The Galaxy Structure-Redshift Relationship

There exists a gradual, but persistent, evolutionary effect in the galaxy population such that galaxy structure and morphology change with redshift. This galaxy structure-redshift relationship is such that an increasingly large fraction of all bright and massive galaxies at redshifts 2 < z < 3 are morphologically peculiar at wavelengths from rest-frame ultraviolet to rest-frame optical. There are however examples of morphologically selected spirals and ellipticals at all redshifts up to z ~ 3. At lower redshift, the bright galaxy population smoothly transforms into normal ellipticals and spirals. The rate of this transformation strongly depends on redshift, with the swiftest evolution occurring between 1 < z < 2. This review characterizes the galaxy structure-redshift relationship, discusses its various physical causes, and how these are revealing the mechanisms responsible for galaxy formation.Comment: 20 pages, 8 figures. Invited Review to appear in "Penetrating Bars Through Masks of Cosmic Dust: The Hubble Tuning Fork Strikes A New Note", ed. D. Block et a

A Novel Universal Primer-Multiplex-PCR Method with Sequencing Gel Electrophoresis Analysis

In this study, a novel universal primer-multiplex-PCR (UP-M-PCR) method adding a universal primer (UP) in the multiplex PCR reaction system was described. A universal adapter was designed in the 5′-end of each specific primer pairs which matched with the specific DNA sequences for each template and also used as the universal primer (UP). PCR products were analyzed on sequencing gel electrophoresis (SGE) which had the advantage of exhibiting extraordinary resolution. This method overcame the disadvantages rooted deeply in conventional multiplex PCR such as complex manipulation, lower sensitivity, self-inhibition and amplification disparity resulting from different primers, and it got a high specificity and had a low detection limit of 0.1 ng for single kind of crops when screening the presence of genetically modified (GM) crops in mixture samples. The novel developed multiplex PCR assay with sequencing gel electrophoresis analysis will be useful in many fields, such as verifying the GM status of a sample irrespective of the crop and GM trait and so on

High Antipredatory Efficiency of Insular Lizards: A Warning Signal of Excessive Specimen Collection?

We live-captured lizards on islands in the Gulf of California and the Baja California peninsula mainland, and compared their ability to escape predation. Contrary to expectations, endemic lizard species from uninhabited islands fled from humans earlier and more efficiently than those from peninsular mainland areas. In fact, 58.2% (n = 146) of the lizards we tried to capture on the various islands escaped successfully, while this percentage was only 14.4% (n = 160) on the peninsular mainland. Separate evidence (e.g., proportion of regenerated tails, low human population at the collection areas, etc.) challenges several potential explanations for the higher antipredatory efficiency of insular lizards (e.g., more predation pressure on islands, habituation to humans on the peninsula, etc.). Instead, we suggest that the ability of insular lizards to avoid predators may be related to harvesting by humans, perhaps due to the value of endemic species as rare taxonomic entities. If this hypothesis is correct, predation-related behavioral changes in rare species could provide early warning signals of their over-exploitation, thus encouraging the adoption of conservation measures

The Secreted Metalloprotease ADAMTS20 Is Required for Melanoblast Survival

ADAMTS20 (A disintegrin-like and metalloprotease domain with thrombospondin type-1 motifs) is a member of a family of secreted metalloproteases that can process a variety of extracellular matrix (ECM) components and secreted molecules. Adamts20 mutations in belted (bt) mice cause white spotting of the dorsal and ventral torso, indicative of defective neural crest (NC)-derived melanoblast development. The expression pattern of Adamts20 in dermal mesenchymal cells adjacent to migrating melanoblasts led us to initially propose that Adamts20 regulated melanoblast migration. However, using a Dct-LacZ transgene to track melanoblast development, we determined that melanoblasts were distributed normally in whole mount E12.5 bt/bt embryos, but were specifically reduced in the trunk of E13.5 bt/bt embryos due to a seven-fold higher rate of apoptosis. The melanoblast defect was exacerbated in newborn skin and embryos from bt/bt animals that were also haploinsufficient for Adamts9, a close homolog of Adamts20, indicating that these metalloproteases functionally overlap in melanoblast development. We identified two potential mechanisms by which Adamts20 may regulate melanoblast survival. First, skin explant cultures demonstrated that Adamts20 was required for melanoblasts to respond to soluble Kit ligand (sKitl). In support of this requirement, bt/bt;Kittm1Alf/+ and bt/bt;KitlSl/+ mice exhibited synergistically increased spotting. Second, ADAMTS20 cleaved the aggregating proteoglycan versican in vitro and was necessary for versican processing in vivo, raising the possibility that versican can participate in melanoblast development. These findings reveal previously unrecognized roles for Adamts proteases in cell survival and in mediating Kit signaling during melanoblast colonization of the skin. Our results have implications not only for understanding mechanisms of NC-derived melanoblast development but also provide insights on novel biological functions of secreted metalloproteases

Programmable Ligand Detection System in Plants through a Synthetic Signal Transduction Pathway

There is an unmet need to monitor human and natural environments for substances that are intentionally or unintentionally introduced. A long-sought goal is to adapt plants to sense and respond to specific substances for use as environmental monitors. Computationally re-designed periplasmic binding proteins (PBPs) provide a means to design highly sensitive and specific ligand sensing capabilities in receptors. Input from these proteins can be linked to gene expression through histidine kinase (HK) mediated signaling. Components of HK signaling systems are evolutionarily conserved between bacteria and plants. We previously reported that in response to cytokinin-mediated HK activation in plants, the bacterial response regulator PhoB translocates to the nucleus and activates transcription. Also, we previously described a plant visual response system, the de-greening circuit, a threshold sensitive reporter system that produces a visual response which is remotely detectable and quantifiable.We describe assembly and function of a complete synthetic signal transduction pathway in plants that links input from computationally re-designed PBPs to a visual response. To sense extracellular ligands, we targeted the computational re-designed PBPs to the apoplast. PBPs bind the ligand and develop affinity for the extracellular domain of a chemotactic protein, Trg. We experimentally developed Trg fusions proteins, which bind the ligand-PBP complex, and activate intracellular PhoR, the HK cognate of PhoB. We then adapted Trg-PhoR fusions for function in plants showing that in the presence of an external ligand PhoB translocates to the nucleus and activates transcription. We linked this input to the de-greening circuit creating a detector plant.Our system is modular and PBPs can theoretically be designed to bind most small molecules. Hence our system, with improvements, may allow plants to serve as a simple and inexpensive means to monitor human surroundings for substances such as pollutants, explosives, or chemical agents

The endogenous proteoglycan-degrading enzyme ADAMTS-4 promotes functional recovery after spinal cord injury

<p>Abstract</p> <p>Background</p> <p>Chondroitin sulfate proteoglycans are major inhibitory molecules for neural plasticity under both physiological and pathological conditions. The chondroitin sulfate degrading enzyme chondroitinase ABC promotes functional recovery after spinal cord injury, and restores experience-dependent plasticity, such as ocular dominance plasticity and fear erasure plasticity, in adult rodents. These data suggest that the sugar chain in a proteoglycan moiety is essential for the inhibitory activity of proteoglycans. However, the significance of the core protein has not been studied extensively. Furthermore, considering that chondroitinase ABC is derived from bacteria, a mammalian endogenous enzyme which can inactivate the proteoglycans' activity is desirable for clinical use.</p> <p>Methods</p> <p>The degradation activity of ADAMTS-4 was estimated for the core proteins of chondroitin sulfate proteoglycans, that is, brevican, neurocan and phosphacan. To evaluate the biological significance of ADMATS-4 activity, an <it>in vitro </it>neurite growth assay and an <it>in vivo </it>neuronal injury model, spinal cord contusion injury, were employed.</p> <p>Results</p> <p>ADAMTS-4 digested proteoglycans, and reversed their inhibition of neurite outgrowth. Local administration of ADAMTS-4 significantly promoted motor function recovery after spinal cord injury. Supporting these findings, the ADAMTS-4-treated spinal cord exhibited enhanced axonal regeneration/sprouting after spinal cord injury.</p> <p>Conclusions</p> <p>Our data suggest that the core protein in a proteoglycan moiety is also important for the inhibition of neural plasticity, and provides a potentially safer tool for the treatment of neuronal injuries.</p

Towards modeling the retailer as a brand: A social construction of the grocery store from the customer standpoint

As a highly customer-sensitive business, retailing is one of the most socially active industries. Nevertheless, when addressing retailers as brands, the retailing literature has failed to account for their unique social orientation, exposing a gap in the literature. This paper utilizes the sociological view of brands to socially construct a conceptual retail brand model from the customer standpoint. An ethnographic study of grocery retailing revealed that the store has, metaphorically, a tree-shaped culture, which can organically model the interplay between building the retailer brand as a culture and the phases constituting the social-self concept

Modeling the accretion history of supermassive black holes

There is overwhelming evidence for the presence of supermassive black holes (SMBHs) in the centers of most nearby galaxies. The mass estimates for these remnant black holes from the stellar kinematics of local galaxies and the quasar phenomenon at high redshifts point to the presence of assembled SMBHs. The accretion history of SMBHs can be reconstructed using observations at high and low redshifts as model constraints. Observations of galaxies and quasars in the submillimeter, infrared, optical, and X-ray wavebands are used as constraints, along with data from the demography of local black holes. Theoretical modeling of the growth of black hole mass with cosmic time has been pursued thus far in two distinct directions: a phenomenological approach that utilizes observations in various wavebands, and a semi-analytic approach that starts with a theoretical framework and a set of assumptions with a view to matching observations. Both techniques have been pursued in the context of the standard paradigm for structure formation in a Cold Dark Matter dominated universe. Here, we examine the key issues and uncertainties in the theoretical understanding of the growth of SMBHs.Comment: 19 pages, 4 figures, to appear as Chapter 4 in "Supermassive Black Holes in the Distant Universe" (2004), ed. A. J. Barger, Kluwer Academic Publishers, in pres