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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Ultrastructural changes in rat lung during long-term exposure to oxygen.

The pathogenesis of oxygen toxicity in the lung of rats was studied by electron microscopy. The following long-term effects were established: (1) a progressive destruction of the blood-air barrier beginning with the endothelial cell layer; (2) a profuse edema in the interstitial spaces in the pleural space in the alveoli and in the cytoplasm and organelles; (3) a continuing increase in the quantity and complexity of the alveolar exudate; (4) gradual hemolysis of red blood cells; and (5) eventual subsiding of the interstitial edema in surviving rats with a concomitant development of emphysema.

Harrison, G. A.↗
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 NTRS1974

Ultrastructural response of rat lung to 90 days' exposure to oxygen at 450 mm Hg

Young Sprague-Dawley rats were exposed to 100% oxygen at 450 mm Hg in constant environment capsules for 90 days. Lung tissue examined by electron microscopy revealed a number of changes, many similar to those observed after exposure to oxygen at 760 mm Hg for shorter periods of time. Alterations in vesicle size and number and in mitochondrial matrix and cristae appear in both the endothelial and epithelial cells. Blebbing and rarefication of cytoplasm occur in both cell layers of the alveolo-capillary wall. Also seen are fluid in the basement membrane, platelets in the capillaries, and alveolar fluid and debris. All of these alterations occur at 1 atm exposure. However, after exposure to 450 mm Hg the changes are not as widespread nor as destructive as they are at the higher pressure.

Harrison, G. A.↗
NASA NTRS1977

Ultrastructural changes in tracheal epithelial cells exposed to oxygen

White albino rats were sacrificed after 24, 36, 48, 72, and 96 h of exposure to 100% O2 at 1 atm. Tissue was prepared for the scanning electron microscope (SEM) by Critical Point Drying and for the transmission electron microscope (TEM) by plastic embedding. Scanning microscopy showed a loss of microvilli after 48 h of exposure. Cilia appeared relatively normal with SEM, but TEM revealed changes in the outer membrane. In TEM, nonciliated cells appeared swollen and often encroached on the ciliated cells. A heavy mucous blanket remained even after processing. All the changes observed that are induced by oxygen exposure contribute to mucostasis, reducing and/or halting mucociliary clearance.

Philpott, D. E.↗
NASA NTRS1980

Ultrastructural studies of the mitochondriae in the striated muscles of birds with regard to experimental hypokinesis

Electron microscopic studies were carried out on the mitochrondria of the transversely striated muscles with regard to experimental hypokinesia. As compared to the central group the mitochondria of m. pectoralis thoracicus and the m. iliotibialis posterior in hypokinetic birds reveal marked changes. In filamentous and ovoid mitochondria, vacuoles can be observed which in some cases produced larger light formations with following disappearance of the cristae and destruction of mitochondria. Fat particles located at the poles of the altered mitochondria, sporadically occurring also laterally, presented another finding. The Z-lines of the sarcomere did not form a continuous line, but were somewhat shifted.

Belak, M.↗
NASA NTRS1983

Ultrastructure of meristem and root cap of pea seedlings under spaceflight conditions

Data of electron microscopic analysis of meristem and root cap of pea seedlings grown aboard the Salyut-6 orbital research station in the Oazis apparatus and in the laboratory are presented. The main morphological and anatomical characteristics of the test and control plants are shown to be similar. At the same time, some differences are found in the structural and functional organization of the experimental cells as compared to the controls. They concern first of all the plastic apparatus, mitochondria and Golgi apparatus. It is assumed that cell function for certain periods of weightlessness on the whole ensures execution of the cytodifferentiation programs genetically determined on the Earth. Biochemical and physiological processes vary rather markedly due to lack of initially rigorous determination.

Sytnyk, K. M.↗
NASA NTRS1990

Experiment K-6-13. Morphological and biochemical examination of heart tissue. Part 1: Effects of microgravity on the myocardial fine structure of rats flown on Cosmos 1887. Ultrastructure studies. Part 2: Cellular distribution of cyclic ampdependent protein kinase regulatory subunits in heart muscle of rats flown on Cosmos 1887

The left ventricle of hearts from rats flown on the Cosmos 1887 biosatellite for 12.5 days was compared to the same tissue of synchronous and vivarium control animals maintained in a ground based laboratory. The volume density of the mitochondria in the myocardium of the space-flown animals was statistically less (p equal less than 0.01) than that of the synchronous or vivarium control rats. Exposure to microgravity resulted in a certain degree of myocardial degeneration manifested in mitochondrial changes and accumulation of myeloid bodies. Generalized myofibrillar edema was also observed.

Philpott, D. E.↗
NASA NTRS1990

Sequence of Tissue Responses in the Early Stages of Experimental Allergic Encephalomyelitis (EAE): Immunohistochemical, Light Microscopic, and Ultrastructural Observations in the Spinal Cord

Experimental allergic encephalomyelitis (EAE) was induced in adult Lewis rats with purified guinea pig CNS myelin and Freund's adjuvant. As soon as the very earliest clinical signs appeared the animals were perfused with fixatives and the spinal cord analyzed by electron microscopy, silver methods, and immunocytochemistry. Our findings suggest that in the early stages of EAE a sequence of events can be traced, although these events frequently overlap. The earliest morphological change appears to be astrocytic edema in both the cell body and processes. Increased amounts of glycogen particles and dispersion of glial filaments are prominent. These changes seem to occur just prior to the time when inflammatory cells begin to penetrate the capillary walls. Invasion of the neuropil mainly by macrophages and lymphocytes closely follows. Both macrophages and microglia seem to participate in phagocytosis of oligodendrocytes and myelin. Demyelination, however, is not a prominent feature at this early stage.

DAmelio, Fernando E.↗
NASA NTRS2001

Chloroplast Ultrastructure of the Alga Phaeocystis antarctica Karsten: A New Structural Model Using Electron Tomography

Understanding the light-harvesting properties of algae and higher plants are a fundamental topic in photosynthesis research. Using thick sections obtained from fixed and embedded cultures of colonial P antarctica, we calculate tomographic reconstructions of individual chloroplasts under light-limiting and saturating conditions for net photosynthesis. Our goal is to gain an understanding of the continuity of thylakoid membranes and understand the spatial relationship between the pyrenoid, the starch containing organelle, and thylakoid membranes. We found that Phaeocystis showed considerable morphological and physiological flexibility in response to environmental light levels. We found that the thylakoids generally run parallel to the chloroplast membrane with many junctures and bifurcations, many of which are in contact with the chloroplast membrane itself. The considerable flexibility in the. thylakoid membranes allows for the accommodation of the pyrenoid structure. The arrangement of the thylakoids within these structures resemble those found in new structures of mitochondria cristae. We present a new structural model for algal chloroplasts which greatly revises current concepts of thylakoid membrane structure in relation to photoacclimation.

Moisan, Tiffany A.↗
NASA NTRS2001

The interaction of microgravity and ethylene on the ultrastructure cell and Ca2+ localization in soybean hook hypocotyl

Calcium ions are secondary messenger in numerous cellular processes of plant grown at 1 g. Ca2+ are connected with oxygen atoms, of pectin carboxy groups and/or with H(+)-groups of protein (Roux and Slocum, 1982; Hepler and Wayne, 1985). The influence of altered gravity on the calcium balance in some cells is established. The increased synthesis of ethylene in plant grown in microgravity caused the change of the structural-functional organization of cell (Hensel and Iversen, 1980; Hilaire et al., 1996). Available data put the new question: how do high ethylene level and microgravity influence on the redistribution of Ca2+ in cell of seedling in early stage of growth? Therefore, the goal of our data was the comparable study of the cell ulltrastructure and localization of Ca2+ in hook hypocotyl of soybean seedling under interaction of microgravity and ethylene.

STS-87 Shuttle Project↗
NASA NTRS2000

Ultrastructural analyses of somatic embryo initiation, development and polarity establishment from mesophyll cells of Dactylis glomerata

Somatic embryos initiate and develop directly from single mesophyll cells in in vitro-cultured leaf segments of orchardgrass (Dactylis glomerata L.). Embryogenic cells establish themselves in the predivision stage by formation of thicker cell walls and dense cytoplasm. Electron microscopy observations for embryos ranging from the pre-cell-division stage to 20-cell proembryos confirm previous light microscopy studies showing a single cell origin. They also confirm that the first division is predominantly periclinal and that this division plane is important in establishing embryo polarity and in determining the embryo axis. If the first division is anticlinal or if divisions are in random planes after the first division, divisions may not continue to produce an embryo. This result may produce an embryogenic cell mass, callus formation, or no structure at all. Grant numbers: NAGW-3141, NAG10-0221.

Non-NASA Center↗
NASA NTRS1997

A regional ultrastructural analysis of the cellular and synaptic architecture in the chinchilla cristae ampullares

The chinchilla crista ampullaris was studied in 10 samples, each containing 32 consecutive ultrathin sections of the entire neuroepithelium. Dissector methods were used to estimate the incidence of various synaptic features, and results were confirmed in completely reconstructed hair cells. There are large regional variations in cellular and synaptic architecture. Type I and type II hair cells are shorter, broader, and less densely packed in the central zone than in the intermediate and peripheral zones. Complex calyx endings are most common centrally. On average, there are 15-20 ribbon synapses and 25-30 calyceal invaginations in each type I hair cell. Synapses and invaginations are most numerous centrally. Central type II hair cells receive considerably fewer afferent boutons than do peripheral type II hair cells, but have similar numbers of ribbon synapses. The numbers are similar because central type II hair cells make more synapses with the outer faces of calyx endings and with individual afferent boutons. Most afferent boutons get one ribbon synapse. Boutons without ribbon synapses were only found peripherally, and boutons getting multiple synapses were most frequent centrally. Throughout the neuroepithelium, there is an average of three to four efferent boutons on each type II hair cell and calyx ending. Reciprocal synapses are rare. Most synaptic ribbons in type I hair cells are spherules; those in type II hair cells can be spherical or elongated and are particularly heterogeneous centrally. Consistent with the proposal that the crista is concentrically organized, the intermediate and peripheral zones are each similar in their cellular and synaptic architecture near the base and near the planum. An especially differentiated subzone may exist in the middle of the central zone.

Non-NASA Center↗