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Biomedical subjects

E V Benton

Publications and source records attributed to E V Benton.

At least 19 recordsLinked to original sources
PubMed1989

Radiation effects in Caenorhabditis elegans, mutagenesis by high and low LET ionizing radiation.

The nematode C. elegans was used to measure the effectiveness of high-energy ionized particles in the induction of 3 types of genetic lesions. Recessive lethal mutations in a 40-map unit autosomal region, sterility, and X-chromosome nondisjunction or damage were investigated. Induction rates were measured as a function of linear energy transfer, LET infinity, for 9 ions of atomic number 1-57 accelerated at the BEVALAC accelerator. Linear kinetics were observed for all 3 types of lesions within the dose/fluence ranges tested and varied strongly as a function of particle LET infinity. Relative Biological Effectiveness (RBE) values of up to 4.2 were measured and action cross sections were calculated and compared to mutagenic responses in other systems.

Animals↗
PubMed1985

The effect of high energy (HZE) particle radiation (40Ar) on aging parameters of mouse hippocampus and retina.

Eight month old C57BL6 mice were exposed (head only) to 0.5 rad or 50 rads of Argon particles at the Lawrence Berkeley Radiation Facility, CA. Neuromotor performance was assessed monthly for six months beginning twelve weeks post-irradiation using a "string test". The decline in motor performance was dose-related and none of the animals was able to complete the task after four months of testing. Morphological changes were monitored six and twelve months post-irradiation by light and electron microscopy. The synaptic density in the CA-1 area of the hippocampus decreased six and twelve months after irradiation. The decrease after twelve months was less than after six months. The width of the outer nuclear layer (ONL) of the retina increased with increasing dose. The number of blood vessels between the ONL and the ganglion layer decreased twelve months after irradiation and this area did not show significant accumulation of age pigment.

Aging↗
PubMed1979

Effects of high-LET neon (20Ne) particle radiation on the brain, eyes and other head structures of the pocket mouse: a histological study.

A study was made of tissues from 130 pocket mice after a single head-only exposure to high-LET 20Ne particle radiation at 1000, 100 or 10 rad (nominal surface dose) with the view of obtaining base"line data regarding the effectiveness of HZE (cosmic-ray) particles during spaceflight. First seen at 2-3 weeks after exposure, necrotic neurons in the cerebrum reached peak incidence (0 . 04 per cent at 1000 rad, 0 . 003 per cent at 100 rad and less than 0 . 0005 per cent at 10 rad) after 4-5 weeks and decreased to low levels thereafter. Incidence in the cerebellum was lower. Neuroglia, cells of the subependymal matrix and dentate gyrus precursor cells suffered acute damage at 1000 and at 100 rad. At 1000 rad, enlarged hyperchromatic neuroglia, first noted at 3 weeks, increased in number up to 7 months, then declined. Alterations in the retina and olfactory epithelium were seen at 1000 rad, and reaction in the scalp at 100 rad. Damage was incurred by dentinoblasts at 10 rad. Changes similar to those observed in pocket mice were found in the brains of gerbils and C57B1 mice.

Animals↗
PubMed1976

Effects of high-LET particles (40A) on the brain of Drosophila melanogaster.

To investigate the effects of galactic heavy particles on nervous tissue, Drosophila melanogaster flies were exposed to 40A from the Super-HILAC accelerator at the Lawrence Berkeley Laboratory. The energy of the particles reaching the Drosophila neurons was 4-8 MeV/nucleon, and the fluence ranged from 6 X 10(4) to 8 X 10(7) particles/cm2. Thirty-five days after irrdiation at the higher fluences, extensive tissue fragmentation and cysts were found. At fluences as low as one hit/two cell bodies (about 5 X 10(6)) and one hit/90 cell bodies (about 9 X 10(4) particles/cm2 or 21 rad average dose) swelling of neuronal cytoplasm and focally fragmented membranes were noted; at fluences ranging from one hit/six to one hit/135 cell bodies, there was frequently a marked increase in glial lamellae around nerve-cell processes, which often had degenerative features. These findings support the view that single hits by heavy particles may injure nervous tissue.

Animals↗
PubMed1975

Heavy cosmic-ray exposure of Apollo astronauts.

A comprehensive study of the heavy-particle cosmic-ray exposure received by the individual astronauts during the nine lunar Apollo missions reveals a significant variation in the exposure as a function of shielding and the phase of the solar cycle. The data are useful in planning for future long-range missions and in estimating the expected biological damage.

Adult↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: I. Project BIOCORE (M212), a biological cosmic ray experiment: procedures, summary, and conclusions.

The primary objective of the experiment was to determine whether a specific portion of the high Z-high energy (HZE)* galactic cosmic ray particle spectrum, especially particles with Z greater than or equal to 6, can produce microscopically visible injury of brain and eye tissues. Pocket mice (Perognathus longimembris), obtained from the California desert, were selected as the biological target. Five of these mice were flown on Apollo XVII. Not only the brain and eyes but also many other tissues of these animals were studied for evidence of cosmic ray particle damage. The lack of prior experimental evidence as to the character of the potential injury induced by HZE particles required reliance on the physical characteristics of particle radiation in ascertaining the probable nature of the injruy. These characteristics and the key aspects of the experiment are summarized in this paper. Subsequent articles in this special supplement give details of the biological, engineering, and dosimetric aspects of BIOCORE together with the results.

Animals↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: III. Dosimeter design, construction, and implantation.

To detect the passage of cosmic ray particles through the heads of the pocket mice during the Apollo XVII flight, a "monitor" (dosimeter) composed of plastics was prepared and implanted under the scalp. The monitor was mounted on a platform, the undersurface of which fitted the contour of the skull. Numerous tests were run to assure that the presence of the monitor assembly beneath the scalp would be compatible with the well-being of the mice and that the capacity of the monitor to detect the traversal of cosmic ray particles would be preserved over the several weeks during which it would remain under the scalp.

Animals↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: VII. Cosmic ray particle dosimetry and trajectory tracing.

Five pocket mice (Perognathus longimembris) were flown on Apollo XVII, each with a solid-state (plastic) nuclear track detector implanted beneath its scalp. The subscalp detectors were sensitive to HZE cosmic ray particles with a LET larger than or equal to 0.15 million electron volts per micrometer (MeV/mjm). A critical aspect of the dosimetry of the experiment involved tracing individual particle trajectories through each mouse head from particle tracks registered in the individual subscalp detectors, thereby establishing a one-to-one correspondence between a trajectory location in the tissue and the presence or absence of a lesion. The other major aspect was the identification of each registered particle. An average of 16 particles with Z larger than or equal to 6 and 2.2 particles with Z larger than or equal to 20 were found per detector. The track density, 29 tracks/cm2, when adjusted for detection volume, was in agreement with the photographic emulsion data from an area dosimeter located next to the flight package.

Animals↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVIII: VII: results of scalp examination.

The scalps of the four pocket mice that were recovered alive from the Apollo XVII flight contained acute focal lesions in the epidermis and an inflammatory reaction in the subjacent dermis and subcutaneous tissue. Hair follicles were focally damaged in three of the four mice. There were 13 scalp lesions singled out in the four flight mice because of histological features that distinguished them from changes observed in the scalps of the control mice. There was only one possible coincidence between a lesion and the trajectory of a cosmic ray particle registered in a subscalp dosimeter. There is, however, a possibility that at least some lesions were produced by unregistered particles.

Animals↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: IX Results of examination of the nasal mucosa.

The olfactory epithelium, but not the nasal respiratory epithelium, of the four pocket mice (Perognathus longimembris) that survived their flight on Apollo XVII showed both diffuse alterations and numerous disseminated focal lesions. The olfactory mucosa of the mouse that died during flight was also affected, but to a minor degree insofar as could be determined. All this was in contrast to the normal appearance of the olfactory mucosa of the numerous control animals. A number of possible causes were considered: systemic or regional infection; inhaled particulate material (seed dust); by-products from the KO2 bed in aerosol or particulate form; gas contaminants originating in the flight package; volatile substances from the dead mouse; weightlessness; and cosmic ray particle radiation. Where feasible, studies were conducted in an effort to rule in or rule out some of these potentially causative factors. No definitive conclusions were reached as to the cause of the lesions in the flight mice.

Aerosols↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: X. Results of ear examination.

In the five pocket mice flown on Apollo XVII, no evidence was found that the inner ear had been damaged, though poor fixation precluded detailed study. On the other hand, the middle ear cavity was involved in all the mice, hemorrhage having occurrred in response to excursions in pressure within the canister that housed the mice during their flight. The same occurred in flight control mice which had been subjected to pressure excursions of much the same magnitude. A greater degree of exudation into air cells and greater leukotaxis were noted in the flight animals than in the control animals. There was no increase in leukocyte population along the paths of the 23 cosmic ray particles registered in the subscalp dosimeters that traversed the middle ear cavities of the flight mice. The increased exudation and the greater response by leukocytes in the flight mice may have been causally related to the lesions found in their olfactory mucosa but there were no data in support of this possibility.

Animals↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: XI. Results of eye examination.

Five pocket mice (Perognathus longimembris) were flown on Apollo XVII, and four survived. All the eyes, except one eye from the dead flight mouse, were examined histologically. In the four surviving mice, a total of five cosmic ray particles which had registered in the subscalp particle detectors had trajectories that intersected the eyes. Four of them (Z equal to 6-9 for three of the particles and Z larger than or equal to 10 for the fourth) most likely went through the head before reaching the particle detector, while the thindown direction of the fifth (Z larger than or equal to 10) was not determinable. The retinas of the flight animals were found free from histological alterations such as might have been expected from encounters with cosmic ray particles.

Animals↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: XII. Results of examination of the calvarium, brain, and meninges.

Tissue reactions were found around the monitor (dosimeter) assemblies that had been implanted beneath the scalp of the five pocket mice that flew on Apollo XVII. Mitosis in the dentate gyrus of the hippocampal formation was considerably reduced in comparison with that in control animals. Otherwise the brain tissue as well as the menings in the flight animals appeared unaltered. Since the animals were exposed primarily to high Z-high energy (HZE) cosmic ray particles at the lower end of the high LET spectrum, the lack of changes in the brain cannot be taken as evidence that the brain will suffer no damage from the heavier HZE particles on prolonged manned missions.

Animals↗