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排序方式: 共有952条查询结果,搜索用时 187 毫秒
71.
72.
Schwander M Leu M Stumm M Dorchies OM Ruegg UT Schittny J Müller U 《Developmental cell》2003,4(5):673-685
The mechanisms that regulate the formation of multinucleated muscle fibers from mononucleated myoblasts are not well understood. We show here that extracellular matrix (ECM) receptors of the beta1 integrin family regulate myoblast fusion. beta1-deficient myoblasts adhere to each other, but plasma membrane breakdown is defective. The integrin-associated tetraspanin CD9 that regulates cell fusion is no longer expressed at the cell surface of beta1-deficient myoblasts, suggesting that beta1 integrins regulate the formation of a protein complex important for fusion. Subsequent to fusion, beta1 integrins are required for the assembly of sarcomeres. Other ECM receptors such as the dystrophin glycoprotein complex are still expressed but cannot compensate for the loss of beta1 integrins, providing evidence that different ECM receptors have nonredundant functions in skeletal muscle fibers. 相似文献
73.
The western woolly lemur is distributed through central western, northwestern and possibly northern Madagascar and is traditionally viewed as a monotypic species (Avahi occidentalis) or as a subspecies of A. laniger. We present new data on body weights of Avahi which, together with previously available body weights, provide additional evidence for recognizing eastern and western woolly lemurs as two distinct species. We then reexamine the distributions of, and chromatic variation within and between, populations of western woolly lemurs. A comparative study of wild subjects and museum skins reveals that several geographically discrete morphs exist in western Avahi, which is clearly polytypic. Marked differences between populations in fur coloration suggest that 3 distinct taxa should be recognized. The populations differ considerably in their habitat structure. In addition, field observations suggest clear differences in population density between 2 of the populations. We describe and name one new species. 相似文献
74.
The Fur-Regulated Gene Encoding the Alternative Sigma Factor PvdS Is Required for Iron-Dependent Expression of the LysR-Type Regulator PtxR in Pseudomonas aeruginosa 总被引:3,自引:0,他引:3
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Michael L. Vasil Urs A. Ochsner Zaiga Johnson Jane A. Colmer Abdul N. Hamood 《Journal of bacteriology》1998,180(24):6784-6788
75.
76.
Agrin Can Mediate Acetylcholine Receptor Gene Expression in Muscle by Aggregation of Muscle-derived Neuregulins 总被引:7,自引:1,他引:6
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![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
77.
78.
Vincent Mutel Gerhard Trube Agnès Klingelschmidt Jürg Messer Zaiga Bleuel Urs Humbel Merwyn M. Clifford Gareth J. Ellis J. Grayson Richards 《Journal of neurochemistry》1998,71(1):418-426
Abstract: A new AMPA receptor antagonist, Ro 48-8587, was characterized pharmacologically in vitro. It is highly potent and selective for AMPA receptors as shown by its effects on [3 H]AMPA, [3 H]kainate, and [3 H]MK-801 binding to rat brain membranes and on AMPA- or NMDA-induced depolarization in rat cortical wedges. [3 H]Ro 48-8587 bound with a high affinity ( K D = 3 n M ) to a single population of binding sites with a B max of 1 pmol/mg of protein in rat whole brain membranes. [3 H]Ro 48-8587 binding to rat whole brain membranes was inhibited by several compounds with the following rank order of potency: Ro 48-8587 > 6-nitro-7-sulphamoylbenzo[ f ]quinoxaline-2,3-dione (NBQX) > YM 90K > 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) > quisqualate > AMPA > glutamate > kainate > NMDA. The distribution and abundance of specific binding sites (∼95% of total) in sections of rat CNS, revealed by quantitative receptor radioautography and image analysis, indicated a very discrete localization. Highest binding values were observed in cortical layers (binding in layers 1 and 2 > binding in layers 3–6), hippocampal formation, striatum, dorsal septum, reticular thalamic nucleus, cerebellar molecular layer, and spinal cord dorsal horn. At 1 n M , the values for specific binding were highest in the cortical layers 1 and 2 and lowest in the brainstem (∼2.6 and 0.4 pmol/mg of protein, respectively). Ro 48-8587 is a potent and selective AMPA receptor antagonist with improved binding characteristics (higher affinity, selectivity, and specific binding) compared with those previously reported. 相似文献
79.
Altered mechanisms of sympathetic activation during rhythmic forearm exercise in heart failure 总被引:4,自引:0,他引:4
Silber David H.; Sutliff Greg; Yang Qing X.; Smith Michael B.; Sinoway Lawrence I.; Leuenberger Urs A. 《Journal of applied physiology》1998,84(5):1551-1559
In congestive heart failure (CHF), themechanisms of exercise-induced sympathoexcitation are poorly defined.We compared the responses of sympathetic nerve activity directed tomuscle (MSNA) and to skin (SSNA, peroneal microneurography) duringrhythmic handgrip (RHG) at 25% of maximal voluntary contraction andduring posthandgrip circulatory arrest (PHG-CA) in CHF patients with those of an age-matched control group. During RHG, the CHF patients fatigued prematurely. At end exercise, the increase in MSNA was similarin both groups (CHF patients, n = 12;controls, n = 10). However, duringPHG-CA, in the controls MSNA returned to baseline, whereas it remainedelevated in CHF patients (P < 0.05).Similarly, at end exercise, the increase in SSNA was comparable in bothgroups (CHF patients, n = 11;controls, n = 12), whereas SSNAremained elevated during PHG-CA in CHF patients but not in the controls (P < 0.05). In a separate controlgroup (n = 6), even high-intensity static handgrip was not accompanied by sustained elevation of SSNAduring PHG-CA. 31P-nuclear magneticresonance spectroscopy during RHG demonstrated significant muscleacidosis and accumulation of inorganic phosphate in CHF patients(n = 7) but not in controls(n = 9). We conclude that in CHFpatients rhythmic forearm exercise leads to premature fatigue andaccumulation of muscle metabolites. The prominent PHG-CA response ofMSNA and SSNA in CHF patients suggests activation of the musclemetaboreflex. Because, in contrast to controls, in CHF patients bothMSNA and SSNA appear to be under muscle metaboreflex control, themechanisms and distribution of sympathetic outflow during exerciseappear to be different from normal. 相似文献
80.
DNA-tumor viruses comprise enveloped and non-enveloped agents that cause malignancies in a large variety of cell types and tissues by interfering with cell cycle control and immortalization. Those DNA-tumor viruses that replicate in the nucleus use cellular mechanisms to transport their genome and newly synthesized viral proteins into the nucleus. This requires cytoplasmic transport and nuclear import of their genome. Agents that employ this strategy include adenoviruses, hepadnaviruses, herpesviruses, and likely also papillomaviruses, and polyomaviruses, but not poxviruses which replicate in the cytoplasm. Here, we discuss how DNA-tumor viruses enter cells, take advantage of cytoplasmic transport, and import their DNA genome through the nuclear pore complex into the nucleus. Remarkably, nuclear import of incoming genomes does not necessarily follow the same pathways used by the structural proteins of the viruses during the replication and assembly phases of the viral life cycle. Understanding the mechanisms of DNA nuclear import can identify new pathways of cell regulation and anti-viral therapies. 相似文献