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McConnell NJ Ma CP Gebhardt K Wright SA Murphy JD Lauer TR Graham JR Richstone DO 《Nature》2011,480(7376):215-218
Observational work conducted over the past few decades indicates that all massive galaxies have supermassive black holes at their centres. Although the luminosities and brightness fluctuations of quasars in the early Universe suggest that some were powered by black holes with masses greater than 10 billion solar masses, the remnants of these objects have not been found in the nearby Universe. The giant elliptical galaxy Messier 87 hosts the hitherto most massive known black hole, which has a mass of 6.3 billion solar masses. Here we report that NGC 3842, the brightest galaxy in a cluster at a distance from Earth of 98 megaparsecs, has a central black hole with a mass of 9.7 billion solar masses, and that a black hole of comparable or greater mass is present in NGC 4889, the brightest galaxy in the Coma cluster (at a distance of 103 megaparsecs). These two black holes are significantly more massive than predicted by linearly extrapolating the widely used correlations between black-hole mass and the stellar velocity dispersion or bulge luminosity of the host galaxy. Although these correlations remain useful for predicting black-hole masses in less massive elliptical galaxies, our measurements suggest that different evolutionary processes influence the growth of the largest galaxies and their black holes. 相似文献
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The neurons of layer 4 in the adult cerebral cortex receive their major ascending inputs from the thalamus. In development, however, thalamic axons arrive at the appropriate cortical area long before their target layer 4 neurons have migrated into the cortical plate. The axons accumulate and wait in the zone below the cortical plate, the subplate, for several weeks before invading the cortical plate. The subplate is a transient zone that contains the first postmitotic neurons of the telencephalon. These neurons mature well before other cortical neurons, and disappear by cell death after the thalamic axons have grown into the overlying cortical plate. The close proximity of growing thalamocortical axons and subplate neurons suggests that they might be involved in interactions important for normal thalamocortical development. Here we show that early in development the deletion of subplate neurons located beneath visual cortex prevents axons from the lateral geniculate nucleus of the thalamus from recognizing and innervating visual cortex, their normal target. In the absence of subplate neurons, lateral geniculate nucleus axons continue to grow in the white matter past visual cortex despite the presence of their target layer 4 neurons. Thus the transient subplate neurons are necessary for appropriate cortical target selection by thalamocortical axons. 相似文献
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Rajalakshmi Nambiar Russell E. McConnell Matthew J. Tyska 《Cellular and molecular life sciences : CMLS》2010,67(8):1239-1254
Cells build plasma membrane protrusions supported by parallel bundles of F-actin to enable a wide variety of biological functions,
ranging from motility to host defense. Filopodia, microvilli and stereocilia are three such protrusions that have been the
focus of intense biological and biophysical investigation in recent years. While it is evident that actin dynamics play a
significant role in the formation of these organelles, members of the myosin superfamily have also been implicated as key
players in the maintenance of protrusion architecture and function. Based on a simple analysis of the physical forces that
control protrusion formation and morphology, as well as our review of available data, we propose that myosins play two general
roles within these structures: (1) as cargo transporters to move critical regulatory components toward distal tips and (2)
as mediators of membrane-cytoskeleton adhesion. 相似文献
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O. J. McConnell R. Longley M. Gunasekera 《Cellular and molecular life sciences : CMLS》1992,48(9):891-892
Isometachromin (1), a new sesquiterpene-quinone that is related structurally to metachromin C (2), and the known compounds ilimaquinone (3) and and 5-epi-ilimaquinone (4), were isolated from a deep water sponge in the family Spongiidae; the structure of isometachromin was elucidated by spectral methods. Isometachromin exhibits in vitro cytotoxicity against the human lung cancer cell line A 549 (IC50=2.6 g/ml), but not against P 388 murine leukemia (IC5010 g/ml) and also exhibits antimicrobial activity.This research is Harbor Branch Oceanographic Institution (HBOI) contribution number 911. We thank Drs S. A. Pomponi and M. Kelly-Borges (HBOI) for sponge taxonomy, and Dr P. McCarthy and T. Peterson (HBOI) for antimicrobial data. 相似文献
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C. J. McConnell G. M. Wright M. E. DeMont 《Cellular and molecular life sciences : CMLS》1996,52(9):918-921
The presence of elastic fibres in the extracellular matrix (ECM) provides physiologically important elastic properties for many tissues. Until recently, microfibrils, one component of the ECM, were thought primarily to serve as a scaffolding on which elastin is deposited during development to form elaunin fibres [1]. The most prominent protein that forms mammalian microfibrils is fibrillin. It is known that mutations in the fibrillin gene cause a heterogenous connective tissue disease called marfan syndrome [2], so information on mechanical properties of microfibrils or their role in tissue function would be useful. Microfibrils are also found in the ECM of some invertebrate tissues, and there is growing evidence that the protein forming the structure is homologous to mammalian fibrillin [3, 4]. It has been shown that the microfibril-based arterial wall of the lobster has viscoelastic properties [5], and we have now utilized this primitive artery to measure the modulus of elasticity of microfibrils. It is similar to that of the rubber-like protein elastin. 相似文献
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Guo DC Pannu H Tran-Fadulu V Papke CL Yu RK Avidan N Bourgeois S Estrera AL Safi HJ Sparks E Amor D Ades L McConnell V Willoughby CE Abuelo D Willing M Lewis RA Kim DH Scherer S Tung PP Ahn C Buja LM Raman CS Shete SS Milewicz DM 《Nature genetics》2007,39(12):1488-1493
The major function of vascular smooth muscle cells (SMCs) is contraction to regulate blood pressure and flow. SMC contractile force requires cyclic interactions between SMC alpha-actin (encoded by ACTA2) and the beta-myosin heavy chain (encoded by MYH11). Here we show that missense mutations in ACTA2 are responsible for 14% of inherited ascending thoracic aortic aneurysms and dissections (TAAD). Structural analyses and immunofluorescence of actin filaments in SMCs derived from individuals heterozygous for ACTA2 mutations illustrate that these mutations interfere with actin filament assembly and are predicted to decrease SMC contraction. Aortic tissues from affected individuals showed aortic medial degeneration, focal areas of medial SMC hyperplasia and disarray, and stenotic arteries in the vasa vasorum due to medial SMC proliferation. These data, along with the previously reported MYH11 mutations causing familial TAAD, indicate the importance of SMC contraction in maintaining the structural integrity of the ascending aorta. 相似文献
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