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Harrison, G.

Publications and source records attributed to Harrison, G..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Retinal changes in rats flown on Cosmos 936 - A cosmic ray experiment

Ten rats, five centrifuged during flight to simulate gravity and five stationary in flight and experiencing hypogravity, orbited the Earth. No differences were noted between flight-stationary and flight-centrifuged animals, but changes were seen between these two groups and ground controls. Morphological alterations were observed comparable to those in the experiment flown on Cosmos 782 and to the retinal cells exposed to high-energy particles at Berkeley. Affected cells in the outer nuclear layer showed swelling, clearing of cytoplasm, and disruption of the membranes. Tissue channels were again found, similar to those seen on 782. After space flight, preliminary data indicated an increase in cell size in montages of the nuclear layer of both groups of flight animals. This experiment shows that weightlessness and environmental conditions other than cosmic radiation do not contribute to the observed damage of retinal cells.

Philpott, D. E.↗
NASA NTRS1979

Modification of a Kowa RC-2 fundus camera for self-photography without the use of mydriatics

Research on retinal circulation during space flight required the development of a simple technique to provide self monitoring of blood vessel changes in the fundus without the use of mydriatics. A Kowa RC-2 fundus camera was modified for self-photography by the use of a bite plate for positioning and cross hairs for focusing the subject's retina relative to the film plane. Dilation of the pupils without the use of mydriatics was accomplished by dark-adaption of the subject. Pictures were obtained without pupil constriction by the use of a high speed strobe light. This method also has applications for clinical medicine.

Philpott, D. E.↗
NASA NTRS1978

Effects of Radiation on Rat Retina after 18 days of Space Flight

Although cumulative effects an retina from low-dose radiation during prolonged spaceflight are not known, ary impairment of vision could set limits for spaceflight duration. Cosmic rays are now considered to be the cause of the "light flashes" seen during spaceflight by activating retina cells as they pass through the photoreceptors. Previous studies have also shown retinal cellular alterations and cell necrosis from high-energy, particle (HZE) radiation. Ten rats, 5 centrifuged during flight (FC) to simulate gravity and 5 in-flight stationary (FS) experiencing hypogravity, orbited Earth for 18.5 days on Cosmos 936. The animals were sacrificed 25 days post-recovery and the eyes flown to Ames Res. Ctr. The pattern of cell necrosis in the retinas from the FC group showed the same response to radiation as the FS. This would indicate that hypogravity was not a factor in the observed results. Also the cellular response in the retinas exposed in the Berkeley accelerator again matched both the FC and FS eyes. Thus all three conditions provide comparable changes and indicate HZE particles as the possible cause of the cellular alterations, channels, and breakdown.

Philpott, D.↗
NASA NTRS1978

Cosmic ray effects on the eyes of rats flown on Cosmos no. 782, Experiment K-007

A study was undertaken to determine if, and to what extent, pathological damage results from high-energy particles (HZE) transversing the eye. Light flashes experienced by space travellers indicate that HZE do indeed pass through and activate the retina, but whether actual biological damage occurs has not been investigated thoroughly. Thus, autopsies were performed on the eyes of rats which has been flown in Cosmos 782 satellite for 19.5 days. Comparisons with a control sample subjected to 1000 rads of Ar and Ne radiation show that pathological damage, when it occurs, affects the nucleus of the retina; simple light flashes are not thought to indicate a pathology, and result from activation of (but not damage to) the retina's outer segments.

Philpott, D. E.↗
NASA NTRS1973

Ultrastructural pathogenesis of lesions produced by exposure to oxygen difluoride with correlative light microscopy

The lungs of rats exposed to OF2 were examined by light and electron microscopy. The exposures were for 30 to 60 minutes to an average of 4.5 ppm OF2, the minimal lethal dose. Animals were sacrificed after 30 (group 1) and 60 minutes (group 2) exposure and 1 (group 3) and 2 (group 4) hours following 60 minutes exposure. Mild gross changes were observed in groups 3 and 4, but no light microscopic lesions were found. Alterations were noted in all four groups using electron microscopy. These were mostly indicative of fluid change and consisted of blebbing of the endothelial and epithelial layers of the alveolocapillary wall and rarification of the cytoplasm of these cells. The lamellar bodies of the Type II cells showed an increasing and consistent loss of matrix structure and density. These fine structural changes increased in quantity and severity as time of exposure or post-exposure period increased. (Modified author abstract)

Harrison, G.↗
NASA NTRS1972

The role of compressional viscoelasticity in the lubrication of rolling contacts.

A simple model for the time-dependent volume response of a liquid to an applied pressure step is used to calculate the variation with rolling speed of the traction coefficient in a rolling contact system. Good agreement with experimental results is obtained at rolling speeds above 50 in/sec. At lower rolling speeds a very rapid change in the effective viscosity of the lubricant is predicted. This behavior, in conjunction with shear rate effects, is shown to lead to large errors when experimental data are extrapolated to zero rolling speed.

Harrison, G.↗