SEARCH · Search NASA

Results for “RABBIT”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10

All sources NASA NTRS DOE OSTI

NASA NTRS1992

Late cataractogenesis in primates and lagomorphs after exposure to particulate radiations

Results are presented from a study in which regular examinations of cataractogenic development were conducted since 1987 in monkeys that were exposed in 1969, at the age of about 2 years, to low doses of 'mixed-energy' protons (10 and 110 MeV). The results of comparisons with age-matched controls showed that the cataractogenic patterns observed in the exposed monkeys are consistent with those observed in other groups of monkeys that were exposed at similar ages in 1964 and 1965 to protons of different energies (Lett et al., 1986, 1988, 1989, and 1991). Comparisons were also made among recent results from different groups of primates and from New Zealand white rabbits that were exposed when young to Fe-56 and were monitored continuously thereafter.

Cox, A. B.↗

NASA NTRS1991

A study of lens opacification for a Mars mission

A method based on risk-related cross sections is used to estimate risks of 'stationary' cataracts caused by radiation exposures during extended missions in deep space. Estimates of the even more important risk of late degenerative cataractogenesis are made on the basis of the limited data available. Data on lenticular opacification in the New Zealand white rabbit, an animal model from which such results can be extrapolated to humans, are analyzed by the Langley cosmic ray shielding code (HZETRN) to generate estimates of stationary cataract formation resulting from a Mars mission. The effects of the composition of shielding material and the relationship between risk and LET are given, and the effects of target fragmentation on the risk coefficients are evaluated explicitly.

Shinn, J. L.↗

NASA NTRS1991

LET analyses of biological damage during solar particle events

The effects of nuclear reactions on integral low-linear-energy-transfer (LET) protons spectra are studied, behind typical levels of spacecraft and body shielding, for the historically largest flares using the high-energy transport code BRYNTRN in conjunction with several biological damage models. The cellular track model of Katz provides an accurate description of cellular damage from heavy ion exposure. The track model is applied with BRYNTRN to provide a LET decomposition of survival and transformation rates for solar proton events. In addition, a fluence-based risk coefficient formalism is used to estimate Harderian gland-tumor induction in rodents and cataractogenesis in rabbits from solar flares, and a LET analysis is used to assess the relative contribution from target fragments on these biological endpoints.

Cucinotta, Francis A.↗

NASA NTRS1993

High specific energy, high capacity nickel-hydrogen cell design

A 3.5 inch rabbit-ear-terminal nickel-hydrogen cell has been designed and tested to deliver high capacity at a C/1.5 discharge rate. Its specific energy yield of 60.6 wh/kg is believed to be the highest yet achieved in a slurry-process nickel-hydrogen cell, and its 10 C capacity of 113.9 AH the highest capacity yet made at a discharge rate this high in the 3.5 inch diameter size. The cell also demonstrated a pulse capability of 180 amps for 20 seconds. Specific cell parameters, performance, and future test plans are described.

Wheeler, James R.↗

NASA NTRS1992

Perceptual bias for forward-facing motion

When an occluded horizontal row of shapes is shifted laterally, apparent motion can be experienced in either the leftward or the rightward direction. Four experiments provide evidence for a motion bias in the direction that shapes appear to face. The bias tended to be largest when directionality was specified geometrically (e.g., triangles), next largest when it was specified biologically (e.g., mice), and absent when it was specified calligraphically (e.g., letter R). The bias increased parametrically as a function of triangle pointedness and was consistent with the directional interpretation of an ambiguous duck-rabbit. The results support the existence of a cognitively specified forward-facing attribute that can influence experienced direction of motion.

Mcbeath, Michael K.↗

NASA NTRS1993

High specific energy, high capacity nickel-hydrogen cell design

A 3.5 inch rabbit-ear-terminal nickel-hydrogen cell was designed and tested to deliver high capacity at steady discharge rates up to and including a C rate. Its specific energy yield of 60.6 wh/kg is believed to be the highest yet achieved in a slurry-process nickel-hydrogen cell, and its 10 C capacity of 113.9 AH the highest capacity yet of any type in a 3.5 inch diameter size. The cell also demonstrated a pulse capability of 180 amps for 20 seconds. Specific cell parameters and performance are described. Also covered is an episode of capacity fading due to electrode swelling and its successful recovery by means of additional activation procedures.

Wheeler, James R.↗

NASA NTRS1994

SAFT nickel hydrogen cell cycling status

An overview of the NiH2 cell development is given. The NiH2 SAFT system is an electrochemical (single or dual) stack (IPV). The stack is mounted in an hydroformed Inconel 718 vessel operating at high pressure, equipped with 'rabbit ears' ceramic brazed electrical feedthroughs. The cell design is described: positive electrode, negative electrode, and stack configuration. Overviews of low earth orbit and geostationary earth orbit cyclings are provided. DPA results are also provided. The cycling and DPA results demonstrate that SAFT NiH2 is characterized by high reliability and very stable performances.

Borthomieu, Yannick↗

NASA NTRS1994

Does training-induced orthostatic hypotension result from reduced carotid baroreflex responsiveness?

As manned space travel has steadily increased in duration and sophistication, the answer to a simple, relevant question remains elusive. Does endurance exercise training - high intensity rhythmic activity, performed regularly for extended periods of time - alter the disposition to, or severity of, postflight orthostatic hypotension? Research results continue to provide different views; however, data are difficult to compare because of the following factors that vary between investigations: the type of orthostatic stress imposed (+Gz, lower body negative pressure (LBNP), head-up tilt); pretest perturbations used (exercise, heat exposure, head-down tilting, bed rest, water immersion, hypohydration, pharmacologically-induced diuresis); the length of the training program used in longitudinal investigations (days versus weeks versus months); the criteria used to define fitness; and the criteria used to define orthostatic tolerance. Generally, research results indicate that individuals engaged in aerobic exercise activities for a period of years have been reported to have reduced orthostatic tolerance compared to untrained control subjects, while the results of shorter term longitudinal studies remain equivocal. Such conclusions suggest that chronic athletic training programs reduce orthostatic tolerance, whereas relatively brief (days to weeks) training programs do not affect orthostatic tolerance to any significant degree (increase or decrease). A primary objective was established to identify the alterations in blood pressure control that contribute to training-induced orthostatic hypotension (TIOH). Although any aspect of blood pressure regulation is suspect, current research has been focused on the baroreceptor system. Reductions in carotid baroreflex responsiveness have been documented in exercise-trained rabbits, reportedly due to an inhibitory influence from cardiac afferent, presumably vagal, nerve fibers that is abolished with intrapericardiac denervation. The purpose of this investigation was to attempt to determine if similar relationships existed in men with varied levels of fitness, using maximal aerobic power, VO2 max, as the marker of fitness.

Pawelczyk, James A.↗

NASA NTRS1995

Unique features of a new nickel-hydrogen 2-cell CPV

Two-cell nickel-hydrogen common pressure vessel (CPV) units with some unusual design features have been successfully built and tested. The features of interest are half-normal platinum loading for the negative electrodes, the use of rabbit-ear terminals for a CPV unit, and the incorporation of a wall wick. The units have a nominal capacity of 20 Ah and are 3.5 inches in diameter. Electric performance data are provided. The data support the growing viability of the two-cell CPV design concept.

Wheeler, James R.↗

NASA NTRS1994

Computerized In Vitro Test for Chemical Toxicity Based on Tetrahymena Swimming Patterns

An apparatus and a method for rapidly determining chemical toxicity have been evaluated as an alternative to the rabbit eye initancy test (Draize). The toxicity monitor includes an automated scoring of how motile biological cells (Tetrahymena pyriformis) slow down or otherwise change their swimming patterns in a hostile chemical environment. The method, called the motility assay (MA), is tested for 30 s to determine the chemical toxicity in 20 aqueous samples containing trace organics and salts. With equal or better detection limits, results compare favorably to in vivo animal tests of eye irritancy.

Noever, David A.↗

NASA NTRS1997

Modular Manufacturing Simulator: Users Manual

The Modular Manufacturing Simulator (MMS) has been developed for the beginning user of computer simulations. Consequently, the MMS cannot model complex systems that require branching and convergence logic. Once a user becomes more proficient in computer simulation and wants to add more complexity, the user is encouraged to use one of the many available commercial simulation systems. The (MMS) is based on the SSE5 that was developed in the early 1990's by the University of Alabama in Huntsville (UAH). A recent survey by MSFC indicated that the simulator has been a major contributor to the economic impact of the MSFC technology transfer program. Many manufacturers have requested additional features for the SSE5. Consequently, the following features have been added to the MMS that are not available in the SSE5: runs under Windows, print option for both input parameters and output statistics, operator can be fixed at a station or assigned to a group of stations, operator movement based on time limit, part limit, or work-in-process (WIP) limit at next station. The movement options for a moveable operators are: go to station with largest WIP, rabbit chase where operator moves in circular sequence between stations, and push/pull where operator moves back and forth between stations. This user's manual contains the necessary information for installing the MMS on a PC, a description of the various MMS commands, and the solutions to a number of sample problems using the MMS. Also included in the beginning of this report is a brief discussion of technology transfer.

Source record↗

NASA NTRS1994

A Study of Parameters Affecting Fibroblast Morphology in Response to an Applied Mechanical Force

A precisely controlled stretch/relaxation regimen (20% elongation at 6.6 cycles/min) was applied to normal human fetal, neonatal and aged dermal fibroblasts cultured on flexible membranes. Culture conditions included poly (NH2) or collagen type I coated substrate membranes; control cultures were grown on the same pliable material in the absence of applied stretch. Direct observation and immunofluorescence analyses revealed a progressive change in cell body orientation limited to the stretched dermal fibroblast cultures. Monolayers gradually (over 4 days) acquired a symmetric, radial distribution equivalent to the biaxial array of the applied force. At high seeding density, alignment was inhibited in the fetal cell cultures. This cell strain required collagen type I coating for optimal attachment to the flexible membrane, preferring growth in three-dimensional cell 'balls' on the poly(NH2) coated substrate. Neonatal cells also required the collagen type I coating, but both neonatal and aged dermal fibroblasts aligned efficiently at all seeding densities examined. The randomly oriented neonatal cells on the unstretched control membranes spontaneously detached at confluence, as a single cell sheet. Their aligned counterparts did not detach until the applied stretch stimulus was removed. Low concentrations of cytochalasin D (62.5 ng/ml) disrupted the stretch-related alignment response. Rhodamine phalloidin staining visualized fewer actin stress fibers in stretched, aligned cells than in controls. Both intercellular interactions and cytoskeletal integrity mediate the response to mechanical strain. Normal rabbit corneal stroma fibroblasts (NRC) were also analyzed, and failed to orient under these conditions. This cell type may require a different regimen, or a longer time period, to demonstrate alignment behavior. Supported by NASA Space Biology RTOP 199-40-22 and the NASA-ARC Director's Discretionary Fund.

Grymes, Rosalind A.↗

NASA NTRS1995

Integrin-extracellular matrix interactions in connective tissue remodeling and osteoblast differentiation

The differentiaton of bone cells is a complex multistep process. Bone is somewhat unusual in that it is very actively and continually remodeled in the adult and that maintenance of its mass in the mature organism is exquisitely sensitive to mechanical as well as chemical signals. Bone is also unique because it consists of a very large amount of extracellular matrix (ECM) that is mineralized. The integrin family of ECM receptors has been shown to play an important role in tissue morphogenesis in several systems. Our studies on the regulation of matrix remodeling enzymes by integrins in rabbit synovial fibroblasts show that two b1 integrin fibronectin (FN) receptor complexes (alpha 5 beta 1 and alpha 4 beta 1) cooperate in detecting subtle changes in the composition of the ECM. As a result of signal transduction by these integrins, the levels of mRNA and protein for several members of the metalloproteinase family are regulated in these cells. We have also used antibody and RGD peptide perturbation studies to determine the significance of cell/ECM interactions to normal osteogenesis. We found that interactions between the cell binding domain of FN and integrins are required for both normal morphogenesis and gene expression in cultured osteoblasts that differentiate to form bone-like tissue in culture. These data lead us to propose that beta 1 integrins play an important role in osteoblast differentiation as well as in bone remodeling.

NASA Discipline Number 26-10↗

NASA NTRS1988

Evidence against the involvement of ionically bound cell wall proteins in pea epicotyl growth

Ionically bound cell wall proteins were extracted from 7 day old etiolated pea (Pisum sativum L. cv Alaska) epicotyls with 3 molar LiCl. Polyclonal antiserum was raised in rabbits against the cell wall proteins. Growth assays showed that treatment of growing region segments (5-7 millimeters) of peas with either dialyzed serum, serum globulin fraction, affinity purified immunoglobulin, or papain-cleaved antibody fragments had no effect on growth. Immunofluorescence microscopy confirmed antibody binding to cell walls and penetration of the antibodies into the tissues. Western blot analysis, immunoassay results, and affinity chromatography utilizing Sepharose-bound antibodies confirmed recognition of the protein preparation by the antibodies. Experiments employing in vitro extension as a screening measure indicated no effect upon extension by antibodies, by 50 millimolar LiCl perfusion of the apoplast or by 3 molar LiCl extraction. Addition of cell wall protein to protease pretreated segments did not restore extension nor did addition of cell wall protein to untreated segments increase extension. It is concluded that, although evidence suggests that protein is responsible for the process of extension, the class(es) of proteins which are extracted from pea cell walls with 3 molar LiCl are probably not involved in this process.

NASA Program Space Biology↗

NASA NTRS1992

Gene activity during germination of spores of the fern, Onoclea sensibilis. Cell-free translation analysis of mRNA of spores and the effect of alpha-amanitin on spore germination

Poly(A)-RNA fractions of dormant, dark-imbibed (non-germinating) and photoinduced (germinating) spores of Onoclea sensibilis were poor templates in the rabbit reticulocyte lysate protein synthesizing system, but the translational efficiency of poly(A)+RNA was considerably higher than that of unfractionated RNA. Poly(A)+RNA isolated from photoinduced spores had a consistently higher translational efficiency than poly(A)+RNA from dark-imbibed spores. Analysis of the translation products by one-dimensional polyacrylamide gel electrophoresis showed no qualitative differences in the mRNA populations of dormant, dark-imbibed, and photoinduced spores. However, poly(A)+RNA from dark-imbibed spores appeared to encode in vitro fewer detectable polypeptides at a reduced intensity than photoinduced spores. A DNA clone encoding the large subunit of maize ribulose bisphosphate carboxylase hybridized at strong to moderate intensity to RNA isolated from dark-imbibed spores, indicating the absence of mRNA degradation. Although alpha-amanitin did not inhibit the germination of spores, the drug prevented the elongation of the rhizoid and protonemal initial with a concomitant effect on the synthesis of poly(A)+RNA. These results are consistent with the view that some form of translational control involving stored mRNA operates during dark-imbibition and photoinduced germination of spores.

NASA Discipline Number 29-20↗

NASA NTRS1992

Development and use of domain-specific antibodies in a characterization of the large subunits of soybean photosystem 1

The molecular architecture of the soybean photosystem 1 reaction center complex was examined using a combination of surface labeling and immunological methodology on isolated thylakoid membranes. Synthetic peptides (12 to 14 amino acids in length) were prepared which correspond to the N-terminal regions of the 83 and 82.4 kDa subunits of photosystem 1 (the PsaA and PsaB proteins, respectively). Similarly, a synthetic peptide was prepared corresponding to the C-terminal region of the PsaB subunit. These peptides were conjugated to a carrier protein, and were used for the production of polyclonal antibodies in rabbits. The resulting sera could distinguish between the PsaA and PsaB photosystem 1 subunits by Western blot analysis, and could identify appropriate size classes of cyanogen bromide cleavage fragments as predicted from the primary sequences of these two subunits. When soybean thylakoid membranes were surface-labeled with N-hydroxysuccinimidobiotin, several subunits of the complete photosystem 1 lipid/protein complex incorporated label. These included the light harvesting chlorophyll proteins of photosystem 1, and peptides thought to aid in the docking of ferredoxin to the complex during photosynthetic electron transport. However, the PsaA and PsaB subunits showed very little biotinylation. When these subunits were examined for the domains to which biotin did attach, most of the observed label was associated with the N-terminal domain of the PsaA subunit, as identified using a domain-specific polyclonal antisera.

NASA Program NSCORT↗

NASA NTRS1992

Antipeptide antibodies that can distinguish specific subunit polypeptides of glutamine synthetase from bean (Phaseolus vulgaris L.)

The amino acid sequences of the beta and gamma subunit polypeptides of glutamine synthetase from bean (Phaseolus vulgaris L.) root nodules are very similar. However, there are small regions within the sequences that are significantly different between the two polypeptides. The sequences between amino acids 2 and 9 and between 264 and 274 are examples. Three peptides (gamma 2-9, gamma 264-274, and beta 264-274) corresponding to these sequences were synthesized. Antibodies against these peptides were raised in rabbits and purified with corresponding peptide-Sepharose affinity chromatography. Western blot analysis of polyacrylamide gel electrophoresis of bean nodule proteins demonstrated that the anti-beta 264-274 antibodies reacted specifically with the beta polypeptide and the anti-gamma 264-274 and anti-gamma 2-9 antibodies reacted specifically with the gamma polypeptide of the native and denatured glutamine synthetase. These results showed the feasibility of using synthetic peptides in developing antibodies that are capable of distinguishing proteins with similar primary structures.

NASA Program NSCORT↗

NASA NTRS1996

Quantitative assessment of the cataractogenic potential of very low doses of neutrons

We report on the prevalence and relative biological effectiveness (RBE) for various stages of lens opacification in rats induced by very low doses (2 to 250 mGy) of medium-energy (440 keV) neutrons, compared to those for X rays. Neutron doses were delivered either in a single fraction or in four separate fractions and the irradiated animals were followed for over 100 weeks. At the highest observed dose (250 mGy) and at early observation times, there was evidence of an inverse dose-rate effect; i.e., a fractionated exposure was more potent than a single exposure. Neutron RBEs relative to X rays were estimated using a non-parametric technique. The results were only weakly dependent on time postirradiation. At 30 weeks, for example, 80% confidence intervals for the RBE of acutely delivered neutrons relative to X rays were 8-16 at 250 mGy, 10-20 at 50 mGy, 50-100 at 10 mGy and 250-500 at 2 mGy. The results are consistent with the estimated neutron RBEs in Japanese A-bomb survivors, though broad confidence bounds are present in the Japanese results. Our findings are also consistent with data reported earlier for cataractogenesis induced by heavy ions in rats, mice, and rabbits. We conclude from these results that, at very low doses (<10 mGy), the RBE for neutron-induced cataractogenesis is considerably larger than the RBE of 20 commonly used, and use of a significantly larger value for calculating equivalent dose would be prudent.

NASA Discipline Radiation Health↗