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Iodinated vinculin, metavinculin and α-actinin were used to probe the interaction of these proteins with electrophoretically separated cytoskeletal proteins. Using the gel overlay technique, we detected strong binding of 125I-vinculin and 125I-metavinculin to α-actinin, 175 kDa polypeptide, talin, vinculin and metavinculin themselves, and moderate binding to actin.125I-α-actinin was capable of interacting with vinculin and metavinculin. The specific binding of 125-I-α-actinin to vinculin and metavinculin immobilized on a polysterene surface was also demonstrated. We suggest that the ability of vinculin and α-actinin to form a complex may be realized in microfilament-membrane linkages. 相似文献
4.
Resistance of Spirulina platensis to Ammonia at High pH Values 总被引:2,自引:0,他引:2
Spirulina platensis is an alkalophilic cyanobacterium, exhibitingoptimal growth at pH 9.0 to 10.0. It grows well at pH 11.5 butnot at pH 7.0. Unlike many other photosynthetic microorganisms,it is capable of utilizing ammonia3 even at high pH values,and is resistant to the ammonia-mediated uncoupling of photosynthesis.The entry of ammonia into the cells is pH-dependent, and islimited by a relatively high average internal pH. This highpH value appears to be maintained predominantly by a high intrathylakoidpH. (Received November 20, 1990; Accepted July 3, 1991) 相似文献
5.
Localization of talin in skeletal and cardiac muscles 总被引:2,自引:0,他引:2
Antibodies to talin and vinculin were used for localization of these proteins in skeletal and cardiac muscles by the indirect immunofluorescence method. We have found that talin is localized in intercalated discs of cardiac muscle and in costameres of skeletal and cardiac muscles. It is suggested that in striated muscles talin and vinculin play an important role in interactions between actin filaments and membranes. 相似文献
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A Synechococcus PglnA::luxAB Fusion for Estimation of Nitrogen Bioavailability to Freshwater Cyanobacteria 下载免费PDF全文
Osnat Gillor Ayelet Harush Ora Hadas Anton F. Post Shimshon Belkin 《Applied microbiology》2003,69(3):1465-1474
In contrast to extensive studies of phosphorus, widely considered the main nutrient limiting phytoplankton biomass in freshwater ecosystems, there have been few studies on the role of nitrogen in controlling phytoplankton populations. This situation may be due partly to the complexity in estimating its utilization and bioavailability. In an attempt to provide a novel tool for this purpose, we fused the promoter of the glutamine synthetase-encoding gene, P glnA, from Synechococcus sp. strain PCC7942 to the luxAB luciferase-encoding genes of the bioluminescent bacterium Vibrio harveyi. The resulting construct was introduced into a neutral site on the Synechococcus chromosome to yield the reporter strain GSL. Light emission by this strain was dependent upon ambient nitrogen concentrations. The linear response range of the emitted luminescence was 1 mM to 1 μM for the inorganic nitrogen species tested (ammonium, nitrate, and nitrite) and 10- to 50-fold lower for glutamine and urea. When water samples collected from along a depth profile in Lake Kinneret (Israel) were exposed to the reporter strain, the bioluminescence of the reporter strain mirrored the total dissolved nitrogen concentrations determined for the same samples and was shown to be a sensitive indicator of the concentration of bioavailable nitrogen. 相似文献
7.
J L Duband A M Belkin J Syfrig J P Thiery V E Koteliansky 《Development (Cambridge, England)》1992,116(3):585-600
In this study, we have examined the spatiotemporal distribution of the alpha 1 integrin subunit, a putative laminin and collagen receptor, in avian embryos, using immunofluorescence microscopy and immunoblotting techniques. We used an antibody raised against a gizzard 175 x 10(3) M(r) membrane protein which was described previously and which we found to be immunologically identical to the chicken alpha 1 integrin subunit. In adult avian tissues, alpha 1 integrin exhibited a very restricted pattern of expression; it was detected only in smooth muscle and in capillary endothelial cells. In the developing embryo, alpha 1 integrin subunit expression was discovered in addition to smooth muscle and capillary endothelial cells, transiently, in both central and peripheral nervous systems and in striated muscles, in association with laminin and collagen IV. alpha 1 integrin was practically absent from most epithelial tissues, including the liver, pancreas and kidney tubules, and was weakly expressed by tissues that were not associated with laminin and collagen IV. In the nervous system, alpha 1 integrin subunit expression occurred predominantly at the time of early neuronal differentiation. During skeletal muscle development, alpha 1 integrin was expressed on myogenic precursors, during myoblast migration, and in differentiating myotubes. alpha 1 integrin disappeared from skeletal muscle cells as they became contractile. In visceral and vascular smooth muscles, alpha 1 integrin appeared specifically during early smooth muscle cell differentiation and, later, was permanently expressed after cell maturation. These results indicate that (i) the expression pattern of alpha 1 integrin is consistent with a function as a laminin/collagen IV receptor; (ii) during avian development, expression of the alpha 1 integrin subunit is spatially and temporally regulated; (iii) during myogenesis and neurogenesis, expression of alpha 1 integrin is transient and correlates with cell migration and differentiation. 相似文献
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Drop-size soda lakes: transient microbial habitats on a salt-secreting desert tree 总被引:1,自引:0,他引:1 下载免费PDF全文
We describe a hitherto unrecognized bacterial community, inhabiting the leaf surfaces of the salt-excreting desert tree Tamarix. High temperatures, strong radiation, and very low humidity dictate a daytime existence in complete desiccation, but damp nights allow the microbial population to proliferate in a sugar-rich, alkaline, and hypersaline solution, before drying up again after sunrise. The exclusively bacterial population contains many undescribed species and genera, but nevertheless appears to be characterized by relatively limited species diversity. Sequences of 16S rRNA genes from either isolates or total community DNA place the identified members of the community in five bacterial groups (Actinobacteria, Bacteroidetes, Firmicutes, alpha-, and gamma-Proteobacteria); in each of these, they concentrate in a very narrow branch that in most cases harbors organisms isolated from unrelated halophilic environments. 相似文献
9.
Rho-mediated Contractility Exposes a Cryptic Site in Fibronectin and Induces Fibronectin Matrix Assembly 总被引:17,自引:2,他引:17 下载免费PDF全文
Cuiling Zhong Magdalena Chrzanowska-Wodnicka James Brown Amy Shaub Alexey M. Belkin Keith Burridge 《The Journal of cell biology》1998,141(2):539-551
Many factors influence the assembly of fibronectin into an insoluble fibrillar extracellular matrix. Previous work demonstrated that one component in serum that promotes the assembly of fibronectin is lysophosphatidic acid (Zhang, Q., W.J. Checovich, D.M. Peters, R.M. Albrecht, and D.F. Mosher. 1994. J. Cell Biol. 127:1447–1459). Here we show that C3 transferase, an inhibitor of the low molecular weight GTP-binding protein Rho, blocks the binding of fibronectin and the 70-kD NH2-terminal fibronectin fragment to cells and blocks the assembly of fibronectin into matrix induced by serum or lysophosphatidic acid. Microinjection of recombinant, constitutively active Rho into quiescent Swiss 3T3 cells promotes fibronectin matrix assembly by the injected cells. Investigating the mechanism by which Rho promotes fibronectin polymerization, we have used C3 to determine whether integrin activation is involved. Under conditions where C3 decreases fibronectin assembly we have only detected small changes in the state of integrin activation. However, several inhibitors of cellular contractility, that differ in their mode of action, inhibit cell binding of fibronectin and the 70-kD NH2-terminal fibronectin fragment, decrease fibronectin incorporation into the deoxycholate insoluble matrix, and prevent fibronectin's assembly into fibrils on the cell surface. Because Rho stimulates contractility, these results suggest that Rho-mediated contractility promotes assembly of fibronectin into a fibrillar matrix. One mechanism by which contractility could enhance fibronectin assembly is by tension exposing cryptic self-assembly sites within fibronectin that is being stretched. Exploring this possibility, we have found a monoclonal antibody, L8, that stains fibronectin matrices differentially depending on the state of cell contractility. L8 was previously shown to inhibit fibronectin matrix assembly (Chernousov, M.A., A.I. Faerman, M.G. Frid, O.Y. Printseva, and V.E. Koteliansky. 1987. FEBS (Fed. Eur. Biochem. Soc.) Lett. 217:124–128). When it is used to stain normal cultures that are developing tension, it reveals a matrix indistinguishable from that revealed by polyclonal anti-fibronectin antibodies. However, the staining of fibronectin matrices by L8 is reduced relative to the polyclonal antibody when the contractility of cells is inhibited by C3. We have investigated the consequences of mechanically stretching fibronectin in the absence of cells. Applying a 30–35% stretch to immobilized fibronectin induced binding of soluble fibronectin, 70-kD fibronectin fragment, and L8 monoclonal antibody. Together, these results provide evidence that self-assembly sites within fibronectin are exposed by tension. 相似文献
10.
Belkin GS 《Perspectives in biology and medicine》2004,47(3):372-385
From both within and without bioethics, growing criticism of the predominant methods and practices of the field can be heard. These critiques tend to lament an emphasis on logically derived rules and philosophical theories that inadequately capture how and why people have the moral attitudes they do, and they urge the use of more empirically grounded social sciences--history, sociology, and anthropology--to draw attention to the complex factors behind such attitudes. However, these critiques do not go far enough, as they do not question why debate over ethical categories should have such a central role in voicing concerns about medicine. The importance of using other forms of inquiry, especially that of history, to examine aspects of medical practice and the emergence of bioethics itself is not simply to refine bioethical moral analysis. Instead, history can be employed to counter the preoccupation with translating concerns about medicine into moral terms and to move towards what is more sorely needed: a true medical humanism. 相似文献