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81.
The irregular xylem 2 mutant is an allele of korrigan that affects the secondary cell wall of Arabidopsis thaliana 总被引:6,自引:0,他引:6
Szyjanowicz PM McKinnon I Taylor NG Gardiner J Jarvis MC Turner SR 《The Plant journal : for cell and molecular biology》2004,37(5):730-740
The irregular xylem 2 (irx2) mutant of Arabidopsis thaliana exhibits a cellulose deficiency in the secondary cell wall, which is brought about by a point mutation in the KORRIGAN (KOR) beta,1-4 endoglucanase (beta,1-4 EGase) gene. Measurement of the total crystalline cellulose in the inflorescence stem indicates that the irx2 mutant contains approximately 30% of the level present in the wild type (WT). Fourier-Transform Infra Red (FTIR) analysis, however, indicates that there is no decrease in cellulose in primary cell walls of the cortical and epidermal cells of the stem. KOR expression is correlated with cellulose synthesis and is highly expressed in cells synthesising a secondary cell wall. Co-precipitation experiments, using either an epitope-tagged form of KOR or IRX3 (AtCesA7), suggest that KOR is not an integral part of the cellulose synthase complex. These data are supported by immunolocalisation of KOR that suggests that KOR does not localise to sites of secondary cell wall deposition in the developing xylem. The defect in irx2 plant is consistent with a role for KOR in the later stages of secondary cell wall formation, suggesting a role in processing of the growing microfibrils or release of the cellulose synthase complex. 相似文献
82.
Cell-specific expression of SERCA, the exogenous Ca2+ transport ATPase, in cardiac myocytes 总被引:1,自引:0,他引:1
Ma H Sumbilla CM Farrance IK Klein MG Inesi G 《American journal of physiology. Cell physiology》2004,286(3):C556-C564
We evaluated various constructs to obtain cell-specific expression of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) gene in cardiac myocytes after cDNA transfer by means of transfections or infections with adenovirus vectors. Expression of exogenous enhanced green fluorescent protein (EGFP) and SERCA genes was studied in cultured chicken embryo and neonatal rat cardiac myocytes, skeletal and smooth muscle cells, fibroblasts, and hepatocytes. Whereas the cytomegalovirus (CMV) promoter yielded high levels of protein expression in all cells studied, cardiac troponin T (cTnT) promoter segments demonstrated high specificity for cardiac myocytes. Their efficiency for protein expression was lower than that of the CMV promoter, but higher than that of cardiac myosin light chain or -myosin heavy chain promoter segments. A double virus system for Cre-dependent expression under control of the CMV promoter and Cre expression under control of a cardiac-specific promoter yielded high protein levels in cardiac myocytes, but only partial cell specificity due to significant Cre expression in hepatocytes. Specific intracellular targeting of gene products was demonstrated in situ by specific immunostaining of exogenous SERCA1 and endogenous SERCA2 and comparative fluorescence microscopy. The -374 cTnT promoter segment was the most advantageous of the promoters studied, producing cell-specific SERCA expression and a definite increase over endogenous Ca2+-ATPase activity as well as faster removal of cytosolic calcium after membrane excitation. We conclude that analysis of promoter efficiency and cell specificity is of definite advantage when cell-specific expression of exogenous SERCA is wanted in cardiac myocytes after cDNA delivery to mixed cell populations. cardiac myocytes; cell-specific expression; adenovirus vectors; calcium transport 相似文献
83.
84.
Independent regulation of synaptic size and activity by the anaphase-promoting complex 总被引:8,自引:0,他引:8
Neuronal plasticity relies on tightly regulated control of protein levels at synapses. One mechanism to control protein abundance is the ubiquitin-proteasome degradation system. Recent studies have implicated ubiquitin-mediated protein degradation in synaptic development, function, and plasticity, but little is known about the regulatory mechanisms controlling ubiquitylation in neurons. In contrast, ubiquitylation has long been studied as a central regulator of the eukaryotic cell cycle. A critical mediator of cell-cycle transitions, the anaphase-promoting complex/cyclosome (APC/C), is an E3 ubiquitin ligase. Although the APC/C has been detected in several differentiated cell types, a functional role for the complex in postmitotic cells has been elusive. We describe a novel postmitotic role for the APC/C at Drosophila neuromuscular synapses: independent regulation of synaptic growth and synaptic transmission. In neurons, the APC/C controls synaptic size via a downstream effector Liprin-alpha; in muscles, the APC/C regulates synaptic transmission, controlling the concentration of a postsynaptic glutamate receptor. 相似文献
85.
McKendrick IJ 《Alternatives to laboratory animals : ATLA》2004,32(Z2):23-27
Several of the Scottish Agricultural and Biological Research Institutes carry out research on domestic animal health and welfare. Statistical services are provided by Biomathematics & Statistics Scotland, a sister research organisation. At one of these institutes, a statistician has been an integral member of the animal experiments and ethics committee for over 10 years, and each animal experiment is examined by the committee statistician as part of the review process. This paper will describe this review process, and then discuss those areas in which statistical advice has had most impact in the reduction of animal numbers. It is suggested that most benefit does not come from simple sample-size calculations, but rather from the application of the principles of good experimental design and close collaboration between the scientist and the statistician in the design and analysis of experiments. The final conclusion is that scientists welcome constructive, long-term statistical input, although budgetary issues can prove to be a barrier. 相似文献
86.
Importin alpha associates with membranes and participates in nuclear envelope assembly in vitro
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Importin alpha is well known as an adaptor that functions with Importin beta in the nuclear import of proteins containing specific nuclear localization signals (NLSs). We show here that either an excess or a lack of Importin alpha blocks nuclear envelope (NE) assembly in vitro, and our data suggest that soluble Importin alpha functions in NE assembly in conjunction with NLS-containing partner proteins. Surprisingly, a significant proportion of Importin alpha is found to fractionate with Xenopus egg membranes. We demonstrate that membrane association of Importin alpha is regulated by phosphorylation. Using mutant forms of Importin alpha that either do not bind membranes or are not released from them by phosphorylation, we provide evidence that membrane-associated Importin alpha is required for NE formation. Unlike other functions of Importin alpha, this membrane-associated activity does not require interaction with NLS proteins. 相似文献
87.
A selection of 1-amino-substituted beta-carbolines have been prepared by amination of 1-chloro-beta-carboline as simple mimics of manzamine A and chloroquine and their intercalating ability, anticancer and antimalarial activity were studied. 相似文献
88.
Walters I Bennion C Connolly S Croshaw PJ Hardy K Hartopp P Jackson CG King SJ Lawrence L Mete A Murray D Robinson DH Stein L Wells E John Withnall W 《Bioorganic & medicinal chemistry letters》2004,14(14):3645-3649
The high lipophilicity of a series of cytosolic phospholipase A(2) inhibitors has been reduced by the modification of a decyloxyphenyl chain designed to mimic the arachidonyl group of the natural substrate. These changes have resulted in an improvement in the whole cell potency of the inhibitors. 相似文献
89.
Petosa C Schoehn G Askjaer P Bauer U Moulin M Steuerwald U Soler-López M Baudin F Mattaj IW Müller CW 《Molecular cell》2004,16(5):761-775
CRM1/Exportin1 mediates the nuclear export of proteins bearing a leucine-rich nuclear export signal (NES) by forming a cooperative ternary complex with the NES-bearing substrate and the small GTPase Ran. We present a structural model of human CRM1 based on a combination of X-ray crystallography, homology modeling, and electron microscopy. The architecture of CRM1 resembles that of the import receptor transportin1, with 19 HEAT repeats and a large loop implicated in Ran binding. Residues critical for NES recognition are identified adjacent to the cysteine residue targeted by leptomycin B (LMB), a specific CRM1 inhibitor. We present evidence that a conformational change of the Ran binding loop accounts for the cooperativity of Ran- and substrate binding and for the selective enhancement of CRM1-mediated export by the cofactor RanBP3. Our findings indicate that a single architectural and mechanistic framework can explain the divergent effects of RanGTP on substrate binding by many import and export receptors. 相似文献
90.
Mitotic chromosomes must be organised into a highly ordered and compacted form to allow proper segregation of DNA during each round of cell division. Two new studies report observations of DNA compaction by eukaryotic and bacterial condensin molecules in real time using magnetic and optical trapping micromanipulation techniques. 相似文献