies suggest that efficient and selective catalytic or inhibitory activities for either the degradation or formation of RNA under hydrothermal conditions could have hardly emerged from the simple thermal condensation products of amino acids. A scenario is going to be deduced on the chemical evolution of enzymatic activities and RNA molecules concerning hydrothermal earth conditions.     

Hypergravity modulates behavioral nociceptive responses in rats.

Hypergravity (2G) exposure elevated the nociceptive threshold (pain suppression) concomitantly with evoked neuronal activity in the hypothalamus. Young Wistar male rats were exposed to 2G by centrifugal rotation for 10 min. Before and after 2G exposure, the nociceptive threshold was measured as the withdrawal reflex by using the von Frey type needle at a total of 8 sites of each rat (nose, four quarters, upper and lower back, tail), and then rats were sacrificed. Fos expression was examined immunohistochemically in the hypothalamic slices of the 2G-treated rats. When rats were exposed to 2G hypergravity, the nociceptive threshold was significantly elevated to approximately 150 to 250% of the 1G baseline control levels in all the examination sites. The 2G hypergravity remarkably induced Fos expression in the paraventricular and arcuate nuclei of the hypothalamus. The analgesic effects of 2G hypergravity were attenuated by naloxone pretreatment. Data indicate that hypergravity induces analgesic effects in rats, mediated through hypothalamic neuronal activity in the endogenous opioid system and hypothalamo-pituitary-adrenal axis.     

Aquatic animal research in space station and its issues--focus on support technology on nitrate toxicity.

We studied the effects of accumulated nitrate in water on the spawning, hatching and development of medaka using a simple nitrifying filter and a combined filter having both nitrifying and denitrifying capabilities. A nitrate concentration of 100 mg NO3(-)-N/L was clearly of lethal toxicity to fish when they were exposed to nitrate in both adult and the growing phases. A nitrate concentration of 75 mg NO3(-)-N/L reduced the fertilization rate, delayed the hatching time and reduced the hatching rate of the eggs laid by adults and decreased the growth rate of juveniles. In addition, nitrate accumulations as low as 50 mg NO3(-)-N/L remarkably retarded spawning and lowered the number of eggs laid by fish exposed in the juvenile phase. The effects on the reproduction system may be initiated by a low concentration, approximately 30 mg NO3(-)-N/L.     

Re-analysis of the cosmic ray ground level enhancement of 4 May 1960.

The relativistic solar particle event of 4 May 1960, resulting in a cosmic ray ground level enhancement, occurred well before modern analysis techniques were available. We have located surviving data from 23 neutron monitors and have used these to estimate the spectrum, mean arrival direction and particle pitch angle distribution as the event progressed. We find that the apparent particle arrival direction was at equatorial latitudes, over northern South America, in contrast to contemporary analyses that proposed it to be over North America. Our modified power law spectra are broadly consistent with earlier results. Data from stations above sea level need to be corrected for altitude using a two-attenuation length technique. The standard method involves comparison of data from two relatively close stations at significantly different altitude. We have shown that this method may be unreliable in cases, such as this, of quite sharp anisotropy.     

Applying automation to spacecraft mission operations

This study was initially undertaken to understand how commonalities among the application of proven automation processes such as aircraft control, nuclear power generation, auto manufacturing, etc. could be applied to spacecraft operations at NASA. These industries applied automation to reduce human repetitive task and mitigate risk, rather than create complete "lights out" operations as was the goal at NASA.