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21.
Xenopus myogenesis is characterized by specific features, different from those of mammalian and avian systems both at the cellular level and in gene expression patterns. During early embryogenesis, after the initial molecular signals inducing mesoderm, the myogenic determination factors XMyoD and XMyf-5 are activated in presomitic mesoderm in response to mesoderm-inducing factors. After these first inductions of the myogenic program, forming muscles in Xenopus can have different destinies, some of these resulting in cell death before adulthood. In particular, it is quite characteristic of this species that, during metamorphosis, the primary myotomal myofibers completely die and are progressively replaced by secondary "adult" multinucleated myofibers. This feature offers the unique opportunity to totally separate the molecular analysis of these two distinct types of myogenesis. The aim of this review is to summarize our knowledge on the cellular and molecular events as well as the epigenetic regulations involved in the construction of Xenopus muscles during development. 相似文献
22.
Serge Perrot Vincent Calvez Jean-Paul Escande Nicolas Dupin Anne-Geneviève Marcelin 《Journal of clinical virology》2003,28(2):165-168
BACKGROUND: Sj?gren's syndrome (SS) is an autoimmune exocrinopathy associated with multiple autoantibodies, lymphocyte infiltration of various organs, and functional deficiency of T cells. Several viruses have been implicated by PCR based studies, but their contribution to the pathophysiology of SS is still controversial. OBJECTIVES: In an attempt to explore the presence of human herpesviruses DNA sequences in salivary glands biopsies from patients suffering of SS, a recently developed strategy based on PCR with consensus degenerated primers that allowed to detect known and eventually unknown herpesviruses was used. STUDY DESIGN: Salivary glands biopsies from 55 patients suffering of primary and SS syndrome were explored by herpesviruses consensus PCR primers and all the PCR products were sequenced. RESULTS: Nine out of 55 salivary glands were positive by PCR and sequence analyses allowed to identify Epstein-Barr virus (EBV) in 6 cases and herpes simplex virus (HSV)-1 in 3 cases. We did not detect any sequences that could be related to a new herpesvirus. CONCLUSION: In view of the good sensitivity of the technique used, our study is not consistent with SS being associated with an unknown herpesvirus. However, our results suggest that EBV and HSV-1 could be implicated in a subset of SS cases and this possibility needs to be explored, to assess the potential benefit of antiviral drugs in some cases. 相似文献
23.
Lapaix F Egée S Gibert L Decherf G Thomas SL 《Pflügers Archiv : European journal of physiology》2002,445(1):152-160
The patch-clamp technique was used to demonstrate the presence of ATP-sensitive K(+) channels and Ca(2+)-activated K(+) channels in lamprey ( Petromyzon marinus) red blood cell membrane. Whole-cell experiments indicated that the membrane current under isosmotic (285 mosmol l(-1)) conditions is carried by K(+). In the inside-out configuration an ATP-sensitive K(+) channel (70-80 pS inward, 35-40 pS outward) was present in 35% of patches. Application of ATP to the intracellular side reduced unitary current with half-maximal inhibition in the range 10-100 microM. A block was obtained with 100 microM lidocaine and inhibition was obtained with 0.5 mM barium acetate. A Ca(2+)-activated K(+) channel (25-30 pS inward, 10-15 pS outward) was present in 57% of patches. Inhibition was produced by 10 mM TEA and 500 nM apamin and sensitivity to Ba(2+) was lower than for ATP-sensitive channels. No spontaneous channel activity was recorded in the cell-attached configuration under isotonic conditions. With hypotonic saline 68% of patches showed spontaneous single-channel activity, and, of 75 active patches, 66 cell-attached patches showed channel activity corresponding to Ca(2+)-activated K(+) channels. 相似文献
24.
Eucaryotic Expression of the Nucleocapsid Protein Gene of Porcine Circovirus Type 2 and Use of the Protein in an Indirect Immunofluorescence Assay for Serological Diagnosis of Postweaning Multisystemic Wasting Syndrome in Pigs 下载免费PDF全文
Sbastien Racine Ali Kheyar Carl A. Gagnon Benoît Charbonneau Serge Dea 《Clinical and Vaccine Immunology : CVI》2004,11(4):736-741
The purpose of this study was to develop a sensitive, rapid, and inexpensive immunofluorescence assay (IFA) using a recombinant porcine circovirus type 2 (PCV2) nucleocapsid protein for the serological detection of PCV2-specific antibodies in pig sera. The viral nucleocapsid protein encoded by the PCV2 ORF2 gene has recently been identified as the most immunoreactive viral protein that carries type-specific antigenic determinants. The ORF2 sequence of the IAF-2897 strain of PCV2 has been cloned into a pCEP5 eucaryotic expression vector under the control of the cytomegalovirus promoter, downstream of a polyhistidine sequence tag. The recombinant plasmid was used in transfection experiments with human epithelial kidney 293 cells that were further tested, and positive expression of the viral nucleocapsid protein was confirmed by IFA and Western blotting. Strong, specific fluorescence was observed in the nuclei of transfected cells. Test specificity to PCV2 was verified with several related infectious agents. Sensitivity was compared to that of standard IFA using PCV2-infected cells by evaluating the reactivities of 44 field serum samples from pigs on farms with a porcine population suffering from postweaning multisystemic wasting syndrome. The recombinant nucleocapsid-based test was able to detect 15 more positive-testing pigs than the PCV2-based IFA. Therefore, the relative sensitivity of the latter test was estimated at only 57.1% compared to that of the recombinant nucleocapsid-based test. The recombinant fusion protein has been purified by affinity chromatography and is being used to develop further sensitive serological tests. 相似文献
25.
Changes in blood lactate and respiratory gas exchange measures in sports with discontinuous load profiles 总被引:2,自引:0,他引:2
Smekal G von Duvillard SP Pokan R Tschan H Baron R Hofmann P Wonisch M Bachl N 《European journal of applied physiology》2003,89(5):489-495
This study compares two different sport events (orienteering = OTC; tennis = TEC) with discontinuous load profiles and different
activity/recovery patterns by means of blood lactate (LA), heart rate (HR), and respiratory gas exchange measures (RGME) determined
via a portable respiratory system. During the TEC, 20 tennis-ranked male subjects [age: 26.0 (3.7) years; height: 181.0 (5.7) cm;
weight: 73.2 (6.8) kg; maximal oxygen consumption (V˙O2max): 57.3 (5.1) ml·kg−1·min−1] played ten matches of 50 min. During the OTC, 11 male members of the Austrian National Team [age: 23.5 (3.9) years; height:
183.6 (6.8) cm; weight: 72.4 (3.9) kg; V˙O2max: 67.9 (3.8) ml·kg−1·min−1] performed a simulated OTC (six sections; average length: 10.090 m). In both studies data from the maximal treadmill tests
(TT) were used as reference values for the comparison of energy expenditure of OTC and TEC. During TEC, the average V˙O2 was considerably lower [29.1 (5.6) ml·kg−1·min−1] or 51.1 (10.9)% of VO2max and 64.8.0 (13.3)% of V˙O2 determined at the individual anaerobic threshold (IAT) on the TT. The short high-intensity periods (activity/recovery = 1/6)
did not result in higher LA levels [average LA of games: 2.07 (0.9) mmol·l−1]. The highest average V˙O2 value for a whole game was 47.8 ml·kg−1·min−1 and may provide a reference for energy demands required to sustain high-intensity periods of tennis predominately via aerobic
mechanism of energy delivery. During OTC, we found an average V˙O2 of 56.4 (4.5) ml·kg−1·min−1 or 83.0 (3.8)% of V˙O2max and 94.6 (5.2)% of V˙O2 at IAT. In contrast to TEC, LA were relatively high [5.16 (1.5) mmol·l−1) although the average V˙O2 was significantly lower than V˙O2 at IAT. Our data suggest that portable RGEM provides valuable information concerning the energy expenditure in sports that
cannot be interpreted from LA or HR measures alone. Portable RGEM systems provide valuable assessment of under- or over-estimation
of requirements of sports and assist in the optimization and interpretation of training in athletes.
Electronic Publication 相似文献
26.
27.
HGT1 encodes a high-affinity glutathione transporter in the yeast Saccharomyces cerevisiae that is induced under sulphur limitation. The present work demonstrates that repression by organic sulphur sources is under the control of the classic sulphur regulatory network, as seen by the absence of expression in a met4 background. Cysteine appeared to be the principal regulatory molecule, since elevated levels were seen in str4 strains (deficient in cysteine biosynthesis) that could be repressed by elevated levels of cysteine, but not by methionine or glutathione. Investigations into cis-regulatory elements revealed that the previously described motif, a 9-bp cis element, CCGCCACAC, located at the –356 to –364 region of the promoter could in fact be refined to a 7-bp CGCCACA motif that is also repeated at –333 to –340. The second copy of this motif was essential for activity, since mutations in the core region of the second copy completely abolished activity and regulation by sulphur sources. Activity, but not regulation, could be restored by reintroducing an additional copy upstream of the first copy. A third region, GCCGTCTGCAAGGCA, conserved in the HGT1 promoters of the different Saccharomyces spp, was observed at –300 to –285 but, while mutations in this region did not lead to any loss in repression, the basal and induced levels were significantly increased. In contrast to a previous report, no evidence was found for regulation by the VDE endonuclease. The strong repression at the transport level by glutathione seen in strains overexpressing HGT1 was due to a glutathione-dependent toxicity in these cells. 相似文献
28.
Daselaar SM Veltman DJ Rombouts SA Raaijmakers JG Jonker C 《Neurobiology of aging》2003,24(7):1005-1011
Age-related impairments in episodic memory have been related to a deficiency in semantic processing, based on the finding that elderly adults typically benefit less than young adults from deep, semantic as opposed to shallow, nonsemantic processing of study items. In the present study, we tested the hypothesis that elderly adults are not able to perform certain cognitive operations under deep processing conditions. We further hypothesised that this inability does not involve regions commonly associated with lexical/semantic retrieval processes, but rather involves a dysfunction of the medial temporal lobe (MTL) memory system. To this end, we used functional MRI on rather extensive groups of young and elderly adults to compare brain activity patterns obtained during a deep (living/nonliving) and a shallow (uppercase/lowercase) classification task. Common activity in relation to semantic classification was observed in regions that have been previously related to semantic retrieval, including mainly left-lateralised activity in the inferior prefrontal, middle temporal, and middle frontal/anterior cingulate gyrus. Although the young adults showed more activity in some of these areas, the finding of mainly overlapping activation patterns during semantic classification supports the idea that lexical/semantic retrieval processes are still intact in elderly adults. This received further support by the finding that both groups showed similar behavioural performances as well on the deep and shallow classification tasks. Importantly, though, the young revealed significantly more activity than the elderly adults in the left anterior hippocampus during deep relative to shallow classification. This finding is in line with the idea that age-related impairments in episodic encoding are, at least partly, due to an under-recruitment of the medial temporal lobe memory system. 相似文献
29.
Modulation of Whole-Cell Currents in Plasmodium Falciparum-Infected Human Red Blood Cells by Holding Potential and Serum 总被引:3,自引:0,他引:3
Henry M. Staines Trevor Powell J. Clive Ellory Stéphane Egée Franck Lapaix Gaëtan Decherf Serge L. Y. Thomas Christophe Duranton† Florian Lang† Stephan M. Huber† 《The Journal of physiology》2003,552(1):177-183
Recent electrophysiological studies have identified novel ion channel activity in the host plasma membrane of Plasmodium falciparum -infected human red blood cells (RBCs). However, conflicting data have been published with regard to the characteristics of induced channel activity measured in the whole-cell configuration of the patch-clamp technique. In an effort to establish the reasons for these discrepancies, we demonstrate here two factors that have been found to modulate whole-cell recordings in malaria-infected RBCs. Firstly, negative holding potentials reduced inward currents (i.e. at negative potentials), although this result was highly complex. Secondly, the addition of human serum increased outward currents (i.e. at positive potentials) by approximately 4-fold and inward currents by approximately 2-fold. These two effects may help to resolve the conflicting data in the literature, although further investigation is required to understand the underlying mechanisms and their physiological relevance in detail. 相似文献
30.
Nguyen Khac F Waill MC Romana SP Radford-Weiss I Busson M Collonge-Rame MA Ribadeau-Dumas A Piffaut MC Daniel MT Davi F Merle-Béral H Berger R Arock M 《Cancer Genetics and Cytogenetics》2002,138(1):22-26
Two patients with Ph-positive chronic myelocytic leukemia in erythroblastic transformation and rearrangement of the short arm of chromosome 18 are reported. Fluorescence in situ hybridization studies showed that the 18p rearrangement resulted from translocation of the main part of chromosome 22 long arm to 18p, including BCR-ABL1 fusion. The 18p abnormality resulted, thus, in loss of 18p and duplication of BCR-ABL1 in both patients. The possible relation to the erythroblastic type of blastic phase is briefly discussed. In addition an apparently intact germline ABL1 gene was duplicated and inserted into chromosome 6 at band p21 in one of these patients. 相似文献