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101.
Mame?Oureye SyEmail author Maurice?Sagna Sire?Diedhiou Claudine?Franche Florence?Auguy Emile?Duhoux 《In vitro cellular & developmental biology. Plant》2003,39(5):545-550
Summary The purpose of this study was to establish an efficient in vitro nodulation device for producing actinorhizal root nodules on Allocasuarina verticillata and Casuarina glauca. Seeds from the two species were germinated aseptically and seedlings with at least two photosynthetic branchlets and a 3–5
cm long root system were transferred into Petri dishes containing a biphasic (solid/liquid) medium. To assess the nodulation
capacity, four different culture media were tested. As soon as the root system developed and spread adequately on the surface
of the medium, plants were deprived of nitrogen for at least 1 wk and inoculated with the Frankia strain. The time course nodulation for A. verticillata showed that the basal Hoagland medium supplemented with CaCO3 and KNO3 was most efficient, with 83% of plantlets forming nodules, while the medium supplemented with CaCO3 reached 100% nodulation for C. glauca. This procedure can provide a valuable tool for the study of early events of actinorhizal nodulation and spatio-temporal
expression of symbiotic genes in transgenic Casuarinaceae. 相似文献
102.
103.
Flicker S Vrtala S Steinberger P Vangelista L Bufe A Petersen A Ghannadan M Sperr WR Valent P Norderhaug L Bohle B Stockinger H Suphioglu C Ong EK Kraft D Valenta R 《Journal of immunology (Baltimore, Md. : 1950)》2000,165(7):3849-3859
Almost 90% of grass pollen-allergic patients are sensitized against group 5 grass pollen allergens. We isolated a monoclonal human IgE Fab out of a combinatorial library prepared from lymphocytes of a grass pollen-allergic patient and studied its interaction with group 5 allergens. The IgE Fab cross-reacted with group 5A isoallergens from several grass and corn species. By allergen gene fragmentation we mapped the binding site of the IgE Fab to a 11.2-kDa N-terminal fragment of the major timothy grass pollen allergen Phl p 5A. The IgE Fab-defined Phl p 5A fragment was expressed in Escherichia coli and purified to homogeneity. Circular dichroism analysis revealed that the rPhl p 5A domain, as well as complete rPhl p 5A, assumed a folded conformation consisting predominantly of an alpha helical secondary structure, and exhibited a remarkable refolding capacity. It reacted with serum IgE from 76% of grass pollen-allergic patients and revealed an extremely high allergenic activity in basophil histamine release as well as skin test experiments. Thus, the rPhl p 5A domain represents an important allergen domain containing several IgE epitopes in a configuration optimal for efficient effector cell activation. We suggest the rPhl p 5A fragment and the corresponding IgE Fab as paradigmatic tools to explore the structural requirements for highly efficient effector cell activation and, perhaps later, for the development of generally applicable allergen-specific therapy strategies. 相似文献
104.
Characterisation of the newly identified human Ump1 homologue POMP and analysis of LMP7(beta 5i) incorporation into 20 S proteasomes 总被引:1,自引:0,他引:1
Witt E Zantopf D Schmidt M Kraft R Kloetzel PM Krüger E 《Journal of molecular biology》2000,301(1):1-9
Biogenesis of mammalian 20 S proteasomes occurs via precursor complexes containing alpha and unprocessed beta subunits. A human homologue of the yeast proteasome maturation factor Ump1 was identified in 2D gels of 16 S precursor preparations and designated as POMP (proteasome maturation protein). We show that POMP is detected only in precursor fractions and not in fractions containing mature 20 S proteasome. Northern blot experiments revealed that expression of POMP is induced after treatment with interferon gamma. To analyse the role of the beta 5 propeptide for proper maturation and incorporation of the beta 5 subunit into the complex, human T2 cells, which highly express derivatives of the beta 5i subunit (LMP7), were studied. In contrast to yeast, the presence of the beta 5 propeptide is not essential for incorporation of LMP7 into the proteasome complex. Mutated LMP7 subunits either carrying the prosequence of beta 2i (LMP2) or containing a mutation in the active threonine site are incorporated like wild-type LMP7, while a LMP7 derivative lacking the prosequence completely is incorporated to a lesser extent. Although the absence of the prosequence does not affect incorporation of LMP7, its deletion leads to delayed proteasome maturation and thereby to an accumulation of precursor complexes. As a result of the precursor accumulation, an increased amount of the POMP protein can be detected in these cells. 相似文献
105.
Palmer S Campen CA Allan GF Rybczynski P Haynes-Johnson D Hutchins A Kraft P Kiddoe M Lai M Lombardi E Pedersen P Hodgen G Combs DW 《The Journal of steroid biochemistry and molecular biology》2000,75(1):33-42
We have characterized a series of nonsteroidal progesterone receptor ligands, the tetrahydropyridazines. Compounds in this series, exemplified by RWJ 26819, demonstrate high affinity and unprecedented specificity for the progesterone receptor relative to other steroid hormone receptors. Like steroidal progestins, RWJ 26819 induces binding of the receptor to a progesterone response element in vitro, and stimulates gene expression in and proliferation of T47D human breast cancer cells. When administered to rabbits orally or subcutaneously, the compound induces histological changes in the uterine lining comparable to those induced by levonorgestrel. It also inhibits ovulation in monkeys. Though less potent in cells and in animal models than would be predicted from binding affinity alone, their enhanced selectivity suggests that they could be effectively used in a clinical setting. Most of the tetrahydropyridazines synthesized are progestin agonists or mixed agonists and antagonists in vitro; however, one compound with antagonist activity in the rabbit uterine transformation assay has been identified. 相似文献
106.
107.
In order to study gravity effects on plant structure and function, it may become necessary to remove the g-stimulus. On Earth, various instruments such as clinostats have been used by biologists in an attempt to neutralize the effects
of gravity. In this study, the position of amyloplasts was assayed in columella cells in the roots of Arabidopsisthaliana (L.) Heynh. seedlings grown in the following conditions: on Earth, on a two-dimensional clinostat at 1 rpm, on a three-dimensional
clinostat (also called a random-positioning machine, or an RPM), and in space (true microgravity). In addition, the effects
of these gravity treatments on columella cell area and plastid area also were measured. In terms of the parameters measured,
only amyloplast position was affected by the gravity treatments. Plastid position was not significantly different between
spaceflight and RPM conditions but was significantly different between spaceflight and the classical two-dimensional clinostat
treatments. Flanking columella cells showed a greater susceptibility to changes in gravity compared to the central columella
cells. In addition, columella cells of seedlings that were grown on the RPM did not exhibit deleterious effects in terms of
their ultrastructure as has been reported previously for seedlings grown on a two-dimensional clinostat. This study supports
the hypothesis that the RPM provides a useful simulation of weightlessness.
Received: 5 January 2000 / Accepted: 22 February 2000 相似文献
108.
Irene Mittermann Jacquelyn S. Fetrow Diana L. Schaak Steven C. Almo Dietrich Kraft Erwin Heberle-Bors R. Valenta 《Sexual plant reproduction》1998,11(4):183-191
Profilins are structurally well conserved low molecular weight (12–15 kDa) eukaryotic proteins which interact with a variety
of physiological ligands: (1) cytoskeletal components, e.g., actin; (2) polyphosphoinositides, e.g., phosphatidylinositol-4,5-bisphosphate;
(3) proline-rich proteins, e.g., formin homology proteins and vasodilatator-stimulated phosphoprotein. Profilins may thus
link the microfilament system with signal transduction pathways. Plant profilins have recently been shown to be highly crossreactive
allergens which bind to IgE antibodies of allergic patients and thus cause symptoms of type I allergy. We expressed and purified
from Escherichia coli profilins from birch pollen (Betula verrucosa), humans (Homo sapiens) and yeast (Schizosaccharomyces pombe) and demonstrated that each of these profilins is able to form stable homo- and heteropolymers via disulphide bonds in vitro.
Circular dichroism analysis of oxidized (polymeric) and reduced (monomeric) birch pollen profilin indicates that the two states
have similar secondary structures. Using 125I-labeled birch pollen, yeast and human profilin in overlay experiments, we showed that disulphide bond formation between
profilins can be disrupted under reducing conditions, while reduced as well as oxidized profilin states bind to actin and
profilin-specific antibodies. Exposure of profilin to oxidizing conditions, such as when pollen profilins are liberated on
the surface of the mucosa of atopic patients, may lead to profilin polymerization and thus contribute to the sensitization
capacity of profilin as an allergen.
Received: 25 February 1998 / Revision accepted: 12 May 1998 相似文献
109.
110.