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  • 1
    Electronic Resource
    Electronic Resource
    Influence of low temperature preincubation on somatic embryogenesis and ethylene emanation from orchardgrass leaves (1994)
    Springer
    Plant growth regulation 14 (1994), S. 229-234 
    Details
    ISSN: 1573-5087
    Keywords: aminooxyacetic acid ; Dactylis glomerata ; ethylene ; low temperature ; somatic embryogenesis ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objectives of this study were to determine the effects of low temperature (4 °C) preincubation on somatic embryogenesis from orchardgrass (Dactylis glomerata L.) leaf cultures and to relate these effects to ethylene emanation during the preincubation and incubation periods. Experiments were also conducted with an ethylene biosynthesis inhibitor aminooxyacetic acid (AOA). Segments from the innermost two leaves were cultured on SH medium with 30 μM dicamba at 4 °C for 1 to 7 d before transfer to 21 °C. Results from a paired design showed that the embryogenic response of leaf segments preincubated at 4 °C was equal or superior to nonpreincubated leaves at all time periods. Ethylene emanation was decreased during the low temperature incubation. Transfer of leaf segments from 4 °C to 21 °C was accompanied by a burst of ethylene which rose to control levels within 30 min. AOA at 20 and 40 μM decreased ethylene emanation but did not stimulate the embryogenic response. We conclude that the stimulation of somatic embryogenesis by low temperature is probably due to factors other than suppression of ethylene biosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024797
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Distribution of the anionic sites in the cell wall of apple fruit after calcium treatment (1994)
    Springer
    Protoplasma 178 (1994), S. 156-167 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Cationic gold ; Cell wall ; Fruit ; Pectin ; Ripening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ripening and softening of fleshy fruits involves biochemical changes in the cell wall. These changes reduce cell wall strength and lead to cell separation and the formation of intercellular spaces. Calcium, a constituent of the cell wall, plays an important role in interacting with pectic acid polymers to form cross-bridges that influence cell wall strength. In the present study, cationic colloidal gold was used for light and electron microscopic examinations to determine whether the frequency and distribution of anionic binding sites in the walls of parenchyma cells in the apple were influenced by calcium, which was pressure infiltrated into mature fruits. Controls were designed to determine the specificity of this method for in muro labelling of the anionic sites on the pectin polymers. The results indicate that two areas of the cell wall were transformed by the calcium treatment: the primary cell walls on either side of the middle lamella and the middle lamella intersects that delineate the intercellular spaces. The data suggest that calcium ions reduce fruit softening by strengthening the cell walls, thereby preventing cell separation that results in formation of intercellular spaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01545965
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    Paper (German National Licenses)
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  • 3
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    Characterization of atrial natriuretic peptide receptors in brain microvessel endothelial cells (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Atrial natriuretic peptide (ANP) binding and ANP-induced increases in cyclic guanosine monophosphate (cGMP) levels have been observed in brain microvessels (Chabrier et al., 1987; Steardo and Nathanson, 1987), suggesting that this fluid-regulating hormone may play a role in the fluid homeostasis of the brain. This study was initiated to characterize the ANP receptors in primary cultures of brain microvessel endothelial cells (BMECs). The apparent equilibrium dissociation constant, Kd, for ANP increased from 0.25 nM to 2.5 nM, and the number of ANP binding sites as determined by Scatchard analysis increased from 7,100 to 170,000 sites/cell between 2 and 10 days of culture following monolayer formation. Time- and concentration-dependent studies on the stimulation of cGMP levels by ANP indicated that guanylate cyclase-linked ANP receptors were present in BMECs. The relative abilities of ANP, brain natriuretic peptide (BNP), and a truncated analog of ANP containing amino acids 5-27 (ANP 5-27) to modulate the accumulation of cGMP was found to be ANP greater than BNP much greater than ANP 5-27. Affinity cross-linking with disuccinimidyl suberate and radiolabeled ANP followed by gel electrophoresis under reducing conditions demonstrated a single band corresponding to the 60-70 kD receptor, indicating the presence of the nonguanylate cyclase-linked ANP receptor. Radiolabeled ANP binding was examined in the presence of various concentrations of either ANP, BNP, or ANP 5-27 and suggested that a large proportion of the ANP receptors present in blood-brain barrier endothelial cells bind all of these ligands similarly. These data indicate both guanylate cyclase linked and nonguanylate cyclase linked receptors are present on BMECs and that a higher proportion of the nonguanylate cyclase linked receptors is expressed. This in vitro culture system may provide a valuable tool for the examination of ANP receptor expression and function in blood-brain barrier endothelial cells.
    Keywords: Life Sciences (General)
    Type: Journal of cellular physiology (ISSN 0021-9541); Volume 146; 1; 43-51
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    The role of psychoneuroendocrine factors on spaceflight-induced immunological alterations (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper summarizes previous in-flight infections and novel conditions of spaceflight that may suppress immune function. Granulocytosis, monocytosis, and lymphopenia are routinely observed following short duration orbital flights. Subtle changes within the monocyte and T cell populations can also be noted by flow cytometric analysis. The similarity between the immunological changes observed after spaceflight and other diverse environmental stressors suggest that most of these alterations may be neuroendocrine-mediated. Available data support the hypothesis that spaceflight and other environmental stressors modulate normal immune regulation via stress hormones, other than exclusively glucocorticoids. It will be essential to simultaneously collect in-flight endocrine, immunologic, and infectious illness data to determine the clinical significance of these results. Additional research that delineates the neuroendocrine mechanisms of stress-induced changes in normal immune regulation will allow clinicians in the future to initiate prophylactic immunomodulator therapy to restore immune competence altered by the stress of long-duration spaceflight and therefore reduce morbidity from infectious illness, autoimmune disease, or malignancy.
    Keywords: Aerospace Medicine
    Type: Journal of leukocyte biology (ISSN 0741-5400); Volume 54; 3; 236-44
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Influence of low temperature preincubation on somatic embryogenesis and ethylene emanation from orchardgrass leaves (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-16
    Description: The objectives of this study were to determine the effects of low temperature (4 degrees C) preincubation on somatic embryogenesis from orchardgrass (Dactylis glomerata L.) leaf cultures and to relate these effects to ethylene emanation during the preincubation and incubation periods. Experiments were also conducted with an ethylene biosynthesis inhibitor aminooxyacetic acid (AOA). Segments from the innermost two leaves were cultured on SH medium with 30 micromoles dicamba at 4 degrees C for 1 to 7 d before transfer to 21 degrees C. Results from a paired design showed that the embryogenic response of leaf segments preincubated at 4 degrees C was equal or superior to nonpreincubated leaves at all time periods. Ethylene emanation was decreased during the low temperature incubation. Transfer of leaf segments from 4 degrees C to 21 degrees C was accompanied by a burst of ethylene which rose to control levels within 30 min. AOA at 20 and 40 micromoles decreased ethylene emanation but did not stimulate the embryogenic response. We conclude that the stimulation of somatic embryogenesis by low temperature is probably due to factors other than suppression of ethylene biosynthesis.
    Keywords: Life Sciences (General)
    Type: Plant growth regulation (ISSN 0167-6903); 14; 229-34
    Format: text
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    NASA TECHNICAL REPORTS
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