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991.
Neal R. Pellis Thomas J. Goodwin Diana Risin Bradley W. McIntyre Roland P. Pizzini David Cooper Tacey L. Baker Glenn F. Spaulding 《In vitro cellular & developmental biology. Animal》1997,33(5):398-405
Summary Immunity relies on the circulation of lymphocytes through many different tissues including blood vessels, lymphatic channels,
and lymphoid organs. The ability of lymphocytes to traverse the interstitium in both nonlymphoid and lymphoid tissues can
be determined in vitro by assaying their capacity to locomote through Type I collagen. In an attempt to characterize potential causes of microgravity-induced
immunosuppression, we investigated the effects of simulated microgravity on human lymphocyte function in vitro using a specialized rotating-wall vessel culture system developed at the Johnson Space Center. This very low shear culture
system randomizes gravitational vectors and provides an in vitro approximation of microgravity. In the randomized gravity of the rotating-wall vessel culture system, peripheral blood lymphocytes
did not locomote through Type I collagen, whereas static cultures supported normal movement. Although cells remained viable
during the entire culture period, peripheral blood lymphocytes transferred to unit gravity (static culture) after 6 h in the
rotating-wall vessel culture system were slow to recover and locomote into collagen matrix. After 72 h in the rotating-wall
vessel culture system and an additional 72 h in static culture, peripheral blood lymphocytes did not recover their ability
to locomote. Loss of locomotory activity in rotating-wall vessel cultures appears to be related to changes in the activation
state of the lymphocytes and the expression of adhesion molecules. Culture in the rotating-wall vessel system blunted the
ability of peripheral blood lymphocytes to respond to polyclonal activation with phytohemagglutinin. Locomotory response remained
intact when peripheral blood lymphocytes were activated by anti-CD3 antibody and interleukin-2 prior to introduction into
the rotating-wall vessel culture system. Thus, in addition to the systemic stress factors that may affect immunity, isolated
lymphocytes respond to gravitational changes by ceasing locomotion through model interstitium. These in vitro investigations suggest that microgravity induces non-stress-related changes in cell function that may be critical to immunity.
Preliminary analysis of locomotion in true microgravity revealed a substantial inhibition of cellular movement in Type I collagen.
Thus, the rotating-wall vessel culture system provides a model for analyzing the microgravity-induced inhibition of lymphocyte
locomotion and the investigation of the mechanisms related to lymphocyte movement. 相似文献
992.
Cacang Suarna Roger T. Dean Peter T. Southwell-Keeley Douglas E. Moore Roland Stocker 《Free radical research》1997,27(4):397-408
In previous work we demonstrated that up to 30 % of cholesteryl linoleate in homogenates of advanced human plaque samples is present in oxidized forms. Here we show that the material from plaque hexane extracts which co-elutes with cholesteryl hydroxylinoleate on reversed phase HPLC (Anal Biochem 1993;213:79), is composed of several isomers of cholesteryl hydroxy- and cholesteryl oxo-octadecadienoate. Enzymatic hydrolysis and measurement of liberated cholesterol and disappearance of the esters revealed that almost all of the material consisted of unoxidized cholesterol esterified to oxidized derivatives of octadeca-dienoate. Semi-preparative reversed-phase HPLC was used to obtain sufficient quantities of this co-eluting material to undertake normal phase HPLC separation of these components. The nature of such separated and isolated compounds was identified, by co-chromatography with authentic standards, UV spectroscopy and chemical ionization and electron impact mass spectrometry, as cholesteryl hydroxy- and cholesteryl oxo-octadecadienoate. These oxidized fatty acids have been observed previously in plaque, in agreement with our new unambiguous demonstration of their presence as cholesteryl esters. The application of the methods described for the separation of the various forms of oxidized cholesteryl octadecadienoate may aid mechanistic studies of in vitro and in vivo lipoprotein lipid oxidation. 相似文献
993.
Roland Peter 《当今生物学》2004,34(4):220-228
994.
D?rthe M Katschinski Lu Le Susann G Schindler Tim Thomas Anne K Voss Roland H Wenger 《Cellular physiology and biochemistry》2004,14(4-6):351-360
Hypoxia-inducible factor (HIF) alpha subunits are induced under hypoxic conditions, when limited oxygen supply prevents prolyl hydroxylation-dependent binding of the ubiquitin ligase pVHL and subsequent proteasomal degradation. A short normoxic half-life of HIF-alpha and a very rapid hypoxic protein stabilization are crucial to the cellular adaptation to changing oxygen supply. However, the molecular requirements for the unusually rapid mechanisms of protein synthesis, folding and nuclear translocation are not well understood. We and others previously found that the chaperone heat-shock protein 90 (HSP90) can interact with HIF-1alpha in vitro. Here we show that HSP90 also interacts with HIF-2alpha and HIF-3alpha, suggesting a general involvement of HSP90 in HIF-alpha stabilization. The PAS B domain, common to all three alpha subunits, was required for HSP90 interaction. ARNT competed with HSP90 for binding to the PAS B domain since an excess of either component inhibited the activity of the other. HSP90 as well as the heterocomplex members HSP70 and p23, but not HSP40, were detected in immunoprecipitations of endogenous cellular HIF-1alpha. While HSP90 and HSP70 bound to HIF-1alpha predominantly under normoxic conditions, ARNT bound to HIF-1alpha primarily under hypoxic conditions, suggesting that ARNT displaced HSP90 from HIF-1alpha following nuclear translocation. Hypoxic accumulation of HIF-1alpha was delayed in a novel cell model deficient for HSP90beta as well as after treatment of wild-type cells with the HSP90 inhibitor geldanamycin, suggesting that HSP90 activity is involved in the rapid HIF-1alpha protein induction. 相似文献
995.
Roland Wacker Stanka Stoeva Karola Pfüller Uwe Pfüller Wolfgang Voelter 《Journal of peptide science》2004,10(3):138-148
The complete primary structure of the A chain of mistletoe lectin III (ML3A), a type II ribosome-inactivating protein, was determined using proteolytic digests of ML3A, HPLC separation of the peptides, Edman degration and MALDI-MS. Based on our results, ML3A consists of 254 amino acid residues, showing a high homology to the A chain of isolectin ML1 with only 24 amino acid residue exchanges. A striking important structural difference compared with ML1A is the lack of the single N-glycosylation site in ML3A due to an amino acid exchange at position 112 (ML1A: NL112GS ==> ML3A: T112GS). The alignment of ML3A with the A chains of ML1, isoabrins, ricin D, Ricinus communis agglutinin and three lectins, identified from the Korean mistletoe Viscum album ssp. coloratum, demonstrates the rigid conservation of all amino acid residues, responsible for the RNA-N-glycosidase activity as reported for ricin D. In addition, the fully determined primary structure of ML3A will give further information about the biological mechanism of mistletoe lectin therapy. 相似文献
996.
Claudia Ludovici Roland Fr?hlich Karsten Vogtt Bj?rn Mamat Mathias Lübben 《European journal of biochemistry》2002,269(10):2630-2637
We developed the synthesis of the caged oxygen donor (micro-peroxo)(micro-hydroxo)bis[bis(bipyridyl)cobalt(III)] complex (HPBC) as nitrate salt, which has, compared with the perchlorate-form described previously [MacArthur, R., Sucheta, A., Chong, F.F. & Einarsdottir, O. (1995) Proc. Natl Acad. Sci. USA, 92, 8105-8109], greatly enhanced solubility. Now, the quantum efficiency of the photolytical release of dioxygen was determined to be 0.4 per photon at a laser wavelength of 308 nm, which was used to observe biological reactions. The X-ray structure of HPBC has been solved, and the molecular interactions of photochemically generated oxygen with cytochrome oxidase were investigated with optical and FT-IR spectroscopy: it acts as acceptor of electrons transferred from prereduced cytochrome bo(3), the heme-copper oxidase from Escherichia coli. FT-IR spectra revealed typical absorbance difference changes in the carbonyl region of cytochrome bo(3), supported by bandshifts due to solvent isotope exchange and by assignment using site-directed mutants. IR difference spectra of the photooxidation reaction using the caged oxygen compound, and of the photoreduction reaction using the caged electron donor FMN, have inverted shapes. The spectroscopic signals of carboxyl groups are thus equivalent in both reactions: the use of chemically produced oxygen allows the observation of the ongoing molecular changes of cytochrome bo(3) oxidase under quasi-physiological conditions. 相似文献
997.
Gary R Hunter Bradley R Newcomer Roland L Weinsier Daniel L Karapondo D Enette Larson-Meyer Denis R Joanisse Marcas M Bamman 《Journal of applied physiology》2002,93(1):70-76
The purpose of this study was to determine whether muscle metabolic capacity was inversely related to age after adjusting for physical activity in sedentary premenopausal women. Eighty-three women (ages 23-47 yr) had their free-living, activity-related energy expenditure evaluated with doubly labeled water procedures, and room calorimeter determined sleeping energy expenditure. Maximum O(2) uptake and strength were evaluated in all subjects, whereas 31P-magnetic resonance spectroscopy determined metabolic economy during maximal exercise, and muscle biopsy maximal enzyme activity was evaluated in subsets of the sample (48 and 18 subjects, respectively). Age was significantly related to whole body treadmill endurance time (r = -0.32), plantar flexion strength (r = -0.29), maximum O(2) uptake (r = -0.27), (31)P-magnetic resonance spectroscopy ADP recovery rate (r = -0.44), and anaerobic glycolytic capacity (r = -0.37), and muscle biopsy citrate synthase activity (r = -0.48), glyceraldehyde-3-phosphate dehydrogenase (r = -0.54), phosphofructokinase (r = -0.62), and phosphorylase (r = -0.58) activity even after adjusting for activity-related energy expenditure. These data suggest that, in sedentary premenopausal women, both oxidative and glycolytic muscle capacity decrease with age even when physical activity is taken into account. 相似文献
998.
999.
Current alarm systems in intensive care units create a very high rate of false positive alarms because most of them simply compare physiological measurements to fixed thresholds. An improvement can be expected when the actual measurements are replaced by smoothed estimates of the underlying signal. However, classical filtering procedures are not appropriate for signal extraction, as standard assumptions, such as stationarity, do no hold here: the time series measured often show long periods without change, but also upward or downward trends, sudden shifts and numerous large measurement artefacts. Alternative approaches are needed to extract the relevant information from the data, i.e., the underlying signal of the monitored variables and the relevant patterns of change, such as abrupt shifts and trends. This article reviews recent research on filter-based online signal extraction methods designed for application in intensive care. 相似文献
1000.
Birgit Gielen Hans J. De Boeck Catherine M. H. M. Lemmens Roland Valcke Ivan Nijs Reinhart Ceulemans 《Physiologia plantarum》2005,125(1):52-63
Model ecosystems were grown in 12 sunlit, climate-controlled chambers to gain insight into the effects of elevated (+3°C) air temperature (Tair ) on temperate grasslands. In this study, the hypothesis of delayed senescence in response to elevated Tair was tested for Rumex acetosa L. and Plantago lanceolata L. During the autumn of the first treatment year, frequent measurements were made of leaf chlorophyll a (Chl a ) fluorescence transients. Chl fluorescence images of individual leaves as well as digital colour images of these ecosystems were captured. Chl fluorescence variables, such as the maximum quantum yield of primary photochemistry (Fv /Fm ), indicated a decreasing efficiency with time. Despite no treatment effect on Fv /Fm , other variables derived from the Chl fluorescence transients showed a strong trend towards a positive effect of a 3°C temperature increase on the photosynthetic performance of R. acetosa and P. lanceolata in the first year. After mid-September, the initial positive treatment effect disappeared for R. acetosa , strongly suggesting that leaf lifespan of this species was shortened by higher Tair . One possible explanation is more intense drought stress in the elevated compared to the ambient temperature treatments. Second-year measurements were possibly too limited in time to confirm this trend. These results show that temperate grassland species may take advantage of a future increase in Tair during autumn. This will ultimately depend on the species' degree of acclimation to a temperature change and on the resistance to drought stress. 相似文献