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排序方式: 共有544条查询结果,搜索用时 15 毫秒
31.
Augurelle AS Penta M White O Thonnard JL 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》2002,9(1):P51-P53
The objective of this study was to measure the forces applied on an object manipulated in different gravitational fields attained during parabolic flights. Eight subjects participated flights (ES) and four were inexperienced (NES). They had to move continuously an instrumented object up and down in three different gravitational conditions (1 g, 1.8 g, 0 g). In 1 g, the grip force precisely anticipated the fluctuations of load force which was maximum and minimum at the bottom and at the top of the arm trajectory respectively. When the gravity changed (0 g and 1.8 g), the grip-load force coupling persisted for all the subjects from the first parabola. While the ES immediately exerted a grip force appropriate to the gravity, the NES dramatically increased their grip when faced with hyper and microgravity for the first time. Then, they progressively released their grip until a continuous grip-load force relationship with regard to 1 g was established after the fifth parabola. We suggest that each new gravitational field is rapidly incorporated into an internal model within the CNS which can then be reused as required by the occasion. 相似文献
32.
Charpenel C Guillon AS Dorson O Boucly C Mathieu B Montagnon M Merlet F Van Amerongen G Bisson JP de Mazancourt P 《Genetic testing》2002,6(3):207-210
Sixteen sequence-tagged sites (STSs) were combined in five amplification reactions, to screen for deletions of DNA fragments located within the AZFa, AZFb, and AZFc regions of the Y chromosome. This multiplex strategy is fast and reliable, and most of the azoospermia-associated deletions reported so far are detected with this simplified method. Internal control STSs are included that allow discrimination between deletion and failure of amplification. 相似文献
33.
Dournon C Membre H Brohm PE Coince A Cornu N Dreyer L Florentin J Jeanneau L Henniquin C Houbre M Guerard M Lecomte N Maxant L Schluraff M Venandet AS Jusyte A Simmet D Bocking D Flaig D Santak L Bolek S Goppel V Rossignon JP Trossat MA Raux M Forster S Staudenmaier G Boser S Horn E 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》2002,9(1):P375-P376
The German-French biological experiment AQUARIUS-XENOPUS which flew on the Soyuz flight Andromede to the International Space Station ISS (launched October 21, 2001 in Baikonour/Kazakhstan) was extended by an outreach project. Pupils of class 10 to 12 from Ulm/D and Nancy-Tomblaine/F studied swimming behavior of Xenopus tadpoles on ground. They were instructed to perform all experimental steps following the protocol of similar video recordings on ISS. After the flight, they evaluated the kinetics of swimming of both ground controls and space animals. The pupil project included theoretical components to introduce them to the field of gravitational biology. One feature of the project was the exchange of ideas between pupils by meetings which took place in Ulm (June 2001), Nancy (February 2002) and Paris (May 2002). We consider our approach as a successful way to include young people in space experiments on a cheap cost level and to bring ideas of gravitational biology into the curricula of European schools. 相似文献
34.
Two clusters of charged residues located in the electropositive face of the von Willebrand factor A1 domain are essential for heparin binding 总被引:1,自引:0,他引:1
Rastegar-Lari G Villoutreix BO Ribba AS Legendre P Meyer D Baruch D 《Biochemistry》2002,41(21):6668-6678
The VWF A1 domain seems to possess two heparin binding regions (residues 565-587 and 633-648) displaying positively charged amino acids, but the overall polyanion-A1 domain interaction scheme remains essentially elusive. To probe this molecular reaction as well as the role of electrostatic forces in VWF-heparin interaction, we performed mutagenesis and molecular modeling experiments. Fifteen mutated rVWFs were expressed [R571A, K572A, R573A, K585A, R571A/K572A/R573A, R578A/R579A, R578A/R579A/K585A, R571A/K572A/R573A/R578A/R579A/K585A (6A), K642G, K643G, K644G, K645G, K642G/K645G, K643G/K644G, and K642G/K643G/K644G/K645G (4G)]. Experimental results indicate that the multimeric structure of the mutants was similar to that of wild-type (WT) rVWF and that all rVWFs displayed normal binding to four conformation-dependent mAbs directed against the A1 domain. Three variants displayed significant reductions in the level of heparin binding. The 6A variant showed 39.2 +/- 1.3% of the WT rVWF level (p < 0.005), while mutants K643G/K644G and 4G showed 63.6 +/- 3.2 and 53.3 +/- 5% of the WT rVWF level, respectively (p < 0.005). Computational investigations showed that one face of the A1 domain is strongly electropositive, indicating that electrostatic forces should be essential in steering heparin onto its binding site. In agreement with our experimental data, the most striking alterations of the electrostatic potential contours were seen for mutants 4G, K643G/K644G, and 6A. Our data suggest that two clusters, one at positions 571-573, 578, 579, and 585 and the other at positions 642-645, act in concert for the recognition of heparin, forming a single extended binding surface across the electropositive face of the VWF A1 domain. A structural model of the VWF A1 domain-heparin complex is proposed, taking into account both experimental and computer modeling data. 相似文献
35.
Malham SK Lacoste A Gélébart F Cueff A Poulet SA 《Journal of experimental zoology. Part A, Comparative experimental biology》2003,295(2):136-144
Stress is thought to cause increased disease outbreaks and mortality in a number of invertebrates but currently very little information is available on mechanisms linking physiological states of stress and reduced disease resistance in these organisms. In the present study, we examined the possibility that stress alters immune functions, the principal line of defense against pathogens, in a molluscan model, the abalone Haliotis turbeculata. Immune parameters were investigated in abalones subjected to a 15 min mechanical disturbance which, as indicated by noradrenaline and dopamine hemolymphatic levels, resulted in a transient state of physiological stress. During the application of the stressor, immune parameters such as the number of circulating hemocytes, the migratory activity, the phagocytic capacity and the respiratory burst responses of hemocytes, decreased significantly. All parameters returned to initial values within 15-30 min after the end of the disturbance and a transient period of immunostimulation occurred between 100 and 480 min after the stress for all immune parameters except intracellular superoxide anion production. These results indicate that in the abalone H. tuberculata, as in vertebrates, a link exists between stress and the immune system. This may begin to answer why stress and disease outbreaks are linked in shellfish. 相似文献
36.
Goldstein DJ Fondrat C Muri F Nuel G Saragueta P Tocquet AS Prum B 《Comptes rendus biologies》2003,326(3):339-348
Inversions of short genomic sequences play a central role in the generation of protein complexity. More than half of the 1300 motifs registered in ProSite have protein inverse complementary sequences (princoms) among proteins registered in SwissProt. The observed number of princoms occurrences exceeds by far the expected number (p < 10(-10)). Princoms often endow their host proteins with a whole new range of biochemical and physiological capabilities, including the possibility of intramolecular and intermolecular disulfide bond formation. These results support the idea that, like the duplications, the inversions of small genomic fragments have been a fundamental mechanism for shaping genomes. 相似文献
37.
Brevet V Berthiau AS Civitelli L Donini P Schramke V Géli V Ascenzioni F Gilson E 《The EMBO journal》2003,22(7):1697-1706
The number of telomeric DNA repeats at chromosome ends is maintained around a mean value by a dynamic balance between elongation and shortening. In particular, proteins binding along the duplex part of telomeric DNA set the number of repeats by progressively limiting telomere growth. The paradigm of this counting mechanism is the Rap1 protein in Saccharomyces cerevisiae. We demonstrate here that a Rap1-independent mechanism regulates the number of yeast telomeric repeats (TG(1-3)) and of vertebrate repeats (T(2)AG(3)) when TEL1, a yeast ortholog of the human gene encoding the ATM kinase, is inactivated. In addition, we show that a T(2)AG(3)-only telomere can be formed and maintained in humanized yeast cells carrying a template mutation of the gene encoding the telomerase RNA, which leads to the synthesis of vertebrate instead of yeast repeats. Genetic and biochemical evidences indicate that this telomere is regulated in a Rap1-independent manner, both in TEL1 and in tel1Delta humanized yeast cells. Altogether, these findings shed light on multiple repeat-counting mechanisms, which may share critical features between lower and higher eukaryotes. 相似文献
38.
Identification of two human nuclear proteins that recognise the cytosine-rich strand of human telomeres in vitro 总被引:4,自引:2,他引:2
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Lacroix L Liénard H Labourier E Djavaheri-Mergny M Lacoste J Leffers H Tazi J Hélène C Mergny JL 《Nucleic acids research》2000,28(7):1564-1575
Most studies on the structure of DNA in telomeres have been dedicated to the double-stranded region or the guanosine-rich strand and consequently little is known about the factors that may bind to the telomere cytosine-rich (C-rich) strand. This led us to investigate whether proteins exist that can recognise C-rich sequences. We have isolated several nuclear factors from human cell extracts that specifically bind the C-rich strand of vertebrate telomeres [namely a d(CCCTAA)n repeat] with high affinity and bind double-stranded telomeric DNA with a 100× reduced affinity. A biochemical assay allowed us to characterise four proteins of apparent molecular weights 66–64, 45 and 35 kDa, respectively. To identify these polypeptides we screened a λgt11-based cDNA expression library, obtained from human HeLa cells using a radiolabelled telomeric oligonucleotide as a probe. Two clones were purified and sequenced: the first corresponded to the hnRNP K protein and the second to the ASF/SF2 splicing factor. Confirmation of the screening results was obtained with recombinant proteins, both of which bind to the human telomeric C-rich strand in vitro. 相似文献
39.
Direct somatic embryogenesis was induced in root tissues of the Cichorium hybrid `474' (C. intybus L. var. sativum×C. endivia L. var. latifolia). Addition of β-d-glucosyl Yariv reagent (βGlcY), a synthetic phenylglycoside that specifically binds arabinogalactan-proteins (AGPs), to the
culture medium blocked somatic embryogenesis in a concentration-dependent manner with complete inhibition of induction occurring
at 250 μM βGlcY. The AGP-unreactive α-d-galactosyl Yariv reagent had no biological activity in this system. Upon transfer of 250 μM βGlcY-treated roots to control
conditions, somatic embryogenesis was recovered with a time course similar to that of control roots. The βGlcY penetrated
roots and bound abundantly to developing somatic embryos, to the root epidermis and the stele. Immunofluorescence and immunogold
labelling using monoclonal antibodies (JIM13, JIM16 and LM2) revealed that AGPs were localised in the outer cell walls peripheral
cells of the globular embryo. A spatio-temporal expression of AGPs appeared to be associated with differentiation events in
the somatic embryo during the transition from the globular stage to the torpedo stage. To verify βGlcY specificity, molecules
that bound βGlcY were extracted from treated conditioned medium and identified as AGPs by using the same monoclonal antibodies.
In addition, AGPs were found to be abundantly present in the medium during embryogenic culture. All of these results establish
the implication of AGPs in embryo development, and their putative role in somatic embryogenesis is discussed.
Received: 26 August 1999 / Accepted: 28 January 2000 相似文献
40.
Vassili Valayannopoulos Coralie Haudry Valérie Serre Magalie Barth Nathalie Boddaert Jean-Baptiste Arnoux Valérie Cormier-Daire Marlène Rio Daniel Rabier Anne Vassault Arnold Munnich Jean-Paul Bonnefont Pascale de Lonlay Agnès Rötig Anne-Sophie Lebre 《Mitochondrion》2010,10(4):335-341
Deficiencies in two subunits of the succinyl-coenzyme A synthetase (SCS) have been involved in patients with encephalomyopathy and mild methylmalonic aciduria (MMA). In this study, we described three new SUCLG1 patients and performed a meta-analysis of the literature. Our report enlarges the phenotypic spectrum of SUCLG1 mutations and confirms that a characteristic metabolic profile (presence of MMA and C4-DC carnitine in urines) and basal ganglia MRI lesions are the hallmarks of SCS defects. As mitochondrial DNA depletion in muscle is not a constant finding in SUCLG1 patients, this may suggest that diagnosis should not be based on it, but also that alternative physiopathological mechanisms may be considered to explain the combined respiratory chain deficiency observed in SCS patients. 相似文献