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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.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Novel Extracellular Electron Transfer Channels in a Gram-Positive Thermophilic Bacterium

Biogenic transformation of Fe minerals, associated with extracellular electron transfer (EET), allows microorganisms to exploit high-potential refractory electron acceptors for energy generation. EET-capable thermophiles are dominated by hyperthermophilic archaea and Gram-positive bacteria. Information on their EET pathways is sparse. Here, we describe EET channels in the thermophilic Gram-positive bacterium Carboxydothermus ferrireducens that drive exoelectrogenesis and rapid conversion of amorphous mineral ferrihydrite to large magnetite crystals. Microscopic studies indicated biocontrolled formation of unusual formicary-like ultrastructure of the magnetite crystals and revealed active colonization of anodes in bioelectrochemical systems (BESs) by C. ferrireducens . The internal structure of micron-scale biogenic magnetite crystals is reported for the first time. Genome analysis and expression profiling revealed three constitutive c -type multiheme cytochromes involved in electron exchange with ferrihydrite or an anode, sharing insignificant homology with previously described EET-related cytochromes thus representing novel determinants of EET. Our studies identify these cytochromes as extracellular and reveal potentially novel mechanisms of cell-to-mineral interactions in thermal environments.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

The molecular architecture distinctions between compression, opposite and normal wood of Pinus radiata

In gymnosperms compression wood is a specialised type of structural cell wall formed in response to biomechanical stresses. The differences in terms of gross structure, ultrastructure and chemistry are well-known. However, the differences between compression wood, normal wood, and opposite wood regarding the arrangements and interactions of the various polymers and water within their cell walls still needs to be established. The analysis of 13 C-labelled Pinus radiata by solid-state NMR spectroscopy and other complementary techniques revealed several new aspects of compression and opposite wood molecular architecture. Compared to normal wood, compression wood has a lower water content, its overall nanoporosity is reduced, and the water and matrix polymers have a lower molecular mobility. Galactan, which is a specific marker of compression wood, is broadly distributed within the cell wall, disordered, and not aligned with cellulose, and is found to be in close proximity to xylan. Dehydroabietic acid (a resin acid) is immobilised and close to the H-lignin only in compression wood. Although the overall molecular mobility of normal wood and opposite wood are similar, opposite wood has different arabinose conformations, a large increase in the amount of chain ends, contains significantly more galactan and has additional unassigned mobile components highlighting the different molecular arrangement of cell wall polymers in opposite and normal wood.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Disruption of Z-Disc Function Promotes Mechanical Dysfunction in Human Myocardium: Evidence for a Dual Myofilament Modulatory Role by Alpha-Actinin 2

The ACTN2 gene encodes α-actinin 2, located in the Z-disc of the sarcomeres in striated muscle. In this study, we sought to investigate the effects of an ACTN2 missense variant of unknown significance (p.A868T) on cardiac muscle structure and function. Left ventricular free wall samples were obtained at the time of cardiac transplantation from a heart failure patient with the ACTN2 A868T heterozygous variant. This variant is in the EF 3–4 domain known to interact with titin and α-actinin. At the ultrastructural level, ACTN2 A868T cardiac samples presented small structural changes in cardiomyocytes when compared to healthy donor samples. However, contractile mechanics of permeabilized ACTN2 A868T variant cardiac tissue displayed higher myofilament Ca 2+ sensitivity of isometric force, reduced sinusoidal stiffness, and faster rates of tension redevelopment at all Ca 2+ levels. Small-angle X-ray diffraction indicated increased separation between thick and thin filaments, possibly contributing to changes in muscle kinetics. Molecular dynamics simulations indicated that while the mutation does not significantly impact the structure of α-actinin on its own, it likely alters the conformation associated with titin binding. Our results can be explained by two Z-disc mediated communication pathways: one pathway that involves α-actinin’s interaction with actin, affecting thin filament regulation, and the other pathway that involves α-actinin’s interaction with titin, affecting thick filament activation. This work establishes the role of α-actinin 2 in modulating cross-bridge kinetics and force development in the human myocardium as well as how it can be involved in the development of cardiac disease.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1964

Gravity, radiation and growth.

Biological effect of x-ray irradiation and increased gravity on ultrastructural alteration and growth curve in phage-free escherichia coli b cells

X-RAY IRRADIATION↗
NASA NTRS1973

Special hematologic effects (M115), part E

All routine hematological measurements for the Skylab simulation test were within normal astronaut population limits for the CDR, SPT, and PLT, with one exception: A significant lymphopenia was observed in the PLT during the post test period, possibly the reflection of increased adrenal corticoid secretion. No ultrastructural red cell membrane abnormalities were observed in any of the subjects, nor were any red corpuscle morphological abnormalities noted. Slight elevations in the PLT's red corpuscular potassium were observed in the younger corpuscles after chamber entrance and again upon egress. This probably represents newly released young red cells from hematopoietic tissue. Flame photometric analyses confirm the fact that potassium is indeed higher in the younger cells of all subjects examined.

Kimzey, S. L.↗
NASA NTRS1974

Investigations in space-related molecular biology

Improved instrumentation and preparation techniques for high resolution, high voltage cryo-electron microscopic and diffraction studies on terrestrial and extraterrestrial specimens are reported. Computer correlated ultrastructural and biochemical work on hydrated and dried cell membranes and related biological systems provided information on membrane organization, ice crystal formation and ordered water, RNA virus linked to cancer, lunar rock samples, and organometallic superconducting compounds. Apollo 11, 12, 14, and 15 specimens were analyzed

Fernandez-Moran, H.↗
NASA NTRS1974

Effects of prolonged acceleration with or without clinostat rotation on seedlings of Arabidopsis thaliana (L.) Heynh

Three 21-day tests of the effects of chronic centrifugation were carried out on populations of Arabidopsis thaliana. In addition to 1 g the resultant g-forces tested were: 2,4,6,8,16, and 20 g. Observed end points included gross morphological characters such as size of plant organs and, at the other extreme, features of sub-cellular structure and ultrastructure. Plants were grown on banks of clinostats. The acceleration vector was directed either parallel with the plants' axes or transverse to the axes. Plant responses to chronic axial acceleration and to transverse acceleration with clinostated plants were determined. From the data obtained it was possible in some cases: (1) to determine the g-functions of specific plant developmental characters; (2) to extrapolate those functions to the hypothetical value at zero g in order to predict (tentatively) the morphology of a plant grown in space, (3) to describe morphological effects of clinostat rotation, (4) to determine which of those effects was influenced by the prevailing g-force, and (5) to put to direct test the assumption that clinostat rotation nullifies or compensates for the influence of gravity.

Brown, A. H.↗
NASA NTRS1973

Lipid composition of slash pine tissue cultures grown with lunar and earth soils

Lipid analyses were conducted on slash pine tissues grown in culture in the presence of lunar (Apollo 15) and earth soils. Significant reductions in the total lipids, fatty acids, and sterol components were found in the tissues grown in contact with each of the soils employed when compared to the control. Tissues grown with lunar soil showed the greatest reductions. These results are discussed with respect to previous ultrastructural studies on similarly treated slash pine tissues and lipid analyses on tobacco tissue cultures.

Laseter, J. L.↗
NASA NTRS1973

Applications of cryogenics in electron microscopy

Description of research and development efforts which resulted in a high-voltage cryoelectron microscope system capable of consistent operation at 1.8 to 4.2 K. Attention is given to the design and operation of superconducting objective lenses providing enhanced resolution during longer exposure times at lower beam intensities (thus reducing radiation damage of specimens). A specific system described combines a closed-cycle superfluid helium refrigerator integrated with a modified 200 kV electron microscope. Consistent resolutions of 8 to 16 A are attained with significantly reduced radiation damage, contamination, and thermal noise in prolonged vibration-free examination of specimens at temperatures from 1.8 to 4.2 K. Applications in specific disciplines are discussed, including membrane ultrastructure, cryobiology, microelectronics, and general superconductivity research.

Fernandez-Moran, H.↗
NASA NTRS1974

Cardiac mechanics: Physiological, clinical, and mathematical considerations

Recent studies concerning the basic physiological and biochemical principles underlying cardiac muscle contraction, methods for the assessment of cardiac function in the clinical situation, and mathematical approaches to cardiac mechanics are presented. Some of the topics covered include: cardiac ultrastructure and function in the normal and failing heart, myocardial energetics, clinical applications of angiocardiography, use of echocardiography for evaluating cardiac performance, systolic time intervals in the noninvasive assessment of left ventricular performance in man, evaluation of passive elastic stiffness for the left ventricle and isolated heart muscle, a conceptual model of myocardial infarction and cardiogenic shock, application of Huxley's sliding-filament theory to the mechanics of normal and hypertrophied cardiac muscle, and a rheological modeling of the intact left ventricle. Individual items are announced in this issue.

Mirsky, I.↗
NASA NTRS1975

Structural and cytochemical investigations of the gravity receptor under conditions of relative rest and following exposure to accelerations

When investigating the influence of g-forces on vertebrates, a number of cytochemical and ultrastructural changes are observed: deflection of the stereocilia, change in concentration as well as the localization of a number of chemical biologically active substances, displacement of the mitochondria, their pressure against the membranes, the release into the cytoplasm of the ribosomes of nucleolar RNA, the formation of additional membranes in the cytoplasmatic network, etc. According to preliminary data, it is assumed that similar processes are observed in the gravity receptors of invertebrates as well. It is concluded that gravity receptors in vertebrates and invertebrates are strikingly similar despite different evolutionary paths.

Aronova, M. Z.↗
NASA NTRS1975

The response of single human cells to zero gravity

Twenty separate cultures of Wistar-38 human embryonic lung cells were exposed to a zero-gravity environment on Skylab for periods of time ranging from one to 59 days. Duplicate cultures were run concurrently as ground controls. Ten cultures were fixed on board the satellite during the first 12 days of flight. Growth curves, DNA microspectrophotometry, phase microscopy, and ultrastructural studies of the fixed cells revealed no effects of a zero-gravity environment on the ten cultures. Two cultures were photographed with phase time lapse cinematography during the first 27 days of flight. No differences were found in mitotic index, cell cycle, and migration between the flight and control cells. Eight cultures were returned to earth in an incubated state. Karyotyping and chromosome banding tests show no differences between the flight and control cells.

Montgomery, P. O., Jr.↗
NASA NTRS1977

The response of single human cells to zero-gravity

Microscopic and histochemical evaluations of human embrionic lung cells after exposure to zero-gravity are reported. Growth curves, DNA microspectrophotometry, phase microscopy, and ultrastructural studies of fixed cells revealed no effects on the cultures. Minor unexplained differences have been found in biochemical constituents of the samples.

Montgomery, P. O., Jr.↗
NASA NTRS1977

Further investigation of the spontaneous and evoked activity of the primary neurons of statoreceptors (and other receptors) of the labyrinth of the bullfrog before, during and after an extended period of weightlessness, including alternative intervals of artificial gravity

Vestibular neuron activity was examined by studying nerve stimulation and evoked response. A cooling element, applied to the nerve consisted of a silver hook through which a coolant fluid flowed. Temperature changes were recorded via microtermistors on an eight channel brush recorder, together with response. Diffusion of the cooling effect was measured, recovery time was assessed, and the nerve was then studied hystologically and ultrastructurally. Problems in frog preparation were discussed along with problems in maintaining healthy specimens and bacteria controlled aquaria.

Source record↗
NASA NTRS1978

Response of the iron-deficient erythrocyte in the rat to hyperoxia

Normal and iron-deficient rats were exposed to 90% O2 at 760 Torr for 24 or 48 h. Erythrocyte response to hyperoxia was monitored by potassium (rubidium) influx studies, by storage stress, and by ultrastructural studies. Normal rat erythrocytes exhibited morphological changes and decrease of ouabain-sensitive potassium influx compared to unexposed controls. Both components of erythrocyte potassium influx were affected by iron deficiency. Erythrocytes from unexposed iron-deficient rats showed a 50% increase in ouabain-sensitive potassium influx compared to controls. Iron-deficient rats exposed to hyperoxia for 24 or 48 h, had erythrocytes with morphological changes. Erythrocytes of iron-deficient rats exposed for 24 h showned no influx change; those exposed for 48 h showed a decrease of ouabain-sensitive influx compared to erythrocytes of controls.

Larkin, E. C.↗
NASA NTRS1978

Response of the rat erythrocyte to ozone exposure

Sprague-Dawley rats were exposed to high (6-8 ppm) and moderate (1.5 ppm) amounts of ozone (O3) for various time periods. Response of the rat erythrocyte to ozone was monitored with red blood cell potassium (rubidium) influx studies, with storage stress combined with ultrastructural studies and with levels of erythrocyte glutathione peroxidase and superoxide dismutase. Erythrocytes of rats exposed to O3 showed no significant changes either in their potassium influx or in their glutathione peroxidase and superoxide dismutase activities compared to controls. Erythrocyte differential counts on O3-exposed animals showed significant changes initially as well as following storage stress compared to controls. Rats exposed to 8 ppm O3 for 4 h showed a marked increase in echinocytes. These consistent transformations from discocytes to echinocytes following O3 exposure suggest latent erythrocyte damage has occurred.

Larkin, E. C.↗