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1

Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic  

PubMed Central

The ascent of dinosaurs in the Triassic is an exemplary evolutionary radiation, but the earliest phase of dinosaur history remains poorly understood. Body fossils of close dinosaur relatives are rare, but indicate that the dinosaur stem lineage (Dinosauromorpha) originated by the latest Anisian (ca 242–244 Ma). Here, we report footprints from the Early–Middle Triassic of Poland, stratigraphically well constrained and identified using a conservative synapomorphy-based approach, which shifts the origin of the dinosaur stem lineage back to the Early Olenekian (ca 249–251 Ma), approximately 5–9 Myr earlier than indicated by body fossils, earlier than demonstrated by previous footprint records, and just a few million years after the Permian/Triassic mass extinction (252.3 Ma). Dinosauromorph tracks are rare in all Polish assemblages, suggesting that these animals were minor faunal components. The oldest tracks are quadrupedal, a morphology uncommon among the earliest dinosauromorph body fossils, but bipedality and moderately large body size had arisen by the Early Anisian (ca 246 Ma). Integrating trace fossils and body fossils demonstrates that the rise of dinosaurs was a drawn-out affair, perhaps initiated during recovery from the Permo-Triassic extinction. PMID:20926435

Brusatte, Stephen L.; Niedzwiedzki, Grzegorz; Butler, Richard J.

2011-01-01

2

Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage  

PubMed Central

Large-scale adaptive radiations might explain the runaway success of a minority of extant vertebrate clades. This hypothesis predicts, among other things, rapid rates of morphological evolution during the early history of major groups, as lineages invade disparate ecological niches. However, few studies of adaptive radiation have included deep time data, so the links between extant diversity and major extinct radiations are unclear. The intensively studied Mesozoic dinosaur record provides a model system for such investigation, representing an ecologically diverse group that dominated terrestrial ecosystems for 170 million years. Furthermore, with 10,000 species, extant dinosaurs (birds) are the most speciose living tetrapod clade. We assembled composite trees of 614–622 Mesozoic dinosaurs/birds, and a comprehensive body mass dataset using the scaling relationship of limb bone robustness. Maximum-likelihood modelling and the node height test reveal rapid evolutionary rates and a predominance of rapid shifts among size classes in early (Triassic) dinosaurs. This indicates an early burst niche-filling pattern and contrasts with previous studies that favoured gradualistic rates. Subsequently, rates declined in most lineages, which rarely exploited new ecological niches. However, feathered maniraptoran dinosaurs (including Mesozoic birds) sustained rapid evolution from at least the Middle Jurassic, suggesting that these taxa evaded the effects of niche saturation. This indicates that a long evolutionary history of continuing ecological innovation paved the way for a second great radiation of dinosaurs, in birds. We therefore demonstrate links between the predominantly extinct deep time adaptive radiation of non-avian dinosaurs and the phenomenal diversification of birds, via continuing rapid rates of evolution along the phylogenetic stem lineage. This raises the possibility that the uneven distribution of biodiversity results not just from large-scale extrapolation of the process of adaptive radiation in a few extant clades, but also from the maintenance of evolvability on vast time scales across the history of life, in key lineages. PMID:24802911

Benson, Roger B. J.; Campione, Nicolas E.; Carrano, Matthew T.; Mannion, Philip D.; Sullivan, Corwin; Upchurch, Paul; Evans, David C.

2014-01-01

3

Rates of dinosaur body mass evolution indicate 170 million years of sustained ecological innovation on the avian stem lineage.  

PubMed

Large-scale adaptive radiations might explain the runaway success of a minority of extant vertebrate clades. This hypothesis predicts, among other things, rapid rates of morphological evolution during the early history of major groups, as lineages invade disparate ecological niches. However, few studies of adaptive radiation have included deep time data, so the links between extant diversity and major extinct radiations are unclear. The intensively studied Mesozoic dinosaur record provides a model system for such investigation, representing an ecologically diverse group that dominated terrestrial ecosystems for 170 million years. Furthermore, with 10,000 species, extant dinosaurs (birds) are the most speciose living tetrapod clade. We assembled composite trees of 614-622 Mesozoic dinosaurs/birds, and a comprehensive body mass dataset using the scaling relationship of limb bone robustness. Maximum-likelihood modelling and the node height test reveal rapid evolutionary rates and a predominance of rapid shifts among size classes in early (Triassic) dinosaurs. This indicates an early burst niche-filling pattern and contrasts with previous studies that favoured gradualistic rates. Subsequently, rates declined in most lineages, which rarely exploited new ecological niches. However, feathered maniraptoran dinosaurs (including Mesozoic birds) sustained rapid evolution from at least the Middle Jurassic, suggesting that these taxa evaded the effects of niche saturation. This indicates that a long evolutionary history of continuing ecological innovation paved the way for a second great radiation of dinosaurs, in birds. We therefore demonstrate links between the predominantly extinct deep time adaptive radiation of non-avian dinosaurs and the phenomenal diversification of birds, via continuing rapid rates of evolution along the phylogenetic stem lineage. This raises the possibility that the uneven distribution of biodiversity results not just from large-scale extrapolation of the process of adaptive radiation in a few extant clades, but also from the maintenance of evolvability on vast time scales across the history of life, in key lineages. PMID:24802911

Benson, Roger B J; Campione, Nicolás E; Carrano, Matthew T; Mannion, Philip D; Sullivan, Corwin; Upchurch, Paul; Evans, David C

2014-05-01

4

Dinosaurs.  

ERIC Educational Resources Information Center

Facts, activities, and student worksheets about dinosaurs are presented. General information about dinosaurs (when they lived and what they were like) and fossils (how they are created and what information they can provide) is followed by a worksheet and answer sheet. A timeline of the dinosaur age and a classification chart which divides…

Miller, Vicki; Happel, Sue

5

Matrix Elasticity Directs Stem Cell Lineage Specification  

Microsoft Academic Search

SUMMARY Microenvironments appear important in stem cell lineage specification but can be difficult to adequately characterize or control with soft tis- sues. Naive mesenchymal stem cells (MSCs) areshownheretospecifylineageandcommitto phenotypes with extreme sensitivity to tissue- level elasticity. Soft matrices that mimic brain are neurogenic, stiffer matricesthat mimicmus- cle are myogenic, and comparatively rigid matrices that mimic collagenous bone prove osteogenic. During

Adam J. Engler; Shamik Sen; H. Lee Sweeney; Dennis E. Discher

2006-01-01

6

Dinosaurs  

NSDL National Science Digital Library

This project was created to use with a first grade class. Most of the content will be used whole group on the Smartboard. WHOLE GROUP Life Has a History - Interactive slide show about diversity of animals, extinction, etc. Palenontology Portal FUN AND GAMES Build a Beast - Put bones together to make a skeleton of a prehistoric animal Build a Dinosaur - choose body parts and make a dinosaur Exploring Fossils and the Fossil Record Hide a beast - camouflage Dino Dig - Virtual dig for dinosaur bones that includes reconstruction of the skeleton ...

Stearns, Ms.

2008-10-26

7

Matrix elasticity directs stem cell lineage specification  

NASA Astrophysics Data System (ADS)

Adhesion of stem cells - like most cells - is not just a membrane phenomenon. Most tissue cells need to adhere to a ``solid'' for viability, and over the last decade it has become increasingly clear that the physical ``elasticity'' of that solid is literally ``felt'' by cells. Here we show that Mesenchymal Stem Cells (MSCs) specify lineage and commit to phenotypes with extreme sensitivity to the elasticity typical of tissues [1]. In serum only media, soft matrices that mimic brain appear neurogenic, stiffer matrices that mimic muscle are myogenic, and comparatively rigid matrices that mimic collagenous bone prove osteogenic. Inhibition of nonmuscle myosin II activity blocks all elasticity directed lineage specification, which indicates that the cytoskeleton pulls on matrix through adhesive attachments. Results have significant implications for `therapeutic' stem cells and have motivated development of a proteomic-scale method to identify mechano-responsive protein structures [2] as well as deeper physical studies of matrix physics [3] and growth factor pathways [4]. [4pt] [1] A. Engler, et al. Matrix elasticity directs stem cell lineage specification. Cell (2006).[0pt] [2] C.P. Johnson, et al. Forced unfolding of proteins within cells. Science (2007).[0pt] [3] A.E.X. Brown, et al. Multiscale mechanics of fibrin polymer: Gel stretching with protein unfolding and loss of water. Science (2009).[0pt] [4] D.E. Discher, et al. Growth factors, matrices, and forces combine and control stem cells. Science (2009).

Discher, Dennis

2010-03-01

8

The Drosophila cyst stem cell lineage  

PubMed Central

In all animals, germline cells differentiate in intimate contact with somatic cells and interactions between germline and soma are particularly important for germline development and function. In the male gonad of Drosophila melanogaster, the developing germline cells are enclosed by somatic cyst cells. The cyst cells are derived from cyst stem cells (CySCs) of somatic origin and codifferentiate with the germline cells. The fast generation cycle and the genetic tractability of Drosophila has made the Drosophila testis an excellent model for studying both the roles of somatic cells in guiding germline development and the interdependence of two separate stem cell lineages. This review focuses on our current understanding of CySC specification, CySC self-renewing divisions, cyst cell differentiation, and soma-germline interactions. Many of the mechanisms guiding these processes in Drosophila testes are similarly essential for the development and function of tissues in other organisms, most importantly for gametogenesis in mammals. PMID:23087834

Zoller, Richard; Schulz, Cordula

2012-01-01

9

Dinosaurs  

NSDL National Science Digital Library

This is a four day lesson plan that high school students grade 10-12 in the Child Care course can use to evaluate and then create their own lesson plan. This lesson plan also includes an example field trip. It can also be used for the high school students to experience teaching the preschool school children a unit on dinosaurs. At the end of reviewing this lesson plan students will be able to identify the components of this lesson plan and identify which DAP learning experience was used in each activity. After analyzing this lesson plan and identifying all the parts students will then be able to create their own lesson plan , picking a theme of their own. If used for students to teach the unit to preschoolers they will be able to present the lesson plan with all requirements met, and then better understand them to then create their own. Dinosaurs NOTE: For students who may have a disability preventing them from typing their lesson plan you could use the following assistive technology which allows them to speak into the computer and the computer types it up for them. A great source for this is: Dragon naturally speaking. Also you could ...

Weaver, Mrs.

2009-11-02

10

Notch Promotes Neural Lineage Entry by Pluripotent Embryonic Stem Cells  

E-print Network

Notch Promotes Neural Lineage Entry by Pluripotent Embryonic Stem Cells Sally Lowell1* , Alexandra Benchoua1,2 , Barry Heavey1 , Austin G. Smith1,3* 1 Centre Development in Stem Cell Biology, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom

Paris-Sud XI, Université de

11

Cytoskeleton-based forecasting of stem cell lineage fates  

E-print Network

), quantitative features of actin fluororeporter shapes, intensities, textures, and spatial distribu- tions showed a similar divergence of lineage fates, but delayed beyond 48 h. In summary, this high-content. biomaterials differentiation imaging and modeling stem cells actin organization Stem cells exhibiting

Androulakis, Ioannis (Yannis)

12

Cytoskeleton-based forecasting of stem cell lineage fates  

PubMed Central

Stem cells that adopt distinct lineages cannot be distinguished based on traditional cell shape. This study reports that higher-order variations in cell shape and cytoskeletal organization that occur within hours of stimulation forecast the lineage commitment fates of human mesenchymal stem cells (hMSCs). The unique approach captures numerous early (24 h), quantitative features of actin fluororeporter shapes, intensities, textures, and spatial distributions (collectively termed morphometric descriptors). The large number of descriptors are reduced into “combinations” through which distinct subpopulations of cells featuring unique combinations are identified. We demonstrate that hMSCs cultured on fibronectin-treated glass substrates under environments permissive to bone lineage induction could be readily discerned within the first 24 h from those cultured in basal- or fat-inductive conditions by such cytoskeletal feature groupings. We extend the utility of this approach to forecast osteogenic stem cell lineage fates across a series of synthetic polymeric materials of diverse physicochemical properties. Within the first 24 h following stem cell seeding, we could successfully “profile” the substrate responsiveness prospectively in terms of the degree of bone versus nonbone predisposition. The morphometric methodology also provided insights into how substrates may modulate the pace of osteogenic lineage specification. Cells on glass substrates deficient in fibronectin showed a similar divergence of lineage fates, but delayed beyond 48 h. In summary, this high-content imaging and single cell modeling approach offers a framework to elucidate and manipulate determinants of stem cell behaviors, as well as to screen stem cell lineage modulating materials and environments. PMID:20080726

Treiser, Matthew D.; Yang, Eric H.; Gordonov, Simon; Cohen, Daniel M.; Androulakis, Ioannis P.; Kohn, Joachim; Chen, Christopher S.; Moghe, Prabhas V.

2010-01-01

13

Generation of the epicardial lineage from human pluripotent stem cells.  

PubMed

The epicardium supports cardiomyocyte proliferation early in development and provides fibroblasts and vascular smooth muscle cells to the developing heart. The epicardium has been shown to play an important role during tissue remodeling after cardiac injury, making access to this cell lineage necessary for the study of regenerative medicine. Here we describe the generation of epicardial lineage cells from human pluripotent stem cells by stage-specific activation of the BMP and WNT signaling pathways. These cells display morphological characteristics and express markers of the epicardial lineage, including the transcription factors WT1 and TBX18 and the retinoic acid-producing enzyme ALDH1A2. When induced to undergo epithelial-to-mesenchymal transition, the cells give rise to populations that display characteristics of the fibroblast and vascular smooth muscle lineages. These findings identify BMP and WNT as key regulators of the epicardial lineage in vitro and provide a model for investigating epicardial function in human development and disease. PMID:25240927

Witty, Alec D; Mihic, Anton; Tam, Roger Y; Fisher, Stephanie A; Mikryukov, Alexander; Shoichet, Molly S; Li, Ren-Ke; Kattman, Steven J; Keller, Gordon

2014-10-01

14

Stochastic dynamics of interacting haematopoietic stem cell niche lineages.  

PubMed

Since we still know very little about stem cells in their natural environment, it is useful to explore their dynamics through modelling and simulation, as well as experimentally. Most models of stem cell systems are based on deterministic differential equations that ignore the natural heterogeneity of stem cell populations. This is not appropriate at the level of individual cells and niches, when randomness is more likely to affect dynamics. In this paper, we introduce a fast stochastic method for simulating a metapopulation of stem cell niche lineages, that is, many sub-populations that together form a heterogeneous metapopulation, over time. By selecting the common limiting timestep, our method ensures that the entire metapopulation is simulated synchronously. This is important, as it allows us to introduce interactions between separate niche lineages, which would otherwise be impossible. We expand our method to enable the coupling of many lineages into niche groups, where differentiated cells are pooled within each niche group. Using this method, we explore the dynamics of the haematopoietic system from a demand control system perspective. We find that coupling together niche lineages allows the organism to regulate blood cell numbers as closely as possible to the homeostatic optimum. Furthermore, coupled lineages respond better than uncoupled ones to random perturbations, here the loss of some myeloid cells. This could imply that it is advantageous for an organism to connect together its niche lineages into groups. Our results suggest that a potential fruitful empirical direction will be to understand how stem cell descendants communicate with the niche and how cancer may arise as a result of a failure of such communication. PMID:25188267

Székely, Tamás; Burrage, Kevin; Mangel, Marc; Bonsall, Michael B

2014-09-01

15

Lineage Tracing of Tissue-Specific Stem Cells In Vivo  

Microsoft Academic Search

\\u000a Tissue-specific stem cells are characterized by their ability to undergo unlimited self-renewal and generate transit-amplifying\\u000a progeny that yields all specialized cell types of a tissue. Both identification of stem cells and characterization of their\\u000a properties have been possible through the use of a range of methods to track cell fate in vivo or in vitro. In vivo systems\\u000a for lineage

Kurtis T. Sobush; Keitaro Matsumoto; Huaiyong Chen; Barry R. Stripp

16

Trophoblast lineage cells derived from human induced pluripotent stem cells  

PubMed Central

Background During implantation the blastocyst trophectoderm attaches to the endometrial epithelium and continues to differentiate into all trophoblast subtypes, which are the major components of a placenta. Aberrant trophoblast proliferation and differentiation are associated with placental diseases. However, due to ethical and practical issues, there is almost no available cell or tissue source to study the molecular mechanism of human trophoblast differentiation, which further becomes a barrier to the study of the pathogenesis of trophoblast-associated diseases of pregnancy. In this study, our goal was to generate a proof-of-concept model for deriving trophoblast lineage cells from induced pluripotency stem (iPS) cells from human fibroblasts. In future studies the generation of trophoblast lineage cells from iPS cells established from patient’s placenta will be extremely useful for studying the pathogenesis of individual trophoblast-associated diseases and for drug testing. Methods and Results Combining iPS cell technology with BMP4 induction, we derived trophoblast lineage cells from human iPS cells. The gene expression profile of these trophoblast lineage cells was distinct from fibroblasts and iPS cells. These cells expressed markers of human trophoblasts. Furthermore, when these cells were differentiated they exhibited invasive capacity and placental hormone secretive capacity, suggesting extravillous trophoblasts and syncytiotrophoblasts. Conclusion Trophoblast lineage cells can be successfully derived from human iPS cells, which provide a proof-of-concept tool to recapitulate pathogenesis of patient placental trophoblasts in vitro. PMID:23774580

Chen, Ying; Wang, Kai; Chandramouli, Gadisetti V.R.; Knott, Jason G.; Leach, Richard

2013-01-01

17

Trophoblast lineage cells derived from human induced pluripotent stem cells  

SciTech Connect

Highlights: •Epithelial-like phenotype of trophoblast lineage cells derived from human iPS cells. •Trophoblast lineage cells derived from human iPS cells exhibit trophoblast function. •Trophoblasts from iPS cells provides a proof-of-concept in regenerative medicine. -- Abstract: Background: During implantation, the blastocyst trophectoderm attaches to the endometrial epithelium and continues to differentiate into all trophoblast subtypes, which are the major components of a placenta. Aberrant trophoblast proliferation and differentiation are associated with placental diseases. However, due to ethical and practical issues, there is almost no available cell or tissue source to study the molecular mechanism of human trophoblast differentiation, which further becomes a barrier to the study of the pathogenesis of trophoblast-associated diseases of pregnancy. In this study, our goal was to generate a proof-of-concept model for deriving trophoblast lineage cells from induced pluripotency stem (iPS) cells from human fibroblasts. In future studies the generation of trophoblast lineage cells from iPS cells established from patient’s placenta will be extremely useful for studying the pathogenesis of individual trophoblast-associated diseases and for drug testing. Methods and results: Combining iPS cell technology with BMP4 induction, we derived trophoblast lineage cells from human iPS cells. The gene expression profile of these trophoblast lineage cells was distinct from fibroblasts and iPS cells. These cells expressed markers of human trophoblasts. Furthermore, when these cells were differentiated they exhibited invasive capacity and placental hormone secretive capacity, suggesting extravillous trophoblasts and syncytiotrophoblasts. Conclusion: Trophoblast lineage cells can be successfully derived from human iPS cells, which provide a proof-of-concept tool to recapitulate pathogenesis of patient placental trophoblasts in vitro.

Chen, Ying, E-mail: ying.chen@hc.msu.edu [Department of Obstetrics, Gynecology and Reproductive Biology, Michigan State University, 333 Bostwick NE, Grand Rapids, MI 49503 (United States)] [Department of Obstetrics, Gynecology and Reproductive Biology, Michigan State University, 333 Bostwick NE, Grand Rapids, MI 49503 (United States); Wang, Kai; Chandramouli, Gadisetti V.R. [Department of Obstetrics, Gynecology and Reproductive Biology, Michigan State University, 333 Bostwick NE, Grand Rapids, MI 49503 (United States)] [Department of Obstetrics, Gynecology and Reproductive Biology, Michigan State University, 333 Bostwick NE, Grand Rapids, MI 49503 (United States); Knott, Jason G. [Developmental Epigenetics Laboratory, Department of Animal Science, Michigan State University (United States)] [Developmental Epigenetics Laboratory, Department of Animal Science, Michigan State University (United States); Leach, Richard, E-mail: Richard.leach@hc.msu.edu [Department of Obstetrics, Gynecology and Reproductive Biology, Michigan State University, 333 Bostwick NE, Grand Rapids, MI 49503 (United States) [Department of Obstetrics, Gynecology and Reproductive Biology, Michigan State University, 333 Bostwick NE, Grand Rapids, MI 49503 (United States); Department of Obstetrics, Gynecology and Women’s Health, Spectrum Health Medical Group (United States)

2013-07-12

18

Role of biomechanical forces in stem cell vascular lineage differentiation.  

PubMed

Mechanical forces have long been known to play a role in the maintenance of vascular homeostasis in the mature animal and in developmental regulation in the fetus. More recently, it has been shown that stem cells play a role in vascular repair and remodeling in response to biomechanical stress. Laminar shear stress can directly activate growth factor receptors on stem/progenitor cells, initiating signaling pathways leading toward endothelial cell differentiation. Cyclic strain can stimulate stem cell differentiation toward smooth muscle lineages through different mechanisms. In vivo, blood flow in the coronary artery is significantly altered after stenting, leading to changes in biomechanical forces on the vessel wall. This disruption may activate stem cell differentiation into a variety of cells and cause delayed re-endothelialization. Based on progress in the research field, the present review aims to explore the role of mechanical forces in stem cell differentiation both in vivo and in vitro and to examine what this means for the application of stem cells in the clinic, in tissue engineering, and for the management of aberrant stem cell contribution to disease. PMID:25012135

Potter, Claire M F; Lao, Ka Hou; Zeng, Lingfang; Xu, Qingbo

2014-10-01

19

Mixed lineage leukemia protein in normal and leukemic stem cells.  

PubMed

Transcription factors critical for normal hematopoietic stem cell functions are frequently mutated in acute leukemia leading to an aberrant re-programming of normal hematopoietic progenitor/stem cells into leukemic stem cells. Among them, re-arrangements of the mixed lineage leukemia gene (MLL), including chimeric fusion, partial tandem duplication (PTD), amplification and internal exonic deletion, represent one of the most common recurring oncogenic events and associate with very poor prognosis in human leukemias. Extensive research on wild type MLL and MLL-fusions has significant advanced our knowledge about their functions in normal and malignant hematopoiesis, which also provides a framework for the underlying pathogenic role of MLL re-arrangements in human leukemias. In contrast, research progress on MLL-PTD, MLL amplification and internal exonic deletion remains stagnant, in particular for the last two abnormalities where mouse model is not yet available. In this article, we will review the key features of both wild-type and re-arranged MLL proteins with particular focuses on MLL-PTD and MLL amplification for their roles in normal and malignant hematopoiesis. PMID:23598978

Yip, Bon Ham; So, Chi Wai Eric

2013-03-01

20

Concise Review: Chemical Approaches for Modulating Lineage-Specific Stem Cells and Progenitors  

PubMed Central

Generation and manipulation of lineage-restricted stem and progenitor cells in vitro and/or in vivo are critical for the development of stem cell-based clinical therapeutics. Lineage-restricted stem and progenitor cells have many advantageous qualities, including being able to efficiently engraft and differentiate into desirable cell types in vivo after transplantation, and they are much less tumorigenic than pluripotent cells. Generation of lineage-restricted stem and progenitor cells can be achieved by directed differentiation from pluripotent stem cells or lineage conversion from easily obtained somatic cells. Small molecules can be very helpful in these processes since they offer several important benefits. For example, the risk of tumorigenesis is greatly reduced when small molecules are used to replace integrated transcription factors, which are widely used in cell fate conversion. Furthermore, small molecules are relatively easy to apply, optimize, and manufacture, and they can more readily be developed into conventional pharmaceuticals. Alternatively, small molecules can be used to expand or selectively control the differentiation of lineage-restricted stem and progenitor cells for desirable therapeutics purposes in vitro or in vivo. Here we summarize recent progress in the use of small molecules for the expansion and generation of desirable lineage-restricted stem and progenitor cells in vitro and for selectively controlling cell fate of lineage-restricted stem and progenitor cells in vivo, thereby facilitating stem cell-based clinical applications. PMID:23580542

Xu, Tao; Zhang, Mingliang; Laurent, Timothy; Xie, Min

2013-01-01

21

The neural stem cell lineage reveals novel relationships among spermatogonial germ stem cells and other pluripotent stem cells.  

PubMed

The embryonic stem cell (ESC) derived from the inner cell mass is viewed as the core pluripotent cell (PC) type from which all other cell types emanate. This familiar perspective derives from an embryological time line in which PCs are ordered according to their time of appearance. However, this schema does not take into account their potential for interconversion, thereby excluding this critical quality of PCs. The persistence of bona fide pluripotent adult stem cells has garnered increasing attention in recent years. Adult pluripotent spermatogonial germ stem cells (aSGSCs) arise from primordial germ cells (pGCs) that emerge from the epiblast during gastrulation. Adult definitive neural stem cells (dNSCs) arise clonally from pluripotent embryonic primitive neural stem cells (pNSCs), which can also be derived clonally from ESCs. To test for stem cell-type convertibility, we employed differentiation in the clonal lineage from ESCs to pNSCs to dNSCs, and revealed the relationships and lineage positioning among various PC populations, including spermatogonial germ cells (aSGSCs), epiblast-derived stem cells (Epi-SCs) and the bFGF, Activin, and BIO-derived stem cell (FAB-SC). Adult, murine aSGSCs assumed a 'pseudo-ESC' state in vitro, and then differentiated into dNSCs, but not pNSCs. Similarly, Epi-SCs and FAB-SCs only gave rise to dNSCs and not to pNSCs. The results of these experiments suggest a new pluripotency lineage model describing the relationship(s) among PCs that better reflects the transitions between these cell types in vitro. PMID:24192139

Teichert, Anouk-Martine; Pereira, Schreiber; Coles, Brenda; Chaddah, Radha; Runciman, Susan; Brokhman, Irina; van der Kooy, Derek

2014-04-01

22

TISSUE-SPECIFIC STEM CELLS Rho GTPases Mediate the Mechanosensitive Lineage Commitment of  

E-print Network

mechanotransduction · Rho GTP-binding proteins · Adipose stem cells · Extracellular matrix · Elastic modulus ABSTRACTTISSUE-SPECIFIC STEM CELLS Rho GTPases Mediate the Mechanosensitive Lineage Commitment of Neural Stem Cells ALBERT J. KEUNG,a ELENA M. DE JUAN-PARDO,b,c DAVID V. SCHAFFER,a,b,d SANJAY KUMAR b

Kumar, Sanjay

23

Human amniotic fluid stem cell differentiation along smooth muscle lineage.  

PubMed

Functional smooth muscle engineering requires isolation and expansion of smooth muscle cells (SMCs), and this process is particularly challenging for visceral smooth muscle tissue where progenitor cells have not been clearly identified. Herein we showed for the first time that efficient SMCs can be obtained from human amniotic fluid stem cells (hAFSCs). Clonal lines were generated from c-kit(+) hAFSCs. Differentiation toward SM lineage (SMhAFSCs) was obtained using a medium conditioned by PDGF-BB and TGF-?1. Molecular assays revealed higher level of ? smooth muscle actin (?-SMA), desmin, calponin, and smoothelin in SMhAFSCs when compared to hAFSCs. Ultrastructural analysis demonstrated that SMhAFSCs also presented in the cytoplasm increased intermediate filaments, dense bodies, and glycogen deposits like SMCs. SMhAFSC metabolism evaluated via mass spectrometry showed higher glucose oxidation and an enhanced response to mitogenic stimuli in comparison to hAFSCs. Patch clamp of transduced hAFSCs with lentiviral vectors encoding ZsGreen under the control of the ?-SMA promoter was performed demonstrating that SMhAFSCs retained a smooth muscle cell-like electrophysiological fingerprint. Eventually SMhAFSCs contractility was evident both at single cell level and on a collagen gel. In conclusion, we showed here that hAFSCs under selective culture conditions are able to give rise to functional SMCs. PMID:23995291

Ghionzoli, Marco; Repele, Andrea; Sartiani, Laura; Costanzi, Giulia; Parenti, Astrid; Spinelli, Valentina; David, Anna L; Garriboli, Massimo; Totonelli, Giorgia; Tian, Jun; Andreadis, Stelios T; Cerbai, Elisabetta; Mugelli, Alessandro; Messineo, Antonio; Pierro, Agostino; Eaton, Simon; De Coppi, Paolo

2013-12-01

24

Differentiation of murine embryonic stem and induced pluripotent stem cells to renal lineage in vitro  

SciTech Connect

Embryonic stem (ES) cells which have the unlimited proliferative capacity and extensive differentiation potency can be an attractive source for kidney regeneration therapies. Recent breakthroughs in the generation of induced pluripotent stem (iPS) cells have provided with another potential source for the artificially-generated kidney. The purpose of this study is to know how to differentiate mouse ES and iPS cells into renal lineage. We used iPS cells from mouse fibroblasts by transfection of four transcription factors, namely Oct4, Sox2, c-Myc and Klf4. Real-time PCR showed that renal lineage markers were expressed in both ES and iPS cells after the induction of differentiation. It also showed that a tubular specific marker, KSP progressively increased to day 18, although the differentiation of iPS cells was slower than ES cells. The results indicated that renal lineage cells can be differentiated from both murine ES and iPS cells. Several inducing factors were tested whether they influenced on cell differentiation. In ES cells, both of GDNF and BMP7 enhanced the differentiation to metanephric mesenchyme, and Activin enhanced the differentiation of ES cells to tubular cells. Activin also enhanced the differentiation of iPS cells to tubular cells, although the enhancement was lower than in ES cells. ES and iPS cells have a potential to differentiate to renal lineage cells, and they will be an attractive resource of kidney regeneration therapy. This differentiation is enhanced by Activin in both ES and iPS cells.

Morizane, Ryuji [Department of Internal Medicine, Keio University School of Medicine, Tokyo (Japan)] [Department of Internal Medicine, Keio University School of Medicine, Tokyo (Japan); Monkawa, Toshiaki, E-mail: monkawa@sc.itc.keio.ac.jp [Department of Internal Medicine, Keio University School of Medicine, Tokyo (Japan)] [Department of Internal Medicine, Keio University School of Medicine, Tokyo (Japan); Itoh, Hiroshi [Department of Internal Medicine, Keio University School of Medicine, Tokyo (Japan)] [Department of Internal Medicine, Keio University School of Medicine, Tokyo (Japan)

2009-12-25

25

Researcharticle Molecular Signatures of the Three Stem Cell Lineages in  

E-print Network

the evolution of stem cells requires molecular profiling of stem cells in an animal at a basal phylogenetic in metazoan evolution. They are corroborating the view that stem cell types shared common, multifunctional: aging, adult stem cell, self-renewal, differentiation, evolution. Introduction The evolution

26

Telomerase protects werner syndrome lineage-specific stem cells from premature aging.  

PubMed

Werner syndrome (WS) patients exhibit premature aging predominantly in mesenchyme-derived tissues, but not in neural lineages, a consequence of telomere dysfunction and accelerated senescence. The cause of this lineage-specific aging remains unknown. Here, we document that reprogramming of WS fibroblasts to pluripotency elongated telomere length and prevented telomere dysfunction. To obtain mechanistic insight into the origin of tissue-specific aging, we differentiated iPSCs to mesenchymal stem cells (MSCs) and neural stem/progenitor cells (NPCs). We observed recurrence of premature senescence associated with accelerated telomere attrition and defective synthesis of the lagging strand telomeres in MSCs, but not in NPCs. We postulate this "aging" discrepancy is regulated by telomerase. Expression of hTERT or p53 knockdown ameliorated the accelerated aging phenotypein MSC, whereas inhibition of telomerase sensitized NPCs to DNA damage. Our findings unveil a role for telomerase in the protection of accelerated aging in a specific lineage of stem cells. PMID:24749076

Cheung, Hoi-Hung; Liu, Xiaozhuo; Canterel-Thouennon, Lucile; Li, Lu; Edmonson, Catherine; Rennert, Owen M

2014-04-01

27

Telomerase Protects Werner Syndrome Lineage-Specific Stem Cells from Premature Aging  

PubMed Central

Summary Werner syndrome (WS) patients exhibit premature aging predominantly in mesenchyme-derived tissues, but not in neural lineages, a consequence of telomere dysfunction and accelerated senescence. The cause of this lineage-specific aging remains unknown. Here, we document that reprogramming of WS fibroblasts to pluripotency elongated telomere length and prevented telomere dysfunction. To obtain mechanistic insight into the origin of tissue-specific aging, we differentiated iPSCs to mesenchymal stem cells (MSCs) and neural stem/progenitor cells (NPCs). We observed recurrence of premature senescence associated with accelerated telomere attrition and defective synthesis of the lagging strand telomeres in MSCs, but not in NPCs. We postulate this “aging” discrepancy is regulated by telomerase. Expression of hTERT or p53 knockdown ameliorated the accelerated aging phenotypein MSC, whereas inhibition of telomerase sensitized NPCs to DNA damage. Our findings unveil a role for telomerase in the protection of accelerated aging in a specific lineage of stem cells. PMID:24749076

Cheung, Hoi-Hung; Liu, Xiaozhuo; Canterel-Thouennon, Lucile; Li, Lu; Edmonson, Catherine; Rennert, Owen M.

2014-01-01

28

Notch1 activation increases hematopoietic stem cell self-renewal in vivo and favors lymphoid over myeloid lineage outcome.  

PubMed

Hematopoietic stem cells sequentially pass through a series of decision points affecting self-renewal or lineage-specific differentiation. Notch1 receptor is a known modulator of lineage-specific events in hematopoiesis that we assessed in the context of in vivo stem cell kinetics. Using RAG-1(-/-) mouse stems cells, we documented increased stem cell numbers due to decreased differentiation and enhanced stem cell self-renewal induced by Notch1. Unexpectedly, preferential lymphoid over myeloid lineage commitment was noted when differentiation occurred. Therefore, Notch1 affects 2 decision points in stem cell regulation, favoring self-renewal over differentiation and lymphoid over myeloid lineage outcome. Notch1 offers an attractive target for stem cell manipulation strategies, particularly in the context of immunodeficiency and acquired immunodeficiency syndrome. PMID:11895769

Stier, Sebastian; Cheng, Tao; Dombkowski, David; Carlesso, Nadia; Scadden, David T

2002-04-01

29

Vertebrate Neural Stem Cell Segmentation, Tracking and Lineaging with Validation and Editing  

PubMed Central

This protocol and the accompanying software program called LEVER enable quantitative automated analysis of phase contrast time-lapse images of cultured neural stem cells. Images are captured at 5 min. intervals over a period of 5 to 15 days as the cells proliferate and differentiate. LEVER automatically segments, tracks and generates lineage trees of the stem cells from the image sequence. In addition to generating lineage trees capturing the population dynamics of clonal development, LEVER extracts quantitative phenotypic measurements of cell location, shape, movement, and size. When available, the system can include biomolecular markers imaged using fluorescence. It then displays the results to the user for highly efficient inspection and editing to correct any errors in the segmentation, tracking or lineaging. In order to enable high-throughput inspection, LEVER incorporates features for rapid identification of errors, and learning from user-supplied corrections to automatically identify and correct related errors. PMID:22094730

Winter, Mark; Wait, Eric; Roysam, Badri; Goderie, Susan; Ali, Rania Ahmed Naguib; Kokovay, Erzsebet; Temple, Sally; Cohen, Andrew R.

2012-01-01

30

Fetal and Adult Hematopoietic Stem Cells Give Rise to Distinct T Cell Lineages in Humans  

Microsoft Academic Search

Although the mammalian immune system is generally thought to develop in a linear fashion, findings in avian and murine species argue instead for the developmentally ordered appearance (or ``layering'') of distinct hematopoietic stem cells (HSCs) that give rise to distinct lymphocyte lineages at different stages of development. Here we provide evidence of an analogous layered immune system in humans. Our

Jeff E. Mold; Shivkumar Venkatasubrahmanyam; Trevor D. Burt; Jakob Michaëlsson; Jose M. Rivera; Sofiya A. Galkina; Kenneth Weinberg; Cheryl A. Stoddart; Joseph M. McCune

2010-01-01

31

Dinosaur Names  

NSDL National Science Digital Library

In this classroom activity, young students explore the meaning behind dinosaurs' names. The activity opens with background information for teachers about the Greek and Latin root words that are used in dinosaur names. After discussing what they know about dinosaurs, students learn that dinosaur names can describe what the dinosaur looked like, how it might have acted, or where it was found. Working as a class, students use a chart of root words and their meanings to decipher the names of four well-known dinosaurs.

32

Different roles of TGF-? in the multi-lineage differentiation of stem cells.  

PubMed

Stem cells are a population of cells that has infinite or long-term self-renewal ability and can produce various kinds of descendent cells. Transforming growth factor ? (TGF-?) family is a superfamily of growth factors, including TGF-?1, TGF-?2 and TGF-?3, bone morphogenetic proteins, activin/inhibin, and some other cytokines such as nodal, which plays very important roles in regulating a wide variety of biological processes, such as cell growth, differentiation, cell death. TGF-?, a pleiotropic cytokine, has been proved to be differentially involved in the regulation of multi-lineage differentiation of stem cells, through the Smad pathway, non-Smad pathways including mitogen-activated protein kinase pathways, phosphatidylinositol-3-kinase/AKT pathways and Rho-like GTPase signaling pathways, and their cross-talks. For instance, it is generally known that TGF-? promotes the differentiation of stem cells into smooth muscle cells, immature cardiomyocytes, chondrocytes, neurocytes, hepatic stellate cells, Th17 cells, and dendritic cells. However, TGF-? inhibits the differentiation of stem cells into myotubes, adipocytes, endothelial cells, and natural killer cells. Additionally, TGF-? can provide competence for early stages of osteoblastic differentiation, but at late stages TGF-? acts as an inhibitor. The three mammalian isoforms (TGF-?1, 2 and 3) have distinct but overlapping effects on hematopoiesis. Understanding the mechanisms underlying the regulatory effect of TGF-? in the stem cell multi-lineage differentiation is of importance in stem cell biology, and will facilitate both basic research and clinical applications of stem cells. In this article, we discuss the current status and progress in our understanding of different mechanisms by which TGF-? controls multi-lineage differentiation of stem cells. PMID:22993659

Wang, Ming-Ke; Sun, Hui-Qin; Xiang, Ying-Chun; Jiang, Fan; Su, Yong-Ping; Zou, Zhong-Min

2012-05-26

33

Rewiring mesenchymal stem cell lineage specification by switching the biophysical microenvironment  

NASA Astrophysics Data System (ADS)

The propensity of stem cells to specify and commit to a particular lineage program is guided by dynamic biophysical and biochemical signals that are temporally regulated. However, most in vitro studies rely on ``snapshots'' of cell state under static conditions. Here we asked whether changing the biophysical aspects of the substrate could modulate the degree of mesenchymal stem cell (MSC) lineage specification. We chose to explore two diverse differentiation outcomes: MSC osteogenesis and trans-differentiation to neuron-like cells. MSCs were cultured on soft (~0.5 kPa) or stiff (~40 kPa) hydrogels followed by transfer to gels of the opposite stiffness. MSCs on soft gels express elevated neurogenesis markers while MSCs on stiff substrates express elevated osteogenesis markers. Transfer of MSCs from soft to stiff or stiff to soft substrates led to a switch in lineage specification. However, MSCs transferred from stiff to soft substrates maintained elevated osteogenesis markers, suggesting a degree of irreversible activation. Transferring MSCs to micropatterned substrates reveal geometric cues that further modulate lineage reversal. Taken together, this study demonstrates that MSCs remain susceptible to the biophysical properties of the extracellular matrix--even after several weeks of culture--and can redirect lineage specification in response to changes in the microenvironment.

Lee, Junmin; Abdeen, Amr A.; Kilian, Kristopher A.

2014-06-01

34

Rewiring mesenchymal stem cell lineage specification by switching the biophysical microenvironment.  

PubMed

The propensity of stem cells to specify and commit to a particular lineage program is guided by dynamic biophysical and biochemical signals that are temporally regulated. However, most in vitro studies rely on "snapshots" of cell state under static conditions. Here we asked whether changing the biophysical aspects of the substrate could modulate the degree of mesenchymal stem cell (MSC) lineage specification. We chose to explore two diverse differentiation outcomes: MSC osteogenesis and trans-differentiation to neuron-like cells. MSCs were cultured on soft (~0.5?kPa) or stiff (~40?kPa) hydrogels followed by transfer to gels of the opposite stiffness. MSCs on soft gels express elevated neurogenesis markers while MSCs on stiff substrates express elevated osteogenesis markers. Transfer of MSCs from soft to stiff or stiff to soft substrates led to a switch in lineage specification. However, MSCs transferred from stiff to soft substrates maintained elevated osteogenesis markers, suggesting a degree of irreversible activation. Transferring MSCs to micropatterned substrates reveal geometric cues that further modulate lineage reversal. Taken together, this study demonstrates that MSCs remain susceptible to the biophysical properties of the extracellular matrix--even after several weeks of culture--and can redirect lineage specification in response to changes in the microenvironment. PMID:24898422

Lee, Junmin; Abdeen, Amr A; Kilian, Kristopher A

2014-01-01

35

Polycomb Repressive Complex 2 Regulates Lineage Fidelity during Embryonic Stem Cell Differentiation  

PubMed Central

Polycomb Repressive Complex 2 (PRC2) catalyzes histone H3 lysine 27 tri-methylation (H3K27me3), an epigenetic modification associated with gene repression. H3K27me3 is enriched at the promoters of a large cohort of developmental genes in embryonic stem cells (ESCs). Loss of H3K27me3 leads to a failure of ESCs to properly differentiate, making it difficult to determine the precise roles of PRC2 during lineage commitment. Moreover, while studies suggest that PRC2 prevents DNA methylation, how these two epigenetic regulators coordinate to regulate lineage programs is poorly understood. Using several PRC2 mutant ESC lines that maintain varying levels of H3K27me3, we found that partial maintenance of H3K27me3 allowed for proper temporal activation of lineage genes during directed differentiation of ESCs to spinal motor neurons (SMNs). In contrast, genes that function to specify other lineages failed to be repressed in these cells, suggesting that PRC2 is also necessary for lineage fidelity. We also found that loss of H3K27me3 leads to a modest gain in DNA methylation at PRC2 target regions in both ESCs and in SMNs. Our study demonstrates a critical role for PRC2 in safeguarding lineage decisions and in protecting genes against inappropriate DNA methylation. PMID:25333635

Thornton, Seraphim R.; Butty, Vincent L.; Levine, Stuart S.; Boyer, Laurie A.

2014-01-01

36

Stretch-activated ion channel Piezo1 directs lineage choice in human neural stem cells.  

PubMed

Neural stem cells are multipotent cells with the ability to differentiate into neurons, astrocytes, and oligodendrocytes. Lineage specification is strongly sensitive to the mechanical properties of the cellular environment. However, molecular pathways transducing matrix mechanical cues to intracellular signaling pathways linked to lineage specification remain unclear. We found that the mechanically gated ion channel Piezo1 is expressed by brain-derived human neural stem/progenitor cells and is responsible for a mechanically induced ionic current. Piezo1 activity triggered by traction forces elicited influx of Ca(2+), a known modulator of differentiation, in a substrate-stiffness-dependent manner. Inhibition of channel activity by the pharmacological inhibitor GsMTx-4 or by siRNA-mediated Piezo1 knockdown suppressed neurogenesis and enhanced astrogenesis. Piezo1 knockdown also reduced the nuclear localization of the mechanoreactive transcriptional coactivator Yes-associated protein. We propose that the mechanically gated ion channel Piezo1 is an important determinant of mechanosensitive lineage choice in neural stem cells and may play similar roles in other multipotent stem cells. PMID:25349416

Pathak, Medha M; Nourse, Jamison L; Tran, Truc; Hwe, Jennifer; Arulmoli, Janahan; Le, Dai Trang T; Bernardis, Elena; Flanagan, Lisa A; Tombola, Francesco

2014-11-11

37

Zoom Dinosaurs  

NSDL National Science Digital Library

Zoom Dinosaurs is a comprehensive on-line hypertext book about dinosaurs. It is designed for students of all ages and levels of comprehension. An easy-to-use structure allows readers to start at a basic level on each topic, then progress to more advanced information as desired simply by clicking on links. The site contains handouts, dinosaur myths, etymologies, evolution, coloring pages, non-dinosaur creatures, activities, and links for more information. Each dinosaur page contains information on size, anatomy, body features, behavior, life span, diet, intelligence, classification, discovery of its fossils, and a diagram.

38

Dinosaur Illustrations  

NSDL National Science Digital Library

Are you searching for images of dinosaurs? If so, then set your sights on David Goldman's website of dinosaur illustrations. Mr. Goldman, a dinosaur aficionado, has created a nicely organized site connecting visitors to an impressive online network of dinosaur artwork. The website hosts a diverse and extensive collection of dinosaurs including the Allosaurus, Hadrosaur, Oviraptor, Pteranodon, and over course the iconic Tyrannosaurus Rex. Dinosaur illustrations can be located by alphabetic index, or by using the site's search engine. Illustration listings are accompanied by small, hyperlinked preview images that connect to the illustration's Internet source. The website also links to a collection of Panoramas, prehistoric animal images, and paleontology book reviews appearing in _Prehistoric Times_.

39

Dinosaur Paleontology  

NSDL National Science Digital Library

Until recently, dinosaurs were looked upon as sluggish, dim-witted beasts dragging their tails in the swamps. With the commercialization of Jurassic Park, students today have a different view of dinosaur life, but what they may not understand is the process used by scientists to revise their interpretation of the fossil record. The purpose of this unit is to have students understand how the scientific method is used to study the life history of dinosaurs. Using readings, video productions, and resources available from museums of paleontology, students are challenged to think of how we can best interpret the fossil record as it pertains to dinosaurs. Students investigate themes in dinosaur evolution, anatomy, physiology, and behavior, as well as ideas regarding the formulation of their own hypotheses pertaining to dinosaur life, and they are further challenged to describe the ways in which they would obtain evidence to support their ideas.

BEGIN:VCARD VERSION:2.1 FN:Mark Stefanski N:Stefanski;Mark ORG:Marin Academy REV:2005-04-14 END:VCARD

1995-06-30

40

Feathered Dinosaur  

NSDL National Science Digital Library

This American Museum of Natural History press release, issued in April 2001, announces the discovery of a remarkably well-preserved, 130-million-year-old fossil dinosaur covered from head to tail with downy fluff and primitive feathers. The press release includes details about where the dinosaur was unearthed, and by whom, the significance of the finding, the geologic reasons why the area where this specimen was found has been a treasure trove of fossils and how dinosaurs are related to birds.

41

Dinosaur Eggs  

NSDL National Science Digital Library

This National Geographic Society (NGS) website takes users behind the scenes of their 1996 article 'The Great Dinosaur Egg Hunt'. The site contains an online egg hunt and a look at fossil researchers as they 'hatch' fossilized dinosaur eggs to reveal the embryos inside. This includes an in-depth look at 3 different dinosaur eggs that have been found, how researchers view the insides of fossilized eggs, the process of embryo modeling, and virtual reality views of hatchlings and embryos.

Anderson, Carolyn

42

Dinosaur evolution. Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds.  

PubMed

Recent discoveries have highlighted the dramatic evolutionary transformation of massive, ground-dwelling theropod dinosaurs into light, volant birds. Here, we apply Bayesian approaches (originally developed for inferring geographic spread and rates of molecular evolution in viruses) in a different context: to infer size changes and rates of anatomical innovation (across up to 1549 skeletal characters) in fossils. These approaches identify two drivers underlying the dinosaur-bird transition. The theropod lineage directly ancestral to birds undergoes sustained miniaturization across 50 million years and at least 12 consecutive branches (internodes) and evolves skeletal adaptations four times faster than other dinosaurs. The distinct, prolonged phase of miniaturization along the bird stem would have facilitated the evolution of many novelties associated with small body size, such as reorientation of body mass, increased aerial ability, and paedomorphic skulls with reduced snouts but enlarged eyes and brains. PMID:25082702

Lee, Michael S Y; Cau, Andrea; Naish, Darren; Dyke, Gareth J

2014-08-01

43

Genetic regulatory networks programming hematopoietic stem cells and erythroid lineage specification.  

PubMed

Erythroid cell production results from passage through cellular hierarchies dependent on differential gene expression under the control of transcription factors responsive to changing niches. We have constructed Genetic Regulatory Networks (GRNs) describing this process, based predominantly on mouse data. Regulatory network motifs identified in E. coli and yeast GRNs are found in combination in these GRNs. Feed-forward motifs with autoregulation generate forward momentum and also control its rate, which is at its lowest in hematopoietic stem cells (HSCs). The simultaneous requirement for multiple regulators in multi-input motifs (MIMs) provides tight control over expression of target genes. Combinations of MIMs, exemplified by the SCL/LMO2 complexes, which have variable content and binding sites, explain how individual regulators can have different targets in HSCs and erythroid cells and possibly also how HSCs maintain stem cell functions while expressing lineage-affiliated genes at low level, so-called multi-lineage priming. MIMs combined with cross-antagonism describe the relationship between PU.1 and GATA-1 and between two of their target genes, Fli-1 and EKLF, with victory for GATA-1 and EKLF leading to erythroid lineage specification. These GRNs are useful repositories for current regulatory information, are accessible in interactive form via the internet, enable the consequences of perturbation to be predicted, and can act as seed networks to organize the rapidly accumulating microarray data. PMID:16626682

Swiers, Gemma; Patient, Roger; Loose, Matthew

2006-06-15

44

Activation of the amino acid response modulates lineage specification during differentiation of murine embryonic stem cells  

PubMed Central

In somatic cells, a collection of signaling pathways activated by amino acid limitation have been identified and referred to as the amino acid response (AAR). Despite the importance of possible detrimental effects of nutrient limitation during in vitro culture, the AAR has not been investigated in embryonic stem cells (ESC). AAR activation caused the expected increase in transcription factors that mediate specific AAR pathways, as well as the induction of asparagine synthetase, a terminal AAR target gene. Neither AAR activation nor stable knockdown of activating transcription factor (Atf) 4, a transcriptional mediator of the AAR, adversely affected ESC self-renewal or pluripotency. Low-level induction of the AAR over a 12-day period of embryoid body differentiation did alter lineage specification such that the primitive endodermal, visceral endodermal, and endodermal lineages were favored, whereas mesodermal and certain ectodermal lineages were suppressed. Knockdown of Atf4 further enhanced the AAR-induced increase in endodermal formation, suggesting that this phenomenon is mediated by an Atf4-independent mechanism. Collectively, the results indicate that, during differentiation of mouse embryoid bodies in culture, the availability of nutrients, such as amino acids, can influence the formation of specific cell lineages. PMID:23736538

Shan, Jixiu; Hamazaki, Takashi; Tang, Tiffany A.; Terada, Naohiro

2013-01-01

45

Lineage Tracing of Pf4-Cre Marks Hematopoietic Stem Cells and Their Progeny  

PubMed Central

The development of a megakaryocyte lineage specific Cre deleter, using the Pf4 (CXCL4) promoter (Pf4-Cre), was a significant step forward in the specific analysis of platelet and megakaryocyte cell biology. However, in the present study we have employed a sensitive reporter-based approach to demonstrate that Pf4-Cre also recombines in a significant proportion of both fetal liver and bone marrow hematopoietic stem cells (HSCs), including the most primitive fraction containing the long-term repopulating HSCs. Consequently, we demonstrate that Pf4-Cre activity is not megakaryocyte lineage-specific but extends to other myeloid and lymphoid lineages at significant levels between 15–60%. Finally, we show for the first time that Pf4 transcripts are present in adult HSCs and primitive hematopoietic progenitor cells. These results have fundamental implications for the use of the Pf4-Cre mouse model and for our understanding of a possible role for Pf4 in the development of the hematopoietic lineage. PMID:23300543

Schachtner, Hannah; Watson, Steve P.; Holyoake, Tessa L.; Kranc, Kamil R.; Machesky, Laura M.

2012-01-01

46

Histone Deacetylase 1 and 3 Regulate the Mesodermal Lineage Commitment of Mouse Embryonic Stem Cells  

PubMed Central

The important role of histone acetylation alteration has become increasingly recognized in mesodermal lineage differentiation and development. However, the contribution of individual histone deacetylases (HDACs) to mesoderm specification remains poorly understood. In this report, we found that trichostatin A (TSA), an inhibitor of histone deacetylase (HDACi), could induce early differentiation of embryonic stem cells (ESCs) and promote mesodermal lineage differentiation. Further analysis showed that the expression levels of HDAC1 and 3 are decreased gradually during ESCs differentiation. Ectopic expression of HDAC1 or 3 significantly inhibited differentiation into the mesodermal lineage. By contrast, loss of either HDAC1 or 3 enhanced the mesodermal differentiation of ESCs. Additionally, we demonstrated that the activity of HDAC1 and 3 is indeed required for the regulation of mesoderm gene expression. Furthermore, HDAC1 and 3 were found to interact physically with the T-box transcription factor T/Bry, which is critical for mesodermal lineage commitment. These findings indicate a key mechanism for the specific role of HDAC1 and 3 in mammalian mesoderm specification. PMID:25412078

Lv, Weiying; Guo, Xudong; Wang, Guiying; Xu, Yanxin; Kang, Jiuhong

2014-01-01

47

Snail1-dependent control of embryonic stem cell pluripotency and lineage commitment  

PubMed Central

Embryonic stem cells (ESCs) exhibit the dual properties of self-renewal and pluripotency as well as the ability to undergo differentiation that gives rise to all three germ layers. Wnt family members can both promote ESC maintenance and trigger differentiation while also controlling the expression of Snail1, a zinc-finger transcriptional repressor. Snail1 has been linked to events ranging from cell cycle regulation and cell survival to epithelial–mesenchymal transition (EMT) and gastrulation, but its role in self-renewal, pluripotency or lineage commitment in ESCs remains undefined. Here we demonstrate using isogenic pairs of conditional knockout mouse ESCs, that Snail1 exerts Wnt- and EMT independent control over the stem cell transcriptome without affecting self-renewal or pluripotency-associated functions. By contrast, during ESC differentiation, an endogenous Wnt-mediated burst in Snail1 expression regulates neuroectodermal fate while playing a required role in epiblast stem cell exit and the consequent lineage fate decisions that define mesoderm commitment. PMID:24401905

Lin, Yongshun; Li, Xiao-Yan; Willis, Amanda L.; Liu, Chengyu; Chen, Guokai; Weiss, Stephen J.

2014-01-01

48

Dicer is required for neural stem cell multipotency and lineage progression during cerebral cortex development  

PubMed Central

Background During cerebral cortex development, multipotent neural progenitor cells generate a variety of neuronal subtypes in a fixed temporal order. How a single neural progenitor cell generates the diversity of cortical projection neurons in a temporal sequence is not well understood. Based on their function in developmental timing in other systems, Dicer and microRNAs are potential candidate regulators of cellular pathways that control lineage progression in neural systems. Results Cortex-specific deletion of Dicer results in a marked reduction in the cellular complexity of the cortex, due to a pronounced narrowing in the range of neuronal types generated by Dicer-null cortical stem and progenitor cells. Instead of generating different classes of lamina-specific neurons in order over the 6-day period of neurogenesis, Dicer null cortical stem and progenitor cells continually produce one class of deep layer projection neuron. However, gliogenesis in the Dicer-null cerebral cortex was not delayed, despite the loss of multipotency and the failure of neuronal lineage progression. Conclusions We conclude that Dicer is required for regulating cortical stem cell multipotency with respect to neuronal diversity, without affecting the larger scale switch from neurogenesis to gliogenesis. The differences in phenotypes reported from different timings of Dicer deletion indicate that the molecular pathways regulating developmental transitions are notably dosage sensitive. PMID:23895693

2013-01-01

49

Dinosaur Day!  

NSDL National Science Digital Library

On Dinosaur Day, first-grade students rotated through four dinosaur-related learning stations that integrated science content with art, language arts, math, and history in a fun and time-efficient manner. The event drew parents, teachers, and students together as they helped each other discuss, write, draw, measure, mix, and record at each learning station.

Baptiste, H. P.; Nakamura, Sandra

2006-01-01

50

Digging Dinosaurs  

NSDL National Science Digital Library

Recent NSF funded expeditions to Antarctica have uncovered new dinosaur finds. This article is a report on the expeditions and on the research tools used to analyze the finds. Theories of the extinction of dinosaurs are reviewed. The site includes links to video Q&A with the paleontologists.

51

Dinosaur Tracking.  

ERIC Educational Resources Information Center

Describes paleontological studies of trace fossils (the impressions that record the animal's activity) such as dinosaur footprints. Discusses the importance of findings to our knowledge of dinosaur social behavior and community structure. Also tracts evolution of behavior from the Upper Triassic through the Upper Cretaceous, building evidence of…

Lockley, Martin

1984-01-01

52

Directing Human Induced Pluripotent Stem Cells into a Neurosensory Lineage for Auditory Neuron Replacement  

PubMed Central

Abstract Emerging therapies for sensorineural hearing loss include replacing damaged auditory neurons (ANs) using stem cells. Ultimately, it is important that these replacement cells can be patient-matched to avoid immunorejection. As human induced pluripotent stem cells (hiPSCs) can be obtained directly from the patient, they offer an opportunity to generate patient-matched neurons for transplantation. Here, we used an established neural induction protocol to differentiate two hiPSC lines (iPS1 and iPS2) and one human embryonic stem cell line (hESC; H9) toward a neurosensory lineage in vitro. Immunocytochemistry and qRT-PCR were used to analyze the expression of key markers involved in AN development at defined time points of differentiation. The hiPSC- and hESC-derived neurosensory progenitors expressed the dorsal hindbrain marker (PAX7), otic placodal marker (PAX2), proneurosensory marker (SOX2), ganglion neuronal markers (NEUROD1, BRN3A, ISLET1, ßIII-tubulin, Neurofilament kDa 160), and sensory AN markers (GATA3 and VGLUT1) over the time course examined. The hiPSC- and hESC-derived neurosensory progenitors had the highest expression levels of the sensory neural markers at 35 days in vitro. Furthermore, the neurons generated from this assay were found to be electrically active. While all cell lines analyzed produced functional neurosensory-like progenitors, variabilities in the levels of marker expression were observed between hiPSC lines and within samples of the same cell line, when compared with the hESC controls. Overall, these findings indicate that this neural assay was capable of differentiating hiPSCs toward a neurosensory lineage but emphasize the need for improving the consistency in the differentiation of hiPSCs into the required lineages. PMID:25126480

Gunewardene, Niliksha; Bergen, Nicole Van; Crombie, Duncan; Needham, Karina; Dottori, Mirella

2014-01-01

53

Directing human induced pluripotent stem cells into a neurosensory lineage for auditory neuron replacement.  

PubMed

Emerging therapies for sensorineural hearing loss include replacing damaged auditory neurons (ANs) using stem cells. Ultimately, it is important that these replacement cells can be patient-matched to avoid immunorejection. As human induced pluripotent stem cells (hiPSCs) can be obtained directly from the patient, they offer an opportunity to generate patient-matched neurons for transplantation. Here, we used an established neural induction protocol to differentiate two hiPSC lines (iPS1 and iPS2) and one human embryonic stem cell line (hESC; H9) toward a neurosensory lineage in vitro. Immunocytochemistry and qRT-PCR were used to analyze the expression of key markers involved in AN development at defined time points of differentiation. The hiPSC- and hESC-derived neurosensory progenitors expressed the dorsal hindbrain marker (PAX7), otic placodal marker (PAX2), proneurosensory marker (SOX2), ganglion neuronal markers (NEUROD1, BRN3A, ISLET1, ßIII-tubulin, Neurofilament kDa 160), and sensory AN markers (GATA3 and VGLUT1) over the time course examined. The hiPSC- and hESC-derived neurosensory progenitors had the highest expression levels of the sensory neural markers at 35 days in vitro. Furthermore, the neurons generated from this assay were found to be electrically active. While all cell lines analyzed produced functional neurosensory-like progenitors, variabilities in the levels of marker expression were observed between hiPSC lines and within samples of the same cell line, when compared with the hESC controls. Overall, these findings indicate that this neural assay was capable of differentiating hiPSCs toward a neurosensory lineage but emphasize the need for improving the consistency in the differentiation of hiPSCs into the required lineages. PMID:25126480

Gunewardene, Niliksha; Bergen, Nicole Van; Crombie, Duncan; Needham, Karina; Dottori, Mirella; Nayagam, Bryony A

2014-08-01

54

Chinese Dinosaurs  

NSDL National Science Digital Library

What's "Jurassic Park" in Mandarin? That isn't easy to say, but if you're interested in Chinese dinosaurs, then you will love the new online (and real) exhibit hosted by the Australian Museum in Sydney. A vast land containing many of the world's best-preserved dinosaur specimens, China offers remnants of many species not commonly available in Western exhibits. With lots to explore, the site features a readily accessible list of dinosaurs, each arranged under its Chinese-derived species name. Not like anything most of us have ever heard, many of the specimens look and seem familiar, at least as members of the dinosaur family. While generally well-executed, particularly worthy of note is the site's presentation of China's celebrated feathered dinosaurs, Caudipteryx zoui and Protarchaeopteryx, two curious figures believed to represent part of the great reptilian leap from land to air.

2002-01-01

55

Cytokine-Regulated GADD45G Induces Differentiation and Lineage Selection in Hematopoietic Stem Cells  

PubMed Central

Summary The balance of self-renewal and differentiation in long-term repopulating hematopoietic stem cells (LT-HSC) must be strictly controlled to maintain blood homeostasis and to prevent leukemogenesis. Hematopoietic cytokines can induce differentiation in LT-HSCs; however, the molecular mechanism orchestrating this delicate balance requires further elucidation. We identified the tumor suppressor GADD45G as an instructor of LT-HSC differentiation under the control of differentiation-promoting cytokine receptor signaling. GADD45G immediately induces and accelerates differentiation in LT-HSCs and overrides the self-renewal program by specifically activating MAP3K4-mediated MAPK p38. Conversely, the absence of GADD45G enhances the self-renewal potential of LT-HSCs. Videomicroscopy-based tracking of single LT-HSCs revealed that, once GADD45G is expressed, the development of LT-HSCs into lineage-committed progeny occurred within 36 hr and uncovered a selective lineage choice with a severe reduction in megakaryocytic-erythroid cells. Here, we report an unrecognized role of GADD45G as a central molecular linker of extrinsic cytokine differentiation and lineage choice control in hematopoiesis. PMID:25068120

Thalheimer, Frederic B.; Wingert, Susanne; De Giacomo, Pangrazio; Haetscher, Nadine; Rehage, Maike; Brill, Boris; Theis, Fabian J.; Hennighausen, Lothar; Schroeder, Timm; Rieger, Michael A.

2014-01-01

56

Stepwise renal lineage differentiation of mouse embryonic stem cells tracing in vivo development  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer We induced renal lineages from mESCs by following the in vivo developmental cues. Black-Right-Pointing-Pointer We induced nephrogenic intermediate mesoderm by stepwise addition of factors. Black-Right-Pointing-Pointer We induced two types of renal progenitor cells by reciprocal conditioned media. Black-Right-Pointing-Pointer We propose the potential role of CD24 for the enrichment of renal lineage cells. -- Abstract: The in vitro derivation of renal lineage progenitor cells is essential for renal cell therapy and regeneration. Despite extensive studies in the past, a protocol for renal lineage induction from embryonic stem cells remains unestablished. In this study, we aimed to induce renal lineages from mouse embryonic stem cells (mESC) by following in vivo developmental stages, i.e., the induction of mesoderm (Stage I), intermediate mesoderm (Stage II) and renal lineages (Stage III). For stage I induction, in accordance with known signaling pathways involved in mesoderm development in vivo, i.e., Nodal, bone morphogenic proteins (BMPs) and Wnt, we found that the sequential addition of three factors, i.e., Activin-A (A), a surrogate for Nodal signaling, during days 0-2, A plus BMP-4 (4) during days 2-4, and A4 plus lithium (L), a surrogate for Wnt signaling, during days 4-6, was most effective to induce the mesodermal marker, Brachyury. For stage II induction, the addition of retinoic acid (R) in the continuous presence of A4L during days 6-8 was most effective to induce nephrogenic intermediate mesodermal markers, such as Pax2 and Lim1. Under this condition, more than 30% of cells were stained positive for Pax2, and there was a concomitant decrease in the expression of non-mesodermal markers. For stage III induction, in resemblance to the reciprocal induction between ureteric bud (UB) and metanephric mesenchyme (MM) during kidney development, we found that the exposure to conditioned media derived from UB and MM cells was effective in inducing MM and UB markers, respectively. We also observed the emergence and gradual increase of cell populations expressing progenitor cell marker CD24 from Stage I to Stage III. These CD24{sup +} cells correlated with higher levels of expression of Brachyury at stage I, Pax2 and Lim1 at stage II and MM markers, such as WT1 and Cadherin 11, after exposure to UB-conditioned media at stage III. In conclusion, our results show that stepwise induction by tracing in vivo developmental stages was effective to generate renal lineage progenitor cells from mESC, and CD24 may serve as a useful surface marker for renal lineage cells at stage II and MM cells at stage III.

Nishikawa, Masaki, E-mail: masakiwestriver@gmail.com [Medical and Research Services, Greater Los Angeles Veterans Affairs Healthcare System at Sepulveda, North Hills, CA (United States) [Medical and Research Services, Greater Los Angeles Veterans Affairs Healthcare System at Sepulveda, North Hills, CA (United States); University of California at Los Angeles, David Geffen School of Medicine, Los Angeles, CA 91343 (United States); Yanagawa, Naomi [Medical and Research Services, Greater Los Angeles Veterans Affairs Healthcare System at Sepulveda, North Hills, CA (United States) [Medical and Research Services, Greater Los Angeles Veterans Affairs Healthcare System at Sepulveda, North Hills, CA (United States); University of California at Los Angeles, David Geffen School of Medicine, Los Angeles, CA 91343 (United States); Kojima, Nobuhiko [Institute of Industrial Science (IIS), University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)] [Institute of Industrial Science (IIS), University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Yuri, Shunsuke; Hauser, Peter V.; Jo, Oak D.; Yanagawa, Norimoto [Medical and Research Services, Greater Los Angeles Veterans Affairs Healthcare System at Sepulveda, North Hills, CA (United States) [Medical and Research Services, Greater Los Angeles Veterans Affairs Healthcare System at Sepulveda, North Hills, CA (United States); University of California at Los Angeles, David Geffen School of Medicine, Los Angeles, CA 91343 (United States)

2012-01-13

57

Dinosaur Journey  

NSDL National Science Digital Library

The Museum of Western Colorado's Dinosaur Journey Museum in Fruita, Colorado is located in the heart of dinosaur country. The Museum features exhibits and information about dinosaurs of western Colorado, eastern Utah and surrounding areas. There are robotic displays of Dilophosaurus, Stegosaurus, Apatosaurus, Triceratops, Utahraptor and T-Rex. Additionally, there are exhibits including real bones plus cast skeletons of Camarasaurus, Camptosaurus, Stegosaurus, Allosaurus, Velociraptor, Othnielia and the rare Mymoorapelta. There is a monthly newsletter available online with information on interpretive hikes and tours, an Extinct Animal of the Month, and the latest information on paleontological finds in the area.

2011-06-14

58

Dinosaur Journey  

NSDL National Science Digital Library

The Museum of Western Colorado's Dinosaur Journey Museum in Fruita, Colorado is located in the heart of dinosaur country. The Museum features exhibits and information about dinosaurs of western Colorado, eastern Utah and surrounding areas. There are robotic displays of Dilophosaurus, Stegosaurus, Apatosaurus, Triceratops, Utahraptor, T-Rex, and exhibits include real bones plus cast skeletons of Camarasaurus, Camptosaurus, Stegosaurus, Allosaurus, Velociraptor, Othnielia and the rare Mymoorapelta. There is a monthly newsletter available online with information on interpretive hikes and tours, an Extinct Animal of the Month, and the latest information on paleontological finds in the area.

59

M-CSF instructs myeloid lineage fate in single haematopoietic stem cells  

PubMed Central

Under stress conditions such as infection or inflammation the body rapidly needs to generate new blood cells that are adapted to the challenge. Haematopoietic cytokines are known to increase output of specific mature cells by affecting survival, expansion and differentiation of lineage-committed progenitors1,2, but it has been debated whether long-term haematopoietic stem cells (HSCs) are susceptible to direct lineage-specifying effects of cytokines. Although genetic changes in transcription factor balance can sensitize HSCs to cytokine instruction3, the initiation of HSC commitment is generally thought to be triggered by stochastic fluctuation in cell-intrinsic regulators such as lineage-specific transcription factors4–7, leaving cytokines to ensure survival and proliferation of the progeny cells8,9. Here we show that macrophage colony-stimulating factor (M-CSF, also called CSF1), a myeloid cytokine released during infection and inflammation, can directly induce the myeloid master regulator PU.1 and instruct myeloid cell-fate change in mouse HSCs, independently of selective survival or proliferation. Video imaging and single-cell gene expression analysis revealed that stimulation of highly purified HSCs with M-CSF in culture resulted in activation of the PU.1 promoter and an increased number of PU.1+ cells with myeloid gene signature and differentiation potential. In vivo, high systemic levels of M-CSF directly stimulated M-CSF-receptor-dependent activation of endogenous PU.1 protein in single HSCs and induced a PU.1-dependent myeloid differentiation preference. Our data demonstrate that lineage-specific cytokines can act directly on HSCs in vitro and in vivo to instruct a change of cell identity. This fundamentally changes the current view of how HSCs respond to environmental challenge and implicates stress-induced cytokines as direct instructors of HSC fate. PMID:23575636

Mossadegh-Keller, Noushine; Sarrazin, Sandrine; Kandalla, Prashanth K.; Espinosa, Leon; Stanley, E. Richard; Nutt, Stephen L.; Moore, Jordan; Sieweke, Michael H.

2013-01-01

60

Rostral-caudal distribution of Emx1-lineage stem/transit amplifying cells and lineage progression in embryonic cortex depend on hedgehog signaling.  

PubMed

Lineage progression of neural precursors to an EGF-responsive state can be promoted by several extrinsic signals, including fibroblast growth factor 2 (FGF2) and Hedgehog (Hh). It has been suggested that EGF-responsive precursors in the embryonic cerebral cortex originate in the ventral telencephalon in an FGF-dependent manner and migrate dorsally. To determine whether cortical EGF-responsive cells originate locally from dorsal precursors, we marked these precursors using Emx1-cre and the cre reporter Z/EG and observed a local origin for EGF-responsive cells. We also found a rostral-caudal difference in the abundance of self-renewing, neurogenic Emx1-lineage precursors, with more present rostrally. Deleting the Hh receptor smoothened in Emx-1 lineage cells impaired their progression to an EGF-responsive state. Moreover, loss of smoothened increased the proportion of neurogenic, self-renewing Emx1-lineage cells in caudal regions of cortex, eliminating their asymmetric distribution. Our results support the idea that Hh signaling promotes lineage progression of stem/transit amplifying cells, particularly in caudal regions of the embryonic cortex, leading to rostral-caudal differences in the abundance of neurogenic, self-renewing precursors.© 2014 Wiley Periodicals, Inc. Develop Neurobiol 74: 1096-1109, 2014. PMID:24771701

Lillien, Laura

2014-11-01

61

Small SSEA-4-positive cells from human ovarian cell cultures: related to embryonic stem cells and germinal lineage?  

PubMed Central

Background It has already been found that very small embyronic-like stem cells (VSELs) are present in adult human tissues and organs. The aim of this study was to find if there exists any similar population of cells in cell cultures of reproductive tissues and embryonic stem cells, and if these cells have any relation to pluripotency and germinal lineage. Methods and results Here we report that a population of small SSEA-4-positive cells with diameters of up to 4 ?m was isolated by fluorescence-activated cell sorting (FACS) from the human ovarian cell cultures after enzymatic degradation of adult cortex tissues. These small cells – putative ovarian stem cells – were also observed during cell culturing of up to 6 months and more. In general, small putative ovarian stem cells, isolated by FACS, showed a relatively low gene expression profile when compared to human embryonic stem cells (hESCs) and human adult fibroblasts; this may reflect the quiescent state of these cells. In spite of that, small putative ovarian stem cells expressed several genes related to primordial germ cells (PGCs), pluripotency and germinal lineage, including VASA. The PGC-related gene PRDM1 was strongly expressed in small putative ovarian stem cells; in both hESCs and fibroblasts it was significantly down-regulated. In addition, putative ovarian stem cells expressed other PGC-related genes, such as PRDM14 and DPPA3. Most of the pluripotency and germinal lineage-related genes were up-regulated in hESCs (except VASA). When compared to fibroblasts, there were several pluripotency-related genes, which were up-regulated in small putative ovarian stem cells. Similar populations of small cells were also isolated by FACS from human testicular and hESC cultures. Conclusions Our results confirm the potential embryonic-like character of small putative stem cells isolated from human adult ovaries and their possible relation to germinal lineage. PMID:23570331

2013-01-01

62

Dinosaur Teeth  

NSDL National Science Digital Library

In this classroom activity, middle school students learn what kinds of information can be gained by studying teeth. The activity opens with background information for teachers about dinosaur teeth. Working in small groups, students examine their own teeth; hypothesize about how incisors, canine teeth, and molars are used; and test their hypotheses with carrots. The activity concludes with a student worksheet that challenges them to identify the uses of different dinosaur teeth.

63

Join the Dinosaur Age  

NSDL National Science Digital Library

In this activity, learners rotate through several learning and play stations to explore dinosaurs and paleontologists. At these stations, learners use sand and dinosaur bone replicas to create a dig site and make observations, read several dinosaur books and complete dinosaur puzzles, role play as dinosaur hunters as they explore online dinosaur sites, create a dinosaur romp, listen to dinosaur music, and use clay or play dough to make dinosaurs and dinosaur tracks. This activity is featured on page 9 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

64

New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil.  

PubMed

Post-Triassic theropod, sauropodomorph, and ornithischian dinosaurs are readily recognized based on the set of traits that typically characterize each of these groups. On the contrary, most of the early members of those lineages lack such specializations, but share a range of generalized traits also seen in more basal dinosauromorphs. Here, we report on a new Late Triassic dinosaur from the Santa Maria Formation of Rio Grande do Sul, southern Brazil. The specimen comprises the disarticulated partial skeleton of a single individual, including most of the skull bones. Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits. This is not an exception among basal dinosaurs, the early radiation of which is characterized by a mosaic pattern of character acquisition, resulting in the uncertain phylogenetic placement of various early members of the group. PMID:22083251

Cabreira, Sergio F; Schultz, Cesar L; Bittencourt, Jonathas S; Soares, Marina B; Fortier, Daniel C; Silva, Lúcio R; Langer, Max C

2011-12-01

65

New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil  

NASA Astrophysics Data System (ADS)

Post-Triassic theropod, sauropodomorph, and ornithischian dinosaurs are readily recognized based on the set of traits that typically characterize each of these groups. On the contrary, most of the early members of those lineages lack such specializations, but share a range of generalized traits also seen in more basal dinosauromorphs. Here, we report on a new Late Triassic dinosaur from the Santa Maria Formation of Rio Grande do Sul, southern Brazil. The specimen comprises the disarticulated partial skeleton of a single individual, including most of the skull bones. Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits. This is not an exception among basal dinosaurs, the early radiation of which is characterized by a mosaic pattern of character acquisition, resulting in the uncertain phylogenetic placement of various early members of the group.

Cabreira, Sergio F.; Schultz, Cesar L.; Bittencourt, Jonathas S.; Soares, Marina B.; Fortier, Daniel C.; Silva, Lúcio R.; Langer, Max C.

2011-12-01

66

The origin and early radiation of dinosaurs  

NASA Astrophysics Data System (ADS)

Dinosaurs were remarkably successful during the Mesozoic and one subgroup, birds, remain an important component of modern ecosystems. Although the extinction of non-avian dinosaurs at the end of the Cretaceous has been the subject of intense debate, comparatively little attention has been given to the origin and early evolution of dinosaurs during the Late Triassic and Early Jurassic, one of the most important evolutionary radiations in earth history. Our understanding of this keystone event has dramatically changed over the past 25 years, thanks to an influx of new fossil discoveries, reinterpretations of long-ignored specimens, and quantitative macroevolutionary analyses that synthesize anatomical and geological data. Here we provide an overview of the first 50 million years of dinosaur history, with a focus on the large-scale patterns that characterize the ascent of dinosaurs from a small, almost marginal group of reptiles in the Late Triassic to the preeminent terrestrial vertebrates of the Jurassic and Cretaceous. We provide both a biological and geological background for early dinosaur history. Dinosaurs are deeply nested among the archosaurian reptiles, diagnosed by only a small number of characters, and are subdivided into a number of major lineages. The first unequivocal dinosaurs are known from the late Carnian of South America, but the presence of their sister group in the Middle Triassic implies that dinosaurs possibly originated much earlier. The three major dinosaur lineages, theropods, sauropodomorphs, and ornithischians, are all known from the Triassic, when continents were joined into the supercontinent Pangaea and global climates were hot and arid. Although many researchers have long suggested that dinosaurs outcompeted other reptile groups during the Triassic, we argue that the ascent of dinosaurs was more of a matter of contingency and opportunism. Dinosaurs were overshadowed in most Late Triassic ecosystems by crocodile-line archosaurs and showed no signs of outcompeting their rivals. Instead, the rise of dinosaurs was a two-stage process, as dinosaurs expanded in taxonomic diversity, morphological disparity, and absolute faunal abundance only after the extinction of most crocodile-line reptiles and other groups.

Brusatte, Stephen L.; Nesbitt, Sterling J.; Irmis, Randall B.; Butler, Richard J.; Benton, Michael J.; Norell, Mark A.

2010-07-01

67

Dynamic loading of electrospun yarns guides mesenchymal stem cells towards a tendon lineage  

PubMed Central

Alternative strategies are required when autograft tissue is not sufficient or available to reconstruct damaged tendons. Electrospun fibre yarns could provide such an alternative. This study investigates the seeding of human mesenchymal stem cells (hMSC) on electrospun yarns and their response when subjected to dynamic tensile loading. Cell seeded yarns sustained 3600 cycles per day for 21 days. Loaded yarns demonstrated a thickened cell layer around the scaffold?s exterior compared to statically cultured yarns, which would suggest an increased rate of cell proliferation and/or matrix deposition, whilst maintaining a predominant uniaxial cell orientation. Tensile properties of cell-seeded yarns increased with time compared to acellular yarns. Loaded scaffolds demonstrated an up-regulation in several key tendon genes, including collagen Type I. This study demonstrates the support of hMSCs on electrospun yarns and their differentiation towards a tendon lineage when mechanically stimulated. PMID:25129861

Bosworth, L.A.; Rathbone, S.R.; Bradley, R.S.; Cartmell, S.H.

2014-01-01

68

Oligodendrogliogenic and neurogenic adult subependymal zone neural stem cells constitute distinct lineages and exhibit differential responsiveness to Wnt signalling.  

PubMed

The adult mouse subependymal zone (SEZ) harbours adult neural stem cells (aNSCs) that give rise to neuronal and oligodendroglial progeny. However it is not known whether the same aNSC can give rise to neuronal and oligodendroglial progeny or whether these distinct progenies constitute entirely separate lineages. Continuous live imaging and single-cell tracking of aNSCs and their progeny isolated from the mouse SEZ revealed that aNSCs exclusively generate oligodendroglia or neurons, but never both within a single lineage. Moreover, activation of canonical Wnt signalling selectively stimulated proliferation within the oligodendrogliogenic lineage, resulting in a massive increase in oligodendrogliogenesis without changing lineage choice or proliferation within neurogenic clones. In vivo activation or inhibition of canonical Wnt signalling respectively increased or decreased the number of Olig2 and PDGFR- ? positive cells, suggesting that this pathway contributes to the fine tuning of oligodendrogliogenesis in the adult SEZ. PMID:23644466

Ortega, Felipe; Gascón, Sergio; Masserdotti, Giacomo; Deshpande, Aditi; Simon, Christiane; Fischer, Judith; Dimou, Leda; Chichung Lie, D; Schroeder, Timm; Berninger, Benedikt

2013-06-01

69

Differentiation of Human Adipose-derived Stem Cells along the Keratocyte Lineage In vitro  

PubMed Central

Purpose To evaluate differentiation of human adipose-derived stem cells (hASCs) to the keratocyte lineage by co-culture with primary keratocytes in vitro. Materials and Methods A co-culture system using transwell inserts to grow hASCs on bottom and keratocytes on top in keratocyte differentiating medium (KDM) was developed. hASCs that were cultured in complete culture medium (CCM) and KDM were used as control. After 16 days, hASCs were examined for morphologic changes and proliferation by cell count. qRT-PCR and flow cytometry were used to detect the expression of aldehyde dehydrogenase 3 family, member A1 (ALDH3A1) and keratocan. Results hASCs became more dendritic and elongated in co-culture system relative to CCM and KDM. The doubling time of the cells was longer as differentiation progressed. qRT-PCR showed a definite trend towards increased expression of both ALDH3A1 and keratocan in co-culture system despite statistically non-significant p-values. Flow cytometry showed significantly increased protein levels of ALDH3A1 and keratocan in co-culture system relative to CCM group (p < 0.001) and even relative to KDM group (p < 0.001 for ALDH3A1 and p < 0.01 for keratocan). Conclusion The co-culture method is a promising approach to induce differentiation of stem cell populations prior to in vivo applications. This study reveals an important potential for bioengineering of corneal tissue using autologous multi-potential stem cells. PMID:23936748

Zhang, Shijia; Espandar, Ladan; Imhof, Kathleen M.P.; Bunnell, Bruce A.

2013-01-01

70

Automated tracking of stem cell lineages of Arabidopsis shoot apex using local graph matching.  

PubMed

Shoot apical meristems (SAMs) of higher plants harbor stem-cell niches. The cells of the stem-cell niche are organized into spatial domains of distinct function and cell behaviors. A coordinated interplay between cell growth dynamics and changes in gene expression is critical to ensure stem-cell homeostasis and organ differentiation. Exploring the causal relationships between cell growth patterns and gene expression dynamics requires quantitative methods to analyze cell behaviors from time-lapse imagery. Although technical breakthroughs in live-imaging methods have revealed spatio-temporal dynamics of SAM-cell growth patterns, robust computational methods for cell segmentation and automated tracking of cells have not been developed. Here we present a local graph matching-based method for automated-tracking of cells and cell divisions of SAMs of Arabidopsis thaliana. The cells of the SAM are tightly clustered in space which poses a unique challenge in computing spatio-temporal correspondences of cells. The local graph-matching principle efficiently exploits the geometric structure and topology of the relative positions of cells in obtaining spatio-temporal correspondences. The tracker integrates information across multiple slices in which a cell may be properly imaged, thus providing robustness to cell tracking in noisy live-imaging datasets. By relying on the local geometry and topology, the method is able to track cells in areas of high curvature such as regions of primordial outgrowth. The cell tracker not only computes the correspondences of cells across spatio-temporal scale, but it also detects cell division events, and identifies daughter cells upon divisions, thus allowing automated estimation of cell lineages from images captured over a period of 72 h. The method presented here should enable quantitative analysis of cell growth patterns and thus facilitating the development of in silico models for SAM growth. PMID:20042023

Liu, Min; Yadav, Ram Kishor; Roy-Chowdhury, Amit; Reddy, G Venugopala

2010-04-01

71

Mechanical Modulation of Nascent Stem Cell Lineage Commitment in Tissue Engineering Scaffolds  

PubMed Central

Taking inspiration from tissue morphogenesis in utero, this study tests the concept of using tissue engineering scaffolds as delivery devices to modulate emergent structure-function relationships at early stages of tissue genesis. We report on the use of a combined computational fluid dynamics (CFD) modeling, advanced manufacturing methods, and experimental fluid mechanics (micro-piv and strain mapping) for the prospective design of tissue engineering scaffold geometries that deliver spatially resolved mechanical cues to cells seeded within. When subjected to a constant magnitude global flow regime, the local scaffold geometry dictates the magnitudes of mechanical stresses and strains experienced by a given cell, and in a spatially resolved fashion, similar to patterning during morphogenesis. In addition, early markers of mesenchymal stem cell lineage commitment relate significantly to the local mechanical environment of the cell. Finally, by plotting the range of stress-strain states for all data corresponding to nascent cell lineage commitment (95% CI), we begin to “map the mechanome”, defining stress-strain states most conducive to targeted cell fates. In sum, we provide a library of reference mechanical cues that can be delivered to cells seeded on tissue engineering scaffolds to guide target tissue phenotypes in a temporally and spatially resolved manner. Knowledge of these effects allows for prospective scaffold design optimization using virtual models prior to prototyping and clinical implementation. Finally, this approach enables the development of next generation scaffolds cum delivery devices for genesis of complex tissues with heterogenous properties, e.g., organs, joints or interface tissues such as growth plates. PMID:23660249

Song, Min Jae; Dean, David; Tate, Melissa L. Knothe

2013-01-01

72

Suppression of the Stem Cell Antigen-1 Response and Granulocyte Lineage Expansion by Alcohol during Septicemia  

PubMed Central

Objective Granulocytopenia frequently occurs in alcohol abusers suffering from severe bacterial infection, which strongly correlates with poor clinical outcome. Knowledge of the molecular mechanisms underlying the granulopoietic response to bacterial infection remains limited. This study investigated the involvement of Stem Cell Antigen-1 (Sca-1) expression by granulocyte lineage-committed progenitors in the granulopoietic response to septicemia and how alcohol affected this response. Design Laboratory investigation. Setting University laboratory. Subjects Male Balb/c mice. Interventions Thirty minutes after intraperitoneal injection of alcohol (20% ethanol in saline at 5g of ethanol/Kg) or saline, mice received intravenous Escherichia coli (E.coli) challenge. Measurements and Main Results E. coli septicemia activated Sca-1 expression by marrow immature granulocyte differentiation antigen-1 (Gr1)lo precursors which correlated with an increase in proliferation, CFU-GM production, and expansion of this granulopoietic precursor cell pool. Acute alcohol treatment suppressed Sca-1 activation and inhibited the infection-induced increases in proliferation, CFU-GM production, and expansion the of Gr1lo cell population. Consequently, recovery of the marrow mature Gr1hi cell population following E.coli challenge was impaired. Sca-1 was induced in sorted Gr1+Sca1- cells by LPS-stimulated JNK activation that was also inhibited by alcohol. Furthermore, Sca-1 knockout (KO) mice failed to expand the marrow Gr1lo cell pool and demonstrated fewer newly produced granulocytes in the circulation following E.coli challenge. Conclusions Alcohol suppresses the Sca-1 response in granulocyte lineage-committed precursors and restricts granulocyte production during septicemia, which may serve as a novel mechanism underlying impaired host defense in alcohol abusers. PMID:21602669

Melvan, John N.; Siggins, Robert W.; Bagby, Gregory J.; Stanford, William L.; Welsh, David; Nelson, Steve; Zhang, Ping

2011-01-01

73

Dinosaur Timeline  

NSDL National Science Digital Library

In this classroom activity, young students gain an understanding of geologic time. The activity opens with background information for teachers about carbon and radiometric datings. After discussing important events in their lives, students create an impromptu timeline. Working as a class, students place predetermined events from Earth's past on a lengthy timeline and identify the window of time during which the dinosaurs lived.

74

Dinosaur Roundup.  

ERIC Educational Resources Information Center

The use of programs on the topic of dinosaurs in interdisciplinary exercises which may include mathematics, science, history, and language arts is described. Reviews of 16 different computer programs are included. Possible misconceptions and how they are dealt with in various programs are discussed. (CW)

Eiser, Leslie

1990-01-01

75

Dinosaur Illustrations  

NSDL National Science Digital Library

These twelve dark-line dinosaur drawings can be used as either a research or coloring activity. Overhead transparencies of the drawings can be projected to make large traced images of the animals. The site includes drawings of Ankylosaurus, Barosaurus, Coelophysis, Diplodocus, Iguanodon, Ornithomimus, Pachycephalosaurus, Parasaurolophus, Plateosaurus, Stegosaurus, Triceratops, and Tyrannosaurus rex.

76

Grouping Dinosaurs  

NSDL National Science Digital Library

In this classroom activity, young students are introduced to sets and subsets. The activity opens with background information for teachers about cladistics. After brainstorming different ways to group the class itself, students work in small groups to identify subsets of coins. The groups then complete a worksheet that challenges them to group dinosaurs into sets and subsets and share their results with the class.

77

Dinosaur Dig  

NSDL National Science Digital Library

This is an activity about dinosaurs, fossils, and the work of paleontologists. Learners use hand tools (paint brushes, scoops, and sifters) to unearth fossil specimens in tubs of birdseed. This resource includes definitions of fossils and paleontologists as well as discussion questions to further learning.

Omsi

2004-01-01

78

Dinosaur Floor  

NSDL National Science Digital Library

This Classroom of the Future (COTF) resource explores dinosaurs and the possible causes of their extinction, including orbital changes in the Earth, volcanoes, disease, a supernova, and asteroid impact. The site provides a brief, illustrated essay for each theory, as well as links to related sites.

79

Dinosaur Flesh and Bones  

NSDL National Science Digital Library

In this activity, learners explore dinosaur skeletons. First, learners listen to "Bones, Bones, Dinosaur Bones" by Byron Barton to learn about the difference between pictures of dinosaurs that have skin and muscle (fleshed-out) and those that show skeletons. Then, learners match pictures of dinosaurs to pictures of the dinosaurs' skeletons. Learners can also explore other animal bones and skeletons online and/or reassemble paper dinosaur skeletons. This activity can also be used to help learners explore scale as they realize that large dinosaurs had large skeletons and small dinosaurs had small skeletons. This activity is featured on page 37 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

80

Dinosaur evolution. A Jurassic ornithischian dinosaur from Siberia with both feathers and scales.  

PubMed

Middle Jurassic to Early Cretaceous deposits from northeastern China have yielded varied theropod dinosaurs bearing feathers. Filamentous integumentary structures have also been described in ornithischian dinosaurs, but whether these filaments can be regarded as part of the evolutionary lineage toward feathers remains controversial. Here we describe a new basal neornithischian dinosaur from the Jurassic of Siberia with small scales around the distal hindlimb, larger imbricated scales around the tail, monofilaments around the head and the thorax, and more complex featherlike structures around the humerus, the femur, and the tibia. The discovery of these branched integumentary structures outside theropods suggests that featherlike structures coexisted with scales and were potentially widespread among the entire dinosaur clade; feathers may thus have been present in the earliest dinosaurs. PMID:25061209

Godefroit, Pascal; Sinitsa, Sofia M; Dhouailly, Danielle; Bolotsky, Yuri L; Sizov, Alexander V; McNamara, Maria E; Benton, Michael J; Spagna, Paul

2014-07-25

81

The potential of dental stem cells differentiating into neurogenic cell lineage after cultivation in different modes in vitro.  

PubMed

Abstract Trauma or degenerative diseases of the central nervous system (CNS) cause the loss of neurons or glial cells. Stem cell transplantation has become a vital strategy for CNS regeneration. It is necessary to effectively induce nonneurogenic stem cells to differentiate into neurogenic cell lineages because of the limited source of neurogenic stem cells, relatively difficult cultivation, and ethical issues. Previous studies have found that dental stem cells can be used for transplantation therapy. The aim of this study was to explore a better inductive mode and time point for dental stem cells to differentiate into neural-like cells and evaluate a better candidate cell. In this study, dental follicle stem cells (DFSCs), dental papilla stem cells (DPSCs), and stem cells from apical papilla (SCAPs) were cultivated in five different modes. The proliferation ability, morphology, and expression of neural marker genes were analyzed. Results showed that DFSCs showed a higher proliferation potential. The proliferation was decreased after cultivation in chemical inductive medium as cultivation modes 3 and 5. The cells could present neural-like cell morphology after cultivation with human epidermal growth factor (EGF) and fibroblast growth factor-basic (bFGF) as cultivation modes 4 and 5. The vast majority of DFSCs gene expression levels in mode 4 on the third day was upregulated significantly. In conclusion, our data suggested that different dental stem cells exhibited different neural differentiation potentials. DFSCs might be the better candidate cell type. Furthermore, cultivation mode 4 and timing of the third day may promote differentiation into neurogenic cell lineages more effectively before transplantation to treat neurological diseases. PMID:25072651

Yang, Chao; Sun, Liang; Li, Xinghan; Xie, Li; Yu, Mei; Feng, Lian; Jiang, Zongting; Guo, Weihua; Tian, Weidong

2014-10-01

82

Differentiated Troy+ chief cells act as 'reserve' stem cells to generate all lineages of the stomach epithelium  

PubMed Central

SUMMARY Proliferation of the self-renewing epithelium of the gastric corpus occurs almost exclusively in the isthmus of the glands, from where cells migrate bi-directionally towards pit and base. The isthmus is therefore generally viewed as the stem cell zone. We find that the stem cell marker Troy is expressed at the gland base by a small subpopulation of fully differentiated chief cells. By lineage tracing using a Troy-eGFP-ires-CreERT2 allele, single marked chief cells are shown to generate entirely labeled gastric units over periods of months. This phenomenon accelerates upon tissue damage. Troy+ chief cells can be cultured to generate long-lived gastric organoids. Troy marks a specific subset of chief cells that display plasticity in that they are capable of replenishing entire gastric units, essentially serving as quiescent ‘reserve’ stem cells. These observations challenge the notion that stem cell hierarchies represent a 'one-way street'. PMID:24120136

Stange, Daniel E.; Koo, Bon-Kyoung; Huch, Meritxell; Sibbel, Greg; Basak, Onur; Lyubimova, Anna; Kujala, Pekka; Bartfeld, Sina; Koster, Jan; Geahlen, Jessica H.; Peters, Peter J.; van Es, Johan H.; van de Wetering, Marc; Mills, Jason C.; Clevers, Hans

2014-01-01

83

Tet1 and Tet2 regulate 5-hydroxymethylcytosine production and cell lineage specification in mouse embryonic stem cells  

PubMed Central

SUMMARY TET-family enzymes convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) in DNA. Here we show that Tet1 and Tet2 are Oct4-regulated enzymes that together sustain 5hmC in mouse embryonic stem (ES) cells, and are induced concomitantly with 5hmC during reprogramming of fibroblasts to induced pluripotent stem cells. ES cells depleted of Tet1 by RNAi show diminished expression of the Nodal antagonist Lefty1, and display hyperactive Nodal signalling and skewed differentiation into the endoderm-mesoderm lineage in embryoid bodies in vitro. In Fgf4- and heparin-supplemented culture conditions, Tet1-depleted ES cells activate the trophoblast stem cell lineage determinant Elf5 and can colonize the placenta in mid-gestation embryo chimeras. Consistent with these findings, Tet1-depleted ES cells form aggressive hemorrhagic teratomas with increased endoderm, reduced neuroectoderm and ectopic appearance of trophoblastic giant cells. Thus 5hmC is a novel epigenetic modification associated with the pluripotent state, and Tet1 functions to regulate the lineage differentiation potential of ES cells. PMID:21295276

Koh, Kian Peng; Yabuuchi, Akiko; Rao, Sridhar; Huang, Yun; Cunniff, Kerrianne; Nardone, Julie; Laiho, Asta; Tahiliani, Mamta; Sommer, Cesar A.; Mostoslavsky, Gustavo; Lahesmaa, Riitta; Orkin, Stuart H.; Rodig, Scott J.; Daley, George Q.; Rao, Anjana

2011-01-01

84

Dinosaur taphonomy  

NSDL National Science Digital Library

In preparation for this assignment, students have read a brief section in their textbook on the fossilization process as it relates to dinosaurs. In addition they will have had one lecture on taphonomy that briefly covers the processes that transpire from the death of a dinosaur until its discovery by a paleontologist. Students work in groups. Each group is given a quarry map of a dinosaur locality and no other information. The exercise is framed as detecive work, where the "scene of the crime" is represented by the quarry map. The objective is to gather clues to make an informed intepretation. Students can obtain additional clues, but to do so, they must formulate a hypothesis that can be tested by the information they seek. However, they only get to formulate 10 hypotheses. An untestable hypothesis wastes a potential clue. Once students have gathered all their clues, they are encouraged to discuss the significance. Students write up their own interpretation and its limitations individually. The exercise gives students practice with taphonomic data and both its potential and limitations; hypothesis formulation; and examining differing viewpoints as group discussions often lead to debates about what information would be most important.

Varricchio, David

85

What Makes a Dinosaur a Dinosaur?  

NSDL National Science Digital Library

This activity opens with background information for teachers about dinosaurs. As a class, students compare the stance of lizards and dinosaurs in drawings and try to replicate both reptiles' walks. Students learn that some paleontologists classify birds as dinosaurs, and then work in groups to compare a Tyrannosaurus rex skeleton with pictures of birds.

86

Dinosaur Books for Educators  

NSDL National Science Digital Library

This dinosaur reference list has 18 books that are recommended for learning more about Dinosaurs. The author, publisher, and publishing date are given for each title. The list includes encyclopedias of dinosaurs, real-life tales of fossil hunts, hands-on activities for students, and an examination of the link between birds and dinosaurs.

87

Influence of discrete and continuous culture conditions on human mesenchymal stem cell lineage choice in RGD concentration gradient hydrogels.  

PubMed

Stem cells have shown lineage-specific differentiation when cultured on substrates possessing signaling groups derived from the native tissue. A distinct determinant in this process is the concentration of the signaling motif. While several groups have been working actively to determine the specific factors, concentrations, and mechanisms governing the differentiation process, many have been turning to combinatorial and gradient approaches in attempts to optimize the multiple chemical and physical parameters needed for the next advance. However, there has not been a direct comparison between the cellular behavior and differentiation of human mesenchymal stem cells cultured in gradient and discrete substrates, which quantitates the effect of differences caused by cell-produced, soluble factors due to design differences between the culture systems. In this study, the differentiation of human mesenchymal stem cells in continuous and discrete polyethylene glycol dimethacrylate (PEGDM) hydrogels containing an RGD concentration gradient from 0 to 14 mM were examined to study the effects of the different culture conditions on stem-cell behavior. Culture condition was found to affect every osteogenic (alkaline phosphatase, Runx 2, type 1 collagen, bone sailoprotein, and calcium content) and adipogenic marker (oil red and peroxisome proliferator-activated receptor gamma) examined regardless of RGD concentration. Only in the continuous gradient culture did RGD concentration affect human mesenchymal stem-cell lineage commitment with low RGD concentrations expressing higher osteogenic differentiation than high RGD concentrations. Conversely, high RGD concentrations expressed higher adipogenic differentiation than low RGD concentrations. Cytoskeletal actin organization was only affected by culture condition at low RGD concentrations, indicating that it played a limited role in the differences in lineage commitment observed. Therefore, the role of discrete versus gradient strategies in high-throughput experimentation needs to be considered when designing experiments as we show that the respective strategies alter cellular outcomes even though base scaffolds have similar material and chemical properties. PMID:23844746

Smith Callahan, Laura A; Policastro, Gina M; Bernard, Sharon L; Childers, Erin P; Boettcher, Ronna; Becker, Matthew L

2013-09-01

88

Heterogeneous mixed-lineage differentiation of mouse embryonic stem cells induced by conditioned media from a549 cells.  

PubMed

Conditioned media (CM) of transformed cells, such as the human lung-derived A549 cells, is a useful tool for directing differentiation of embryonic stem cells (ESCs). Previous work indicates that A549-CM induced pulmonary differentiation of mouse ESCs (mESCs). In this study, we compared the effects of A549-CM treatment on the differentiation of mESCs organized in monolayer or embryoid bodies. We analyzed the cultures treated with A549-CM using specific lineage markers by quantitative polymerase chain reaction (qPCR) and lineage-focused PCR arrays and demonstrated heterogeneous CM-induced differentiation. We then constructed bioinformatics-based gene networks to establish correlations between the upregulated lineage-specific genes and proteins in the A549-CM identified by proteomic analysis. Network analysis supported the phenotypic and genotypic heterogeneic differentiation of mESCs into multiple cell lineages via enriched stemness, cardiovascular, neuronal, and lung development gene ontologies (GOs). The significant enrichment toward lung ontologies was specific for treatment with A549-CM, but not CM of liver (HepG2) and pancreas (Capan-1) cells. Based on network analysis, we identified laminin alpha5, prosaposin, lamin A/C, dickkopf homolog 1, clusterin, and calreticulin as the most relevant proteins related to the enrichment of lung GOs. We validated the effects of laminin isoforms on mESC differentiation in vitro and found enriched differential induction of surfactant protein gene expression. Our data suggest that A549-CM can be used for identifying secreted proteins for the heterogeneous mixed-lineage differentiation of mESCs toward a variety of lung-relevant cells. Such a heterogeneous cell population will be required for the in vitro generation of complex lung tissue and mixed cell populations for regenerative pulmonary therapy. PMID:24720740

Lecht, Shimon; Gerstenhaber, Jonathan A; Stabler, Collin T; Pimton, Pimchanok; Karamil, Seda; Marcinkiewicz, Cezary; Schulman, Edward S; Lelkes, Peter I

2014-08-15

89

X-ray Dinosaurs  

NSDL National Science Digital Library

In this activity, learners explore dinosaur fossils and skeletons. First, learners listen to "Tyrannosaurus Rex" by Daniel Cohen to learn about T. rex dinosaurs specifically. Then, learners make dinosaur tracings and drawings similar to x-rays. Learners can repeat the activity using pictures of other dinosaurs to compare and contrast various dinosaurs. This activity is featured on page 38 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

90

Make a Dinosaur Model  

NSDL National Science Digital Library

In this activity, learners explore dinosaur skeletons, anatomy, and locomotion. Learners compare and contrast dinosaur skeletons and drawings. Learners also work in groups to reassemble "pieces" to form dinosaur skeletons. Finally, learners create and pose paper dinosaur models with moveable parts and list different actions or movements the dinosaurs can do including eating, walking, and sleeping. This activity is featured on page 39 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

91

The Ornithischian Dinosaurs  

NSDL National Science Digital Library

This site introduces a group of dinosaurs called ornithischians. There were many kinds of ornithischian dinosaurs dating back to the early Jurassic. The Ornithopoda included the hadrosaurs (duck-billed dinosaurs), the iguanodontids, the heterodontosaurs, the hypsilophodontids, and various others. The Ceratopsia included the horned dinosaurs, while the Ankylosauria and Stegosauria (now usually grouped together in the Thyreophora) included various types of armored dinosaurs. The Pachycephalosauria included the extremely thick-skulled pachycephalosaurs.

92

Adult Thymus Contains FoxN1(-) Epithelial Stem Cells that Are Bipotent for Medullary and Cortical Thymic Epithelial Lineages.  

PubMed

Within the thymus, two major thymic epithelial cell (TEC) subsets-cortical and medullary TECs-provide unique structural and functional niches for T cell development and establishment of central tolerance. Both lineages are believed to originate from a common progenitor cell, yet the cellular and molecular identity of these bipotent TEC progenitors/stem cells remains ill defined. Here we identify rare stromal cells in the murine adult thymus, which under low-attachment conditions formed spheres (termed "thymospheres"). These thymosphere-forming cells (TSFCs) displayed the stemness features of being slow cycling, self-renewing, and bipotent. TSFCs could be significantly enriched based on their distinct surface antigen phenotype. The FoxN1 transcription factor was dispensable for TSFCs maintenance in situ and for commitment to the medullary and cortical TEC lineages. In summary, this study presents the characterization of the adult thymic epithelial stem cells and demonstrates the dispensability of FoxN1 function for their stemness. PMID:25148026

Ucar, Ahmet; Ucar, Olga; Klug, Paula; Matt, Sonja; Brunk, Fabian; Hofmann, Thomas G; Kyewski, Bruno

2014-08-21

93

Three RNA Binding Proteins Form a Complex to Promote Differentiation of Germline Stem Cell Lineage in Drosophila  

PubMed Central

In regenerative tissues, one of the strategies to protect stem cells from genetic aberrations, potentially caused by frequent cell division, is to transiently expand the stem cell daughters before further differentiation. However, failure to exit the transit amplification may lead to overgrowth, and the molecular mechanism governing this regulation remains vague. In a Drosophila mutagenesis screen for factors involved in the regulation of germline stem cell (GSC) lineage, we isolated a mutation in the gene CG32364, which encodes a putative RNA-binding protein (RBP) and is designated as tumorous testis (tut). In tut mutant, spermatogonia fail to differentiate and over-amplify, a phenotype similar to that in mei-P26 mutant. Mei-P26 is a TRIM-NHL tumor suppressor homolog required for the differentiation of GSC lineage. We found that Tut binds preferentially a long isoform of mei-P26 3?UTR, and is essential for the translational repression of mei-P26 reporter. Bam and Bgcn are both RBPs that have also been shown to repress mei-P26 expression. Our genetic analyses indicate that tut, bam, or bgcn is required to repress mei-P26 and to promote the differentiation of GSCs. Biochemically, we demonstrate that Tut, Bam, and Bgcn can form a physical complex in which Bam holds Tut on its N-terminus and Bgcn on its C-terminus. Our in vivo and in vitro evidence illustrate that Tut acts with Bam, Bgcn to accurately coordinate proliferation and differentiation in Drosophila germline stem cell lineage. PMID:25412508

Zhao, Shaowei; Geng, Qing; Gao, Yu; Li, Xin; Zhang, Yang; Wang, Zhaohui

2014-01-01

94

Dinosaur Breath  

NSDL National Science Digital Library

This simple demonstration is about the role of dinosaurs in the carbon cycle and the eventual storage of excess carbon in the form of chalk. Students will come to understand the importance of the carbon cycle, appreciate that it has always been essential for life on earth, and appreciate the role of the oceans as a carbon sink. The instructor guide contains detailed background material, learning goals, alignment to national standards, grade level/time, details on materials and preparation, procedure, assessment ideas, and modifications for alternative learners.

95

Dinosaur Breath  

NSDL National Science Digital Library

Through discussion and hands-on experimentation, students learn about the geological (ancient) carbon cycle. They investigate the role of dinosaurs in the carbon cycle and the eventual storage of carbon in the form of chalk. Students discover how the carbon cycle has been occurring for millions of years and is necessary for life on Earth. Finally, they may extend their knowledge to the concept of global warming and how engineers are working to understand the carbon cycle and reduce harmful CO2 emissions.

Integrated Teaching And Learning Program

96

The role of Importin-?s in the maintenance and lineage commitment of mouse embryonic stem cells?  

PubMed Central

Members of the Importin-? family recognize nuclear localization signals (NLS) and nuclear export signals (NES). These proteins play important roles in various nucleocytoplasmic transport processes in cells. Here, we examined the expression patterns of 21 identified Importin-? genes in mouse embryonic stem cells (mESCs), mouse embryonic fibroblast (MEF) and mESCs differentiated into neural ectoderm (NE) or mesoendoderm (ME). We observed striking differences in the Importin-? mRNA expression levels within these cell types. We also found that knockdown of selected Importin-? genes led to suppression of Nanog, and altered the balance of Oct4/Sox2 expression ratio, which is important for NE/ME lineage choice. Furthermore, we demonstrated that knockdown of XPO4, RanBP17, RanBP16, or IPO7 differentially affected the lineage selection of differentiating mESCs. More specifically, knockdown of XPO4 selectively stimulated the mESC differentiation towards definitive endoderm, while concomitantly inhibiting NE differentiation. RanBP17 knockdown also promoted endodermal differentiation with no effect on NE differentiation. RanBP16 knockdown caused differentiation into ME, while IPO7 knockdown inhibited NE differentiation, without obvious effects on the other lineages. Collectively, our results suggest that Importin-?s play important roles in cell fate determination processes of mESCs, such as in the maintenance of pluripotency or selection of lineage during differentiation. PMID:24490135

Sangel, Percival; Oka, Masahiro; Yoneda, Yoshihiro

2014-01-01

97

Gamma paleohexaploidy in the stem lineage of core eudicots: significance for MADS-box gene and species diversification.  

PubMed

Comparative genome biology has unveiled the polyploid origin of all angiosperms and the role of recurrent polyploidization in the amplification of gene families and the structuring of genomes. Which species share certain ancient polyploidy events, and which do not, is ill defined because of the limited number of sequenced genomes and transcriptomes and their uneven phylogenetic distribution. Previously, it has been suggested that most, but probably not all, of the eudicots have shared an ancient hexaploidy event, referred to as the gamma triplication. In this study, detailed phylogenies of subfamilies of MADS-box genes suggest that the gamma triplication has occurred before the divergence of Gunnerales but after the divergence of Buxales and Trochodendrales. Large-scale phylogenetic and K(S)-based approaches on the inflorescence transcriptomes of Gunnera manicata (Gunnerales) and Pachysandra terminalis (Buxales) provide further support for this placement, enabling us to position the gamma triplication in the stem lineage of the core eudicots. This triplication likely initiated the functional diversification of key regulators of reproductive development in the core eudicots, comprising 75% of flowering plants. Although it is possible that the gamma event triggered early core eudicot diversification, our dating estimates suggest that the event occurred early in the stem lineage, well before the rapid speciation of the earliest core eudicot lineages. The evolutionary significance of this paleopolyploidy event may thus rather lie in establishing a species lineage that was resilient to extinction, but with the genomic potential for later diversification. We consider that the traits generated from this potential characterize extant core eudicots both chemically and morphologically. PMID:22821009

Vekemans, Dries; Proost, Sebastian; Vanneste, Kevin; Coenen, Heleen; Viaene, Tom; Ruelens, Philip; Maere, Steven; Van de Peer, Yves; Geuten, Koen

2012-12-01

98

What Makes a Dinosaur a Dinosaur?  

NSDL National Science Digital Library

In this classroom activity, middle school students learn what distinguishes dinosaurs from other animals. The activity opens with background information for teachers about these prehistoric reptiles. As a class, students compare the stance of lizards and dinosaurs in pictures and try to replicate both reptiles' walks. Students then learn that Museum paleontologists classify birds as dinosaurs, and work in groups to compare a T. rex skeleton with pictures of birds.

99

Environmental signals regulate lineage choice and temporal maturation of neural stem cells from human embryonic stem cells  

Microsoft Academic Search

Human embryonic stem cells (hESCs) are a potential source of defined tissue for cell-based therapies in regenerative neurology. In order for this potential to be realized, there is a need for the evaluation of the behaviour of human embryonic stem cell-derived neural stem cells (hES-NSCs) both in the normal and the injured CNS. Using normal tissue and two experimental models,

Alexis J. Joannides; Daniel J. Webber; Olivier Raineteau; Claire Kelly; Karen-Amanda Irvine; Colin Watts; Anne E. Rosser; Paul J. Kemp; William F. Blakemore; Alastair Compston; Maeve A. Caldwell; Nicholas D. Allen; Siddharthan Chandran

2007-01-01

100

Pyrvinium, A Potent Small Molecule WNT Inhibitor, Increases Engraftment And Inhibits Lineage Commitment Of Mesenchymal Stem Cells (MSCs)  

PubMed Central

We and others have found that Wnt signaling inhibition is important in mesenchymal stem cell (MSC) self-renewal. Pyrvinium was identified as a potent Wnt inhibitor in a chemical screen for small molecules. In the present study we hypothesized that pyrvinium will enhance MSC self-renewal to improve the clinical efficacy of MSC therapy. Pyrvinium increased MSC proliferation in vitro while inhibiting their osteogenic and chondrogenic lineage commitment by reducing cytoplasmic ?-catenin. Although MSCs are a promising target for cell therapy, strategies to enhance their survival and maintain their stemness in the wounded area are essential. Using an in vivo model of granulation tissue formation, we demonstrated that pyrvinium enhanced long-term MSC engraftment. Pyrvinium treated MSC-generated granulation tissue also demonstrated less ectopic differentiation into bone or cartilage. This study highlights the potential of using a therapeutic Wnt inhibitor to enhance MSC-driven regenerative therapy. PMID:22332749

Saraswati, Sarika; Deskins, Desirae L.; Holt, Ginger E.; Young, Pampee P.

2012-01-01

101

What's New, Dinosaur?  

ERIC Educational Resources Information Center

Activities and information relating to dinosaurs are presented, including: study of warm- and cold-blooded animals; research about recent dinosaur discoveries; track-making; studying and making fossils; and extinction theories. (CB)

Prime, Carol Spirkoff; Cox, Judy

1987-01-01

102

Retinoic acid activation of the ERK pathway is required for embryonic stem cell commitment into the adipocyte lineage.  

PubMed

Mouse embryonic stem (ES) cells are pluripotent cells that differentiate into multiple cell lineages. The commitment of ES cells into the adipocyte lineage is dependent on an early 3-day treatment with all-trans retinoic acid (RA). To characterize the molecular mechanisms underlying this process, we examined the contribution of the extracellular-signal-regulated kinase (ERK) pathway. Treatment of ES cell-derived embryoid bodies with RA resulted in a prolonged activation of the ERK pathway, but not the c-Jun N-terminal kinase, p38 mitogen-activated protein kinase or phosphoinositide 3-kinase pathways. To investigate the role of ERK activation, co-treatment of RA with PD98059, a specific inhibitor of the ERK signalling pathway, prevented both adipocyte formation and expression of the adipogenic markers, adipocyte lipid-binding protein and peroxisome-proliferator-activated receptor gamma. Furthermore, we show that ERK activation is required only during RA treatment. PD98059 does not interfere with the commitment of ES cells into other lineages, such as neurogenesis, myogenesis and cardiomyogenesis. As opposed to the controversial role of the ERK pathway in terminal differentiation, our results clearly demonstrate that this pathway is specifically required at an early stage of adipogenesis, corresponding to the RA-dependent commitment of ES cells. PMID:11802792

Bost, Frédéric; Caron, Leslie; Marchetti, Irène; Dani, Christian; Le Marchand-Brustel, Yannick; Binétruy, Bernard

2002-02-01

103

Retinoic acid activation of the ERK pathway is required for embryonic stem cell commitment into the adipocyte lineage.  

PubMed Central

Mouse embryonic stem (ES) cells are pluripotent cells that differentiate into multiple cell lineages. The commitment of ES cells into the adipocyte lineage is dependent on an early 3-day treatment with all-trans retinoic acid (RA). To characterize the molecular mechanisms underlying this process, we examined the contribution of the extracellular-signal-regulated kinase (ERK) pathway. Treatment of ES cell-derived embryoid bodies with RA resulted in a prolonged activation of the ERK pathway, but not the c-Jun N-terminal kinase, p38 mitogen-activated protein kinase or phosphoinositide 3-kinase pathways. To investigate the role of ERK activation, co-treatment of RA with PD98059, a specific inhibitor of the ERK signalling pathway, prevented both adipocyte formation and expression of the adipogenic markers, adipocyte lipid-binding protein and peroxisome-proliferator-activated receptor gamma. Furthermore, we show that ERK activation is required only during RA treatment. PD98059 does not interfere with the commitment of ES cells into other lineages, such as neurogenesis, myogenesis and cardiomyogenesis. As opposed to the controversial role of the ERK pathway in terminal differentiation, our results clearly demonstrate that this pathway is specifically required at an early stage of adipogenesis, corresponding to the RA-dependent commitment of ES cells. PMID:11802792

Bost, Frederic; Caron, Leslie; Marchetti, Irene; Dani, Christian; Le Marchand-Brustel, Yannick; Binetruy, Bernard

2002-01-01

104

The Dinosaur Name Game  

NSDL National Science Digital Library

In this classroom activity, middle school students explore the Greek and Latin root words used to create dinosaur names. The activity opens with background information about how dinosaurs are named. As a class, students explore the Greek and Latin roots of some familiar terms. Working individually, students complete a worksheet that challenges them to translate the meaning of seven dinosaurs' names. Then, working in pairs, students create their own dinosaur, name it, and describe how it behaves.

105

Human Mesenchymal Stem Cells Derived From Limb Bud Can Differentiate into All Three Embryonic Germ Layers Lineages  

PubMed Central

Abstract Mesenchymal stem cells (MSCs) have been isolated from many sources, including adults and fetuses. Previous studies have demonstrated that, compared with their adult counterpart, fetal MSCs with several remarkable advantages may be a better resource for clinical applications. In this study, we successfully isolated a rapidly proliferating cell population from limb bud of aborted fetus and termed them “human limb bud–derived mesenchymal stem cells” (hLB-MSCs). Characteristics of their morphology, phenotype, cell cycle, and differentiation properties were analyzed. These adherent cell populations have a typically spindle-shaped morphology. Flow cytometry analysis showed that hLB-MSCs are positive for CD13, CD29, CD90, CD105, and CD106, but negative for CD3, CD4, CD5, CD11b, CD14, CD15, CD34, CD45, CD45RA, and HLA-DR. The detection of cell cycle from different passages indicated that hLB-MSCs have a similar potential for propagation during long culture in vitro. The most novel finding here is that, in addition to their mesodermal differentiation (osteoblasts and adipocytes), hLB-MSCs can also differentiated into extramesenchymal lineages, such as neural (ectoderm) and hepatic (endoderm) progenies. These results indicate that hLB-MSCs have a high level of plasticity and can differentiate into cell lineages from all three embryonic layers in vitro. PMID:22775353

Jiao, Fei; Wang, Juan; Dong, Zhao-lun; Wu, Min-juan; Zhao, Ting-bao; Li, Dan-dan

2012-01-01

106

Transient accumulation of 5-carboxylcytosine indicates involvement of active demethylation in lineage specification of neural stem cells.  

PubMed

5-Methylcytosine (5mC) is an epigenetic modification involved in regulation of gene activity during differentiation. Tet dioxygenases oxidize 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). Both 5fC and 5caC can be excised from DNA by thymine-DNA glycosylase (TDG) followed by regeneration of unmodified cytosine via the base excision repair pathway. Despite evidence that this mechanism is operative in embryonic stem cells, the role of TDG-dependent demethylation in differentiation and development is currently unclear. Here, we demonstrate that widespread oxidation of 5hmC to 5caC occurs in postimplantation mouse embryos. We show that 5fC and 5caC are transiently accumulated during lineage specification of neural stem cells (NSCs) in culture and in vivo. Moreover, 5caC is enriched at the cell-type-specific promoters during differentiation of NSCs, and TDG knockdown leads to increased 5fC/5caC levels in differentiating NSCs. Our data suggest that active demethylation contributes to epigenetic reprogramming determining lineage specification in embryonic brain. PMID:24882006

Wheldon, Lee M; Abakir, Abdulkadir; Ferjentsik, Zoltan; Dudnakova, Tatiana; Strohbuecker, Stephanie; Christie, Denise; Dai, Nan; Guan, Shengxi; Foster, Jeremy M; Corrêa, Ivan R; Loose, Matthew; Dixon, James E; Sottile, Virginie; Johnson, Andrew D; Ruzov, Alexey

2014-06-12

107

Paper Mache Dinosaurs  

NSDL National Science Digital Library

In this activity (located on page 6 of PDF), learners observe and reproduce the distinctive physical features (i.e. plates, sharp spikes, long necks, deep jaws, claws) of their favorite dinosaurs. Learners construct their own dinosaurs out of recycled objects and using paper mache techniques. Learners also document and display their dinosaurs.

Museum, Chicago C.

2011-01-01

108

Digging into Dinosaurs.  

ERIC Educational Resources Information Center

This four-week unit of study for grades 1-3 provides information and activities on 17 different dinosaurs. A 21-item pre- and post-test and a brief history of dinosaurs precede descriptions and full-page drawings of the following dinosaurs: (1) giant plant-eaters (brachiosaurus, brontosaurus, and diplodocus); (2) giant meat-eaters (allosaurus,…

Oleson, Barb

109

Concise review: androgen receptor differential roles in stem/progenitor cells including prostate, embryonic, stromal, and hematopoietic lineages.  

PubMed

Stem/progenitor (S/P) cells are special types of cells that have the ability to generate tissues throughout their entire lifetime and play key roles in the developmental process. Androgen and the androgen receptor (AR) signals are the critical determinants in male gender development, suggesting that androgen and AR signals might modulate the behavior of S/P cells. In this review, we summarize the AR effects on the behavior of S/P cells, including self-renewal, proliferation, apoptosis, and differentiation in normal S/P cells, as well as proliferation, invasion, and self-renewal in prostate cancer S/P cells. AR plays a protective role in the oxidative stress-induced apoptosis in embryonic stem cells. AR inhibits the self-renewal of embryonic stem cells, bone marrow stromal cells, and prostate S/P cells, but promotes their differentiation except for adipogenesis. However, AR promotes the proliferation of hematopoietic S/P cells and stimulates hematopoietic lineage differentiation. In prostate cancer S/P cells, AR suppresses their self-renewal, metastasis, and invasion. Together, AR differentially influences the characteristics of normal S/P cells and prostate cancer S/P cells, and targeting AR might improve S/P cell transplantation therapy, especially in embryonic stem cells and bone marrow stromal cells. PMID:24740898

Huang, Chiung-Kuei; Luo, Jie; Lee, Soo Ok; Chang, Chawnshang

2014-09-01

110

Dinosaurs 2: What Were Dinosaurs Like ?  

NSDL National Science Digital Library

This Science NetLinks lesson is the second of a two-part series on dinosaurs. Activities and discussions in this lesson revolve around comparing and contrasting dinosaurs to animals with which students are familiar. Students consider likenesses and differences through researching various questions and documenting their findings.

Science Netlinks;

2004-04-16

111

Intermittent electrical stimuli for guidance of human mesenchymal stem cell lineage commitment towards neural-like cells on electroconductive substrates.  

PubMed

In the context of the role of multiple physical factors in dictating stem cell fate, the present paper demonstrates the effectiveness of the intermittently delivered external electric field stimulation towards switching the stem cell fate to specific lineage, when cultured in the absence of biochemical growth factors. In particular, our findings present the ability of human mesenchymal stem cells (hMSCs) to respond to the electric stimuli by adopting extended neural-like morphology on conducting polymeric substrates. Polyaniline (PANI) is selected as the model system to demonstrate this effect, as the electrical conductivity of the polymeric substrates can be systematically tailored over a broad range (10(-9) to 10 S/cm) from highly insulating to conducting by doping with varying concentrations (10(-5) to 1 m) of HCl. On the basis of the culture protocol involving the systematic delivery of intermittent electric field (dc) stimulation, the parametric window of substrate conductivity and electric field strength was established to promote significant morphological extensions, with minimal cellular damage. A time dependent morphological change in hMSCs with significant filopodial elongation was observed after 7 days of electrically stimulated culture. Concomitant with morphological changes, a commensurate increase in the expression of neural lineage commitment markers such as nestin and ?III tubulin was recorded from hMSCs grown on highly conducting substrates, as revealed from the mRNA expression analysis using Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) as well as by immune-fluorescence imaging. Therefore, the present work establishes the key role of intermittent and systematic delivery of electric stimuli as guidance cues in promoting neural-like differentiation of hMSCs, when grown on electroconductive substrates. PMID:24816362

Thrivikraman, Greeshma; Madras, Giridhar; Basu, Bikramjit

2014-08-01

112

Supersize That Dinosaur  

NSDL National Science Digital Library

In this activity, learners explore the size and scale of dinosaurs. Learners listen to "The Littlest Dinosaurs" by Bernard Most. Then, learners estimate the size of a Triceratops and T. rex by measuring and comparing the dinosaurs to known objects. Learners also use a hallway or go outdoors to create a full-size depiction of scale of the dinosaurs by predicting and measuring how many learners would have to lie across the ground head to foot to match the size of the two dinosaurs. This activity is featured on page 18 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

113

PRE-TRANSPLANTATION SPECIFICATION OF STEM CELLS TO CARDIAC LINEAGE FOR REGENERATION OF CARDIAC TISSUE  

PubMed Central

Myocardial infarction (MI) is a lead cause of mortality in the Western world. Treatment of acute MI is focused on restoration of antegrade flow which inhibits further tissue loss, but does not restore function to damaged tissue. Chronic therapy for injured myocardial tissue involves medical therapy that attempts to minimize pathologic remodeling of the heart. End stage therapy for chronic heart failure (CHF) involves inotropic therapy to increase surviving cardiac myocyte function or mechanical augmentation of cardiac performance. Not until the point of heart transplantation, a limited resource at best, does therapy focus on the fundamental problem of needing to replace injured tissue with new contractile tissue. In this setting, the potential for stem cell therapy has garnered significant interest for its potential to regenerate or create new contractile cardiac tissue. While to date adult stem cell therapy in clinical trials has suggested potential benefit, there is waning belief that the approaches used to date lead to regeneration of cardiac tissue. As the literature has better defined the pathways involved in cardiac differentiation, preclinical studies have suggested that stem cell pretreatment to direct stem cell differentiation prior to stem cell transplantation may be a more efficacious strategy for inducing cardiac regeneration. Here we review the available literature on pre-transplantation conditioning of stem cells in an attempt to better understand stem cell behavior and their readiness in cell-based therapy for myocardial regeneration. PMID:19184567

Mayorga, Maritza; Finan, Amanda; Penn, Marc

2009-01-01

114

Pre-transplantation specification of stem cells to cardiac lineage for regeneration of cardiac tissue.  

PubMed

Myocardial infarction (MI) is a lead cause of mortality in the Western world. Treatment of acute MI is focused on restoration of antegrade flow which inhibits further tissue loss, but does not restore function to damaged tissue. Chronic therapy for injured myocardial tissue involves medical therapy that attempts to minimize pathologic remodeling of the heart. End stage therapy for chronic heart failure (CHF) involves inotropic therapy to increase surviving cardiac myocyte function or mechanical augmentation of cardiac performance. Not until the point of heart transplantation, a limited resource at best, does therapy focus on the fundamental problem of needing to replace injured tissue with new contractile tissue. In this setting, the potential for stem cell therapy has garnered significant interest for its potential to regenerate or create new contractile cardiac tissue. While to date adult stem cell therapy in clinical trials has suggested potential benefit, there is waning belief that the approaches used to date lead to regeneration of cardiac tissue. As the literature has better defined the pathways involved in cardiac differentiation, preclinical studies have suggested that stem cell pretreatment to direct stem cell differentiation prior to stem cell transplantation may be a more efficacious strategy for inducing cardiac regeneration. Here we review the available literature on pre-transplantation conditioning of stem cells in an attempt to better understand stem cell behavior and their readiness in cell-based therapy for myocardial regeneration. PMID:19184567

Mayorga, Maritza; Finan, Amanda; Penn, Marc

2009-03-01

115

Dinosaur energetics: setting the bounds on feasible physiologies and ecologies.  

PubMed

The metabolic status of dinosaurs has long been debated but remains unresolved as no consistent picture has emerged from a range of anatomical and isotopic evidence. Quantitative analysis of dinosaur energetics, based on general principles applicable to all vertebrates, shows that many features of dinosaur lifestyle are compatible with a physiology similar to that of extant lizards, scaled up to dinosaur body masses and temperatures. The analysis suggests that sufficient metabolic scope would have been available to support observed dinosaur growth rates and allow considerable locomotor activity, perhaps even migration. Since at least one dinosaur lineage evolved true endothermy, this study emphasizes there was no single dinosaur physiology. Many small theropods were insulated with feathers and appear to have been partial or full endotherms. Uninsulated small taxa, and all juveniles, presumably would have been ectothermic, with consequent diurnal and seasonal variations in body temperature. In larger taxa, inertial homeothermy would have resulted in warm and stable body temperatures but with a basal metabolism significantly below that of extant mammals or birds of the same size. It would appear that dinosaurs exhibited a range of metabolic levels to match the broad spectrum of ecological niches they occupied. PMID:23933721

Clarke, Andrew

2013-09-01

116

PI3 K\\/Akt\\/mTOR-mediated translational control regulates proliferation and differentiation of lineage-restricted RoSH stem cell lines  

Microsoft Academic Search

BACKGROUND: We have previously derived highly similar lineage-restricted stem cell lines, RoSH and E-RoSH cell lines from mouse embryos and CD9hi SSEA-1- differentiated mouse embryonic stem cells, respectively. These cell lines are not pluripotent and differentiate readily into endothelial cells in vitro and in vivo. RESULTS: We investigated the signaling pathway that maintains proliferation of these cells in an undifferentiated

Jianwen Que; Qizhou Lian; Reida M El Oakley; Bing Lim; Sai-Kiang Lim

2007-01-01

117

The adipose-derived lineage-negative cells are enriched mesenchymal stem cells and promote limb ischemia recovery in mice.  

PubMed

White adipose tissue (WAT) is a very attractive source of mesenchymal stem cells (MSCs) because of its availability and ease of harvest. However, the current method of isolating adipose tissue-derived MSCs often relies on the adhesiveness of the cultured stromal-vascular fraction (SVF). Unfortunately, the SVF is a heterogeneous cell population containing many cell types, including adipocyte precursor cells, endothelial cells, pericytes, multipotent MSCs, erythrocytes, and hematopoietic cells. Here we systematically characterized the adipose tissue-derived lineage-negative (Lin(-)) cell population using various surface markers and a set of cell proliferation and differentiation assays. We demonstrate clearly that the Lin(-) cell population represents enriched MSCs, which were identified by their high expression of MSC surface markers, and that these cells are a robust population with a vigorous growth capability and delayed aging. This cell population also demonstrated a much higher capacity for differentiation into osteogenic, chondrogenic and adipogenic cell lineages related to MSCs than did the SVF. These cells promoted recovery from limb ischemia, likely via production of vascular endothelial growth factor, an angiogenic factor. Our study demonstrates that Lin(-) cells are enriched in MSCs and provides a reliable method for isolating purer MSCs than SVF cells from the WAT, especially for obtaining fresh MSCs for clinical applications. In summary, this study identified a new, reliable method for enrichment of WAT MSCs with regenerative repairing features. PMID:24083854

Qin, Yiren; Zhou, Peijie; Zhou, Chikai; Li, Jinsong; Gao, Wei-Qiang

2014-02-15

118

The histone H2A deubiquitinase Usp16 regulates embryonic stem cell gene expression and lineage commitment  

PubMed Central

Polycomb Repressive Complex 1 and histone H2A ubiquitination (ubH2A) contribute to embryonic stem cell (ESC) pluripotency by repressing lineage-specific gene expression. However, whether active deubiquitination co-regulates ubH2A levels in ESCs and during differentiation is not known. Here we report that Usp16, a histone H2A deubiquitinase, regulates H2A deubiquitination and gene expression in ESCs, and importantly, is required for ESC differentiation. Usp16 knockout is embryonic lethal in mice, but does not affect ESC viability or identity. Usp16 binds to the promoter regions of a large number of genes in ESCs, and Usp16 binding is inversely correlated with ubH2A levels, and positively correlates with gene expression levels. Intriguingly, Usp16?/? ESCs fail to differentiate due to ubH2A-mediated repression of lineage-specific genes. Finally, Usp16, but not a catalytically inactive mutant, rescues the differentiation defects of Usp16?/? ESCs. Therefore, this study identifies Usp16 and H2A deubiquitination as critical regulators of ESC gene expression and differentiation. PMID:24784029

Yang, Wei; Lee, Yun-Hwa; Jones, Amanda E.; Woolnough, Jessica L.; Zhou, Dewang; Dai, Qian; Wu, Qiang; Giles, Keith E.; Townes, Tim M.; Wang, Hengbin

2014-01-01

119

Activation of GSK3? by Sirt2 Is Required for Early Lineage Commitment of Mouse Embryonic Stem Cell  

PubMed Central

Sirt2, a member of the NAD+-dependent protein deacetylase family, is increasingly recognized as a critical regulator of the cell cycle, cellular necrosis and cytoskeleton organization. However, its role in embryonic stem cells (ESCs) remains unclear. Here we demonstrate that Sirt2 is up-regulated during RA (retinoic acid)-induced and embryoid body (EB) differentiation of mouse ESCs. Using lentivirus-mediated shRNA methods, we found that knockdown of Sirt2 compromises the differentiation of mouse ESCs into ectoderm while promoting mesoderm and endoderm differentiation. Knockdown of Sirt2 expression also leads to the activation of GSK3? through decreased phosphorylation of the serine at position 9 (Ser9) but not tyrosine at position 216 (Tyr216). Moreover, the constitutive activation of GSK3? during EB differentiation mimics the effect of Sirt2 knockdown, while down-regulation of GSK3? rescues the effect of Sirt2 knockdown on differentiation. In contrast to the effect on lineage differentiation, Sirt2 knockdown and GSK3? up-regulation do not change the self-renewal state of mouse ESCs. Overall, our report reveals a new function for Sirt2 in regulating the proper lineage commitment of mouse ESCs. PMID:24204656

Guo, Xudong; Chen, Long; Wang, Guiying; Xu, Yanxin; Kang, Jiuhong

2013-01-01

120

Ethanol Diverts Early Neuronal Differentiation Trajectory of Embryonic Stem Cells by Disrupting the Balance of Lineage Specifiers  

PubMed Central

Background Ethanol is a toxin responsible for the neurodevelopmental deficits of Fetal Alcohol Spectrum Disorders (FASD). Recent evidence suggests that ethanol modulates the protein expression of lineage specifier transcription factors Oct4 (Pou5f1) and Sox2 in early stages of mouse embryonic stem (ES) cell differentiation. We hypothesized that ethanol induced an imbalance in the expression of Oct4 and Sox2 in early differentiation, that dysregulated the expression of associated and target genes and signaling molecules and diverted cells from neuroectodermal (NE) formation. Methodology/Principal Findings We showed modulation by ethanol of 33 genes during ES cell differentiation, using high throughput microfluidic dynamic array chips measuring 2,304 real time quantitative PCR assays. Based on the overall gene expression dynamics, ethanol drove cells along a differentiation trajectory away from NE fate. These ethanol-induced gene expression changes were observed as early as within 2 days of differentiation, and were independent of cell proliferation or apoptosis. Gene expression changes were correlated with fewer ?III-tubulin positive cells of an immature neural progenitor phenotype, as well as a disrupted actin cytoskeleton were observed. Moreover, Tuba1a and Gapdh housekeeping genes were modulated by ethanol during differentiation and were replaced by a set of ribosomal genes with stable expression. Conclusions/Significance These findings provided an ethanol-response gene signature and pointed to the transcriptional dynamics underlying lineage imbalance that may be relevant to FASD phenotype. PMID:23724002

Sánchez-Alvarez, Rosa; Gayen, Saurabh; Vadigepalli, Rajanikanth; Anni, Helen

2013-01-01

121

Radiolabeling and In Vivo Imaging of Transplanted Renal Lineages Differentiated from Human Embryonic Stem Cells in Fetal Rhesus Monkeys  

PubMed Central

Purpose The goals of this study were to optimize radiolabeling of renal lineages differentiated from human embryonic stem (hES) cells and use noninvasive imaging (positron emission tomography (PET) and bioluminescence imaging (BLI)) to detect the cells in fetal monkeys post-transplant. Procedures hES cells expressing firefly luciferase (5×106) were radiolabeled with the optimized concentration of 10 ?Ci/ml 64Cu-PTSM then transplanted under ultrasound guidance into early second trimester fetal monkey kidneys. Fetuses were imaged in utero with PET and tissues collected for analysis 3 days post-transplant. Fetal kidneys were imaged ex vivo (PET and BLI) post-tissue harvest, and serial kidney sections were assessed by PCR for human-specific DNA sequences, fluorescent in situ hybridization (FISH) for human-specific centromere probes, and immunohistochemistry (IHC) to assess engrafted cells. Results Transplanted cells were readily imaged in vivo and identified at the site of injection; tissue analyses confirmed the imaging findings. Using a semi-quantitative method, one in approximately 650 cells in the kidney was shown to be of human origin by PCR and FISH. Conclusions These studies suggest that hES cells differentiated toward renal lineages can be effectively radiolabeled, transplanted into fetal monkey kidneys under ultrasound guidance, monitored with PET post-transplant, and identified by PET, BLI, PCR, FISH, and IHC post-tissue harvest. PMID:21479709

Tarantal, Alice F.; Lee, C. Chang I.; Batchelder, Cynthia A.; Christensen, Jared E.; Prater, Daniel; Cherry, Simon R.

2014-01-01

122

Effects of Ionizing Radiation on Human Adipose Derived Mesenchymal Stem Cells and their Differentiation towards the Osteoblastic Lineage  

NASA Astrophysics Data System (ADS)

Radiation exposure and musculoskeletal disuse are among the major challenges during space missions. Astronauts face the problem to lose bone calcium due to uncoupling of bone formation and resorption. Bone forming osteoblasts can be derived from the undifferentiated mesenchymal stem cell compartment (MSC). In this study, the ability of human adipose tissue derived stem cells (ATSC) to differentiate into the osteoblastic lineage was examined after radiation exposure in presence of medium supplementation with osteogenic additives (ß-glycerophosphate, ascorbic acid and dexamethasone). The SAOS-2 cell line (human osteosarcoma cell line) was used as control for osteoblastic differentiation. Changes in cellular morphology, cell cycle progression, as well as cellular radiation sensitivity were characterized after ionizing radiation exposure with X-rays and heavy ions (Ti). Rapidly proliferating SAOS-2 cells are less radiation-sensitive than slowly proliferating ATSC cells after X-ray (CFA: dose effect curves show D0 values of 1 Gy and 0.75 Gy for SAOS-2 and ATSC, respectively) exposure. Heavy ion (Ti) exposure resulted in a greater extent of cells accumulating in the G2/M phase of the cell cycle in a dose-dependent manner when compared to X-ray exposure. Differentiation of cells towards the osteoblastic lineage was quantified by hydroxyapatite (HA) deposition using Lonza OsteoImageTM mineralization assay. The deposition of HA after X- and Ti-irradiation for highly proliferating SAOS-2 cells showed a dose-dependent time delay while slowly proliferating ATSC showed no effect from radiation exposure. More detailed investigation is required to reveal the radiation dependent mechanism of bone loss in astronauts.

Konda, Bikash; Baumstark-Khan, Christa; Hellweg, Christine; Reitz, Guenther; Lau, Patrick

123

Lineage-specific transformation after differentiation of multipotential murine stem cells containing a human oncogene.  

PubMed Central

We transfected the human EJ bladder carcinoma oncogene (Ha-rasEJ-1) into multipotential embryonal carcinoma cell line P19. The transgenic P19(ras+) cells expressed high levels of both the mRNA and the p21EJ protein derived from the oncogene. When cultured in the presence of retinoic acid, P19(ras+) cells differentiated and developed into the same spectrum of differentiated cell types as the parental P19 cells (namely, neurons, astrocytes, and fibroblast-like cells). Thus, it seems unlikely that the Ha-ras-1 proto-oncogene product plays a role in initiation of differentiation or in the choice of differentiated cell lineage. Most of the P19(ras+)-derived differentiated cells contained relatively low levels of p21EJ and were nontransformed, whereas certain cells with fibroblast-like morphology continued to express the Ha-rasEJ-1 gene at high levels and were transformed (i.e., immortal and anchorage independent). Fibroblasts derived from P19 cells did not become transformed following transfection of the Ha-rasEJ-1 oncogene, suggesting that transformation of the fibroblast cells only occurred if the oncogene was present and expressed during the early stages of the developmental lineage. Images PMID:3785155

Bell, J C; Jardine, K; McBurney, M W

1986-01-01

124

Calcium Dependent CAMTA1 in Adult Stem Cell Commitment to a Myocardial Lineage  

Microsoft Academic Search

The phenotype of somatic cells has recently been found to be reversible. Direct reprogramming of one cell type into another has been achieved with transduction and over expression of exogenous defined transcription factors emphasizing their role in specifying cell fate. To discover early and novel endogenous transcription factors that may have a role in adult-derived stem cell acquisition of a

Barbara Muller-Borer; Gwyn Esch; Rob Aldina; Woohyun Woon; Raymond Fox; Nenad Bursac; Sylvia Hiller; Nobuyuo Maeda; Neal Shepherd; Jian Ping Jin; Mary Hutson; Page Anderson; Margaret L. Kirby; Nadia N. Malouf

2012-01-01

125

Compare Dinosaur Body Parts  

NSDL National Science Digital Library

In this activity, learners explore the size and scale of dinosaurs. Learners listen to "The Littlest Dinosaurs" by Bernard Most to learn about the different sizes of dinosaurs. Then, learners create a chart of measurements that compare the sizes of the body parts of a T. rex, Triceratops, the learner, and their partner. Learners also convert the measurements into centimeters and meters. This activity is featured on pp. 20-21 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

126

Create a Dinosaur Name  

NSDL National Science Digital Library

In this activity, learners explore how dinosaurs are named and what their names mean. Learners listen to "The Littlest Dinosaurs" by Bernard Most. Then, learners decode real and imaginary dinosaur names by sliding paper strips featuring Latin and Greek words through three openings in a T. rex skull drawing. This activity is featured on page 11 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

127

Those Fussy Dinosaurs!  

NSDL National Science Digital Library

This lesson introduces students to the idea that animals prefer certain types of habitats over others and, in fact, cannot live in places that are too different from what they prefer. In this case they will focus on dinosaurs. They will learn about the types of habitats and climates scientists believe dinosaurs tended to prefer and will conclude by drawing background scenes to use in a toy dinosaur home.

128

Dinosaur Planet video gallery  

NSDL National Science Digital Library

Despite the long loading times and annoying advertisements, there are a variety of worthwhile Flash and Windows media animations. As might be expected, the animations tend to stress the flashy, violent aspects of dinosaurs, like velociraptor attacks but there are also clips showing dinosaur eggs hatching, dinosaur locomotion, and even an interview with a paleontologist. A fast connection is a must to properly view this site.

Channel, Discovery

129

CXCL12/CXCR4 signaling in the osteoblast regulates the mesenchymal stem cell and osteoclast lineage populations.  

PubMed

The chemokine CXCL12 and its receptor CXCR4 play a key role in regulation of hematopoietic stem cells and cell migratory function during morphogenesis. Osteoblasts express both the ligand and the receptor, but little is known about the role of CXCL12-CXCR4 signaling in maintaining skeletal homeostasis. Using Cre-Lox technology to delete CXCR4 in mature osteoblasts in mice, we show here a significant decrease in bone mass and alterations in cancellous bone structure. CXCR4 gene ablation increased the number of colony-forming units (CFU), CFU-positive for alkaline phosphatase (CFU-AP(+)), and mineralizing nodules in bone marrow stromal cell (BMSC) cultures. The adipocyte precursor population decreased in BMSCs harvested from the KO animals. The nonadherent population of BMSCs harvested from the long bone diaphysis of KO animals formed more osteoclasts, a finding that was associated with increased circulatory levels of pyridinoline, a marker of bone resorption. Our data show that osteoblast-specific CXCR4 deletion has profound effects on the mesenchymal stem cell pool and allocation to the osteoblastic and adipocytic cell lineages. They also show that CXCL12/CXCR4 signaling in the mature osteoblast can feedback to regulate the osteoclast precursor pool size and play a multifunctional role in regulating bone formation and resorption. PMID:23704087

Shahnazari, Mohammad; Chu, Vivian; Wronski, Thomas J; Nissenson, Robert A; Halloran, Bernard P

2013-09-01

130

Directed differentiation of induced pluripotent stem cells into chondrogenic lineages for articular cartilage treatment  

PubMed Central

In recent years, increases in the number of articular cartilage injuries caused by environmental factors or pathological conditions have led to a notable rise in the incidence of premature osteoarthritis. Osteoarthritis, considered a disease of civilization, is the leading cause of disability. At present, standard methods for treating damaged articular cartilage, including autologous chondrocyte implantation or microfracture, are short-term solutions with important side effects. Emerging treatments include the use of induced pluripotent stem cells, a technique that could provide a new tool for treatment of joint damage. However, research in this area is still early, and no optimal protocol for transforming induced pluripotent stem cells into chondrocytes has yet been established. Developments in our understanding of cartilage developmental biology, together with the use of modern technologies in the field of tissue engineering, provide an opportunity to create a complete functional model of articular cartilage. PMID:25383175

Lach, Michal; Richter, Magdalena; Pawlicz, Jaroslaw; Suchorska, Wiktoria M

2014-01-01

131

Generation of purified neural precursors from embryonic stem cells by lineage selection  

Microsoft Academic Search

Mouse embryonic stem (ES) cells are non-transformed cell lines derived directly from the pluripotent founder tissue in the mouse embryo, the epiblast [1–3]. Aggregation of ES cells triggers the generation of a diverse array of cell types, including neuronal cells [4–7]. This capacity for multilineage differentiation is retained during genetic manipulation and clonal expansion [8]. In principle, therefore, ES cells

Meng Li; Larysa Pevny; Robin Lovell-Badge; Austin Smith

1998-01-01

132

Multi-Organ, Multi-Lineage Engraftment by a Single Bone Marrow-Derived Stem Cell  

Microsoft Academic Search

Purification of rare hematopoietic stem cell(s) (HSC) to homogeneity is required to study their self-renewal, differentiation, phenotype, and homing. Long-term repopulation (LTR) of irradiated hosts and serial transplantation to secondary hosts represent the gold standard for demonstrating self-renewal and differentiation, the defining properties of HSC. We show that rare cells that home to bone marrow can LTR primary and secondary

Diane S. Krause; Neil D. Theise; Octavian Henegariu; Sonya Hwang; Rebekah Gardner; Sara Neutzel; Saul J. Sharkis

2001-01-01

133

The Dinosaur Name Game  

NSDL National Science Digital Library

In this classroom activity, middle school students explore the Greek and Latin root words used to create dinosaur names. The activity opens with background information for teachers about how dinosaurs are named. As a class, students explore the Greek and Latin roots of the words photograph, terrace and other familiar terms. Working individually, students complete a worksheet that challenges them to translate the meaning of seven dinosaurs' names. Then, working in pairs, students create their own dinosaur; name it; and describe how it moves, what it eats, how it raises it young, and how it behaves.

134

Enhanced Differentiation of Adult Bone Marrow-Derived Stem Cells to Liver Lineage in Aggregate Culture  

PubMed Central

Hepatocyte-like cells derived from stem cells hold great potential for clinical and pharmaceutical applications, including high-throughput drug toxicity screening. We report a three-dimensional aggregate culture system for the directed differentiation of adult rat bone marrow-derived stem cells, rat multipotent adult progenitor cells, to hepatocyte-like cells. Compared to adherent monolayer cultures, differentiation in the aggregate culture system resulted in significantly higher expression level of liver-specific transcripts, including an increased albumin mRNA level, and higher levels of albumin and urea secretion. This coincides with the presence of significantly more cells that express intracellular albumin at levels found in primary hepatocytes. The differentiated cell aggregates exhibited cytochrome P450-mediated ethoxyresorufin-O-dealkylation and pentoxyresorufin-O-dealkylation activity. Consistent with these increased mature functions, cells within the aggregates were shown to have many ultrastructural features of mature hepatocytes by transmission electron microscopy. With the scalability of the aggregate culture system and the enhanced differentiation capability, this system may facilitate translation of generating hepatocytes from stem cells to technology. PMID:21548835

Subramanian, Kartik; Owens, Derek Jason; O'Brien, Timothy D.; Verfaillie, Catherine M.

2011-01-01

135

Hypoxia and lineage specification of cell line-derived colorectal cancer stem cells  

PubMed Central

Hypoxia is an important regulator of normal and cancer stem cell (CSC) differentiation. Colorectal CSCs from SW1222, LS180, and CCK81 colorectal cancer-derived cell lines are able to differentiate into complex 3D lumen-containing structures in normoxia, whereas in hypoxia, they form undifferentiated dense colonies that have reduced expression of the enterocyte differentiation marker CDX1, lack goblet cell formation, and have increased expression of BMI1 and activated Notch1. Hypoxia increases the clonogenicity of CSCs, which is cumulative as each round of hypoxia enriches for more CSCs. The hypoxic phenotype is reversible, because cells from hypoxic-dense colonies are able to reform differentiated structures when regrown in normoxia. We show that CDX1 is able to stimulate the generation of lumens even in hypoxia and has a negative feedback on BMI1 expression. Knockdown of CDX1 reduces lumen formation but does not affect goblet cell formation, suggesting that enterocytes and goblet cells form from different progenitor cells. Notch inhibition by dibenzazepine (DBZ) allowed CSCs to form goblet cells in both normoxia and hypoxia. Finally, we show that Hif1?, but not CA9, is an important mediator of the effects of hypoxia on the clonogenicity and differentiation of CSCs. In summary, hypoxia maintains the stem-like phenotype of colorectal cell line-derived CSCs and prevents differentiation of enterocytes and goblet cells by regulating CDX1 and Notch1, suggesting that this regulation is an important component of how hypoxia controls the switch between stemness and differentiation in CSCs. PMID:21368208

Yeung, Trevor M.; Gandhi, Shaan C.; Bodmer, Walter F.

2011-01-01

136

Activated charcoal composite biomaterial promotes human embryonic stem cell differentiation toward neuronal lineage.  

PubMed

Transplantation of biomaterial scaffolds encasing human embryonic stem cells (hESCs) has been proposed as a clinical therapy for various neurological lesions and disorders. In light of recent developments, artificially synthesized carbon-based biomaterials such as carbon nanotubes and graphene have demonstrated feasibility in supporting stem cell attachment and differentiation. However, the applicability is significantly hampered by evidence of nanotoxic effects on multiple cell types. Thus, an emergent drive for an innovative carbonaceous biomaterial calls for a safer platform with comparable advantageous characteristics. Here, we showed for the first time, a natural coal-based activated charcoal (AC) composite biosubstrate can support and promote neuronal differentiation in hESCs. The bio-friendly AC composite biomatrices resulted in more matured neuron-like cells. Both of axonal length and density were at least twice as long and abundant, respectively, when compared with control groups. A functional assay demonstrated that the derived neuron-like cells responded to depolarization-dependent synaptic recycling and may contain active synapses. In addition, the AC composite substrate can serve to concentrate growth factors and cell adhesion proteins, further encouraging attachment and hESC differentiation. Moreover, the AC composite biomaterial can potentially be economically manufactured as implantable three-dimensional bioscaffolds, facilitating the regeneration of damaged neural and other tissues. PMID:22623371

Chen, Eric Y T; Wang, Yung-Chen; Mintz, Alexander; Richards, Alan; Chen, Chi-Shuo; Lu, David; Nguyen, Thien; Chin, Wei-Chun

2012-08-01

137

Concise review: skeletal muscle stem cells and cardiac lineage: potential for heart repair.  

PubMed

Valuable and ample resources have been spent over the last two decades in pursuit of interventional strategies to treat the unmet demand of heart failure patients to restore myocardial structure and function. At present, it is clear that full restoration of myocardial structure and function is outside our reach from both clinical and basic research studies, but it may be achievable with a combination of ongoing research, creativity, and perseverance. Since the 1990s, skeletal myoblasts have been extensively investigated for cardiac cell therapy of congestive heart failure. Whereas the Myoblast Autologous Grafting in Ischemic Cardiomyopathy (MAGIC) trial revealed that transplanted skeletal myoblasts did not integrate into the host myocardium and also did not transdifferentiate into cardiomyocytes despite some beneficial effects on recipient myocardial function, recent studies suggest that skeletal muscle-derived stem cells have the ability to adopt a cardiomyocyte phenotype in vitro and in vivo. This brief review endeavors to summarize the importance of skeletal muscle stem cells and how they can play a key role to surpass current results in the future and enhance the efficacious implementation of regenerative cell therapy for heart failure. PMID:24371329

Hassan, Narmeen; Tchao, Jason; Tobita, Kimimasa

2014-02-01

138

Digging into Dinosaurs.  

ERIC Educational Resources Information Center

Ranger Rick's NatureScope is a creative education series dedicated to inspiring in children an understanding and appreciation of the natural world while developing the skills they will need to make responsible decisions about the environment. Contents are organized into the following sections: (1) "What Makes a Dinosaur a Dinosaur?," including…

Braus, Judy, Ed.

1989-01-01

139

Dinosaur Footprints & Fossils  

NSDL National Science Digital Library

In this activity, early learners simulate fossil prints in play dough or clay. Using plastic dinosaur feet to make footprints on their âmudâ (much as dinosaurs walked around their habitat) and harvest items (leaves, corn, twigs, acorns) to make impressions, learners simulate fossil prints. This resource includes open-ended discussion questions to encourage reflection.

Omsi

2004-01-01

140

Paleobiology of Herbivorous Dinosaurs  

NASA Astrophysics Data System (ADS)

Herbivorous dinosaurs were abundant, species-rich components of Late Triassic-Cretaceous terrestrial ecosystems. Obligate high-fiber herbivory evolved independently on several occasions within Dinosauria, through the intermediary step of omnivory. Anatomical character complexes associated with this diet exhibit high levels of convergence and morphological disparity, and may have evolved by correlated progression. Dinosaur faunas changed markedly during the Mesozoic, from early faunas dominated by taxa with simple, uniform feeding mechanics to Cretaceous biomes including diverse sophisticated sympatric herbivores; the environmental and biological drivers causing these changes remain unclear. Isotopic, taphonomic, and anatomical evidence implies that niche partitioning reduced competition between sympatric herbivores, via morphological differentiation, dietary preferences, and habitat selection. Large body size in dinosaur herbivores is associated with low plant productivity, and gave these animals prominent roles as ecosystem engineers. Although dinosaur herbivores lived through several major events in floral evolution, there is currently no evidence for plant-dinosaur coevolutionary interactions.

Barrett, Paul M.

2014-05-01

141

No gastric mill in sauropod dinosaurs: new evidence from analysis of gastrolith mass and function in ostriches  

PubMed Central

Polished pebbles occasionally found within skeletons of giant herbivorous sauropod dinosaurs are very likely to be gastroliths (stomach stones). Here, we show that based on feeding experiments with ostriches and comparative data for relative gastrolith mass in birds, sauropod gastroliths do not represent the remains of an avian-style gastric mill. Feeding experiments with farm ostriches showed that bird gastroliths experience fast abrasion in the gizzard and do not develop a polish. Relative gastrolith mass in sauropods (gastrolith mass much less than 0.1% of body mass) is at least an order of magnitude less than that in ostriches and other herbivorous birds (gastrolith mass approximates 1% of body mass), also arguing against the presence of a gastric mill in sauropods. Sauropod dinosaurs possibly compensated for their limited oral processing and gastric trituration capabilities by greatly increasing food retention time in the digestive system. Gastrolith clusters of some derived theropod dinosaurs (oviraptorosaurs and ornithomimosaurs) compare well with those of birds, suggesting that the gastric mill evolved in the avian stem lineage. PMID:17254987

Wings, Oliver; Sander, P. Martin

2006-01-01

142

Red Ginseng Extract Facilitates the Early Differentiation of Human Embryonic Stem Cells into Mesendoderm Lineage  

PubMed Central

Human embryonic stem cells (hESCs) have capacities to self-renew and differentiate into all cell types in vitro. Red ginseng (RG) is known to have a wide range of pharmacological effects in vivo; however, the reports on its effects on hESCs are few. In this paper, we tried to demonstrate the effects of RG on the proliferation and differentiation of hESCs. Undifferentiated hESCs, embryoid bodies (EBs), and hESC-derived cardiac progenitors (CPs) were treated with RG extract at 0.125, 0.25, and 0.5?mg/mL. After treatment of undifferentiated hESCs from day 2 to day 6 of culture, BrdU labeling showed that RG treatment increased the proliferation of hESCs, and the expression of Oct4 and Nanog was increased in RG-treated group. To find out the effects of RG on early differentiation stage cells, EBs were treated with RG extract for 10 days and attached for further differentiation. Immunostaining for three germ layer markers showed that RG treatment increased the expressions of Brachyury and HNF3? on EBs. Also, RG treatment increased the expression of Brachyury in early-stage and of Nkx2.5 in late-stage hESC-derived CPs. These results demonstrate facilitating effects of RG extract on the proliferation and early differentiation of hESC. PMID:20924497

Kim, Yoon Young; Ku, Seung-Yup; Rosenwaks, Zev; Liu, Hung Ching; Oh, Sun Kyung; Moon, Shin Yong; Choi, Young Min

2011-01-01

143

Transdifferentiation of human periodontal ligament stem cells into pancreatic cell lineage.  

PubMed

Human periodontal ligament-derived stem cells (PDLSCs) demonstrate self-renewal capacity and multilineage differentiation potential. In this study, we investigated the transdifferentiation potential of human PDLSCs into pancreatic islet cells. To form three-dimensional (3D) clusters, PDLSCs were cultured in Matrigel with media containing differentiation-inducing agents. We found that after 6?days in culture, PDLSCs underwent morphological changes resembling pancreatic islet-like cell clusters (ICCs). The morphological characteristics of PDLSC-derived ICCs were further assessed using scanning electron microscopy analysis. Using reverse transcription-polymerase chain reaction analysis, we found that pluripotency genes were downregulated, whereas early endoderm and pancreatic differentiation genes were upregulated, in PDLSC-derived ICCs compared with undifferentiated PDLSCs. Furthermore, we found that PDLSC-derived ICCs were capable of secreting insulin in response to high concentrations of glucose, validating their functional differentiation into islet cells. Finally, we also performed dithizone staining, as well as immunofluorescence assays and fluorescence-activated cell sorting analysis for pancreatic differentiation markers, to confirm the differentiation status of PDLSC-derived ICCs. These results demonstrate that PDLSCs can transdifferentiate into functional pancreatic islet-like cells and provide a novel, alternative cell population for pancreatic repair. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25187163

Lee, Jeong Seok; An, Seong Yeong; Kwon, Il Keun; Heo, Jung Sun

2014-10-01

144

GEF-H1 controls focal adhesion signaling that regulates mesenchymal stem cell lineage commitment  

PubMed Central

ABSTRACT Focal adhesions (FAs) undergo maturation that culminates in size and composition changes that modulate adhesion, cytoskeleton remodeling and differentiation. Although it is well recognized that stimuli for osteogenesis of mesenchymal stem cells (MSCs) drive FA maturation, actin organization and stress fiber polarization, the extent to which FA-mediated signals regulated by the FA protein composition specifies MSC commitment remains largely unknown. Here, we demonstrate that, upon dexamethasone (osteogenic induction) treatment, guanine nucleotide exchange factor H1 (GEF-H1, also known as Rho guanine nucleotide exchange factor 2, encoded by ARHGEF2) is significantly enriched in FAs. Perturbation of GEF-H1 inhibits FA formation, anisotropic stress fiber orientation and MSC osteogenesis in an actomyosin-contractility-independent manner. To determine the role of GEF-H1 in MSC osteogenesis, we explore the GEF-H1-modulated FA proteome that reveals non-muscle myosin-II heavy chain-B (NMIIB, also known as myosin-10, encoded by MYH10) as a target of GEF-H1 in FAs. Inhibition of targeting NMIIB into FAs suppresses FA formation, stress fiber polarization, cell stiffness and osteogenic commitments in MSCs. Our data demonstrate a role for FA signaling in specifying MSC commitment. PMID:25107365

Huang, I-Husan; Hsiao, Cheng-Te; Wu, Jui-Chung; Liu, Ching-Yi; Wang, Yang-Kao; Chen, Yu-Chen; Huang, Chi-Ming; del alamo, Juan C.; Chang, Zee-Fen; Tang, Ming-Jer; Khoo, Kay-Hooi; Kuo, Jean-Cheng

2014-01-01

145

Transplantation of CD15-enriched murine neural stem cells increases total engraftment and shifts differentiation toward the oligodendrocyte lineage.  

PubMed

Neural stem cell (NSC) transplantation is a promising therapeutic approach for neurological diseases. However, only a limited number of cells can be transplanted into the brain, resulting in relatively low levels of engraftment. This study investigated the potential of using a cell surface marker to enrich a primary NSC population to increase stable engraftment in the recipient brain. NSCs were enriched from the neonatal mouse forebrain using anti-CD15 (Lewis X antigen, or SSEA-1) in a "gentle" fluorescence-activated cell sorting protocol, which yielded >98% CD15-positive cells. The CD15-positive cells differentiated into neurons, astrocytes, and oligodendrocytes in vitro, after withdrawal of growth factors, demonstrating multipotentiality. CD15-positive cells were expanded in vitro and injected bilaterally into the ventricles of neonatal mice. Cells from enriched and unenriched donor populations were found throughout the neuraxis, in both neurogenic and non-neurogenic regions. Total engraftment was similar at 7 days postinjection, but by 28 days postinjection, after brain organogenesis was complete, the survival of donor cells was significantly increased in CD15-enriched grafts over the unenriched cell grafts. The engrafted cells were heterogeneous in morphology and differentiated into all three neural lineages. Furthermore, in the CD15-enriched grafts, there was a significant shift toward differentiation into oligodendrocytes. This strategy may allow better delivery of therapeutic cells to the developing central nervous system and may be particularly useful for treating diseases involving white matter lesions. PMID:23681951

Chaubey, Sushma; Wolfe, John H

2013-06-01

146

Evidence for a Critical Role of Catecholamines for Cardiomyocyte Lineage Commitment in Murine Embryonic Stem Cells  

PubMed Central

Catecholamine release is known to modulate cardiac output by increasing heart rate. Although much is known about catecholamine function and regulation in adults, little is known about the presence and role of catecholamines during heart development. The present study aimed therefore to evaluate the effects of different catecholamines on early heart development in an in vitro setting using embryonic stem (ES) cell-derived cardiomyocytes. Effects of catecholamine depletion induced by reserpine were examined in murine ES cells (line D3, ?PIG44) during differentiation. Cardiac differentiation was assessed by immunocytochemistry, qRT-PCR, quantification of beating clusters, flow cytometry and pharmacological approaches. Proliferation was analyzed by EB cross-section measurements, while functionality of cardiomyocytes was studied by extracellular field potential (FP) measurements using microelectrode arrays (MEAs). To further differentiate between substance-specific effects of reserpine and catecholamine action via ?- and ?-receptors we proved the involvement of adrenergic receptors by application of unspecific ?- and ?-receptor antagonists. Reserpine treatment led to remarkable down-regulation of cardiac-specific genes, proteins and mesodermal marker genes. In more detail, the average ratio of ?40% spontaneously beating control clusters was significantly reduced by 100%, 91.1% and 20.0% on days 10, 12, and 14, respectively. Flow cytometry revealed a significant reduction (by 71.6%, n?=?11) of eGFP positive CMs after reserpine treatment. By contrast, reserpine did not reduce EB growth while number of neuronal cells in reserpine-treated EBs was significantly increased. MEA measurements of reserpine-treated EBs showed lower FP frequencies and weak responsiveness to adrenergic and muscarinic stimulation. Interestingly we found that developmental inhibition after ?- and ?-adrenergic blocker application mimicked developmental changes with reserpine. Using several methodological approaches our data suggest that reserpine inhibits cardiac differentiation. Thus catecholamines play a critical role during development. PMID:23936474

Lehmann, Martin; Nguemo, Filomain; Wagh, Vilas; Pfannkuche, Kurt; Hescheler, Jurgen; Reppel, Michael

2013-01-01

147

Analysis of stem cell lineage progression in the neonatal subventricular zone identifies EGFR+/NG2- cells as transit-amplifying precursors.  

PubMed

In the adult subventricular zone (SVZ), astroglial stem cells generate transit-amplifying precursors (TAPs). Both stem cells and TAPs form clones in response to epidermal growth factor (EGF). However, in vivo, in the absence of sustained EGF receptor (EGFR) activation, TAPs divide a few times before differentiating into neuroblasts. The lack of suitable markers has hampered the analysis of stem cell lineage progression and associated functional changes in the neonatal germinal epithelium. Here we purified neuroblasts and clone-forming precursors from the neonatal SVZ using expression levels of EGFR and polysialylated neural cell adhesion molecule (PSANCAM). As in the adult SVZ, most neonatal clone-forming precursors did not express the neuroglia proteoglycan 2 (NG2) but displayed characteristics of TAPs, and only a subset exhibited antigenic characteristics of astroglial stem cells. Both precursors and neuroblasts were PSANCAM(+); however, neuroblasts also expressed doublecortin and functional voltage-dependent Ca(2+) channels. Neuroblasts and precursors had distinct outwardly rectifying K(+) current densities and passive membrane properties, particularly in precursors contacting each other, because of the contribution of gap junction coupling. Confirming the hypothesis that most are TAPs, cell tracing in brain slices revealed that within 2 days the majority of EGFR(+) cells had exited the cell cycle and differentiated into a progenitor displaying intermediate antigenic and functional properties between TAPs and neuroblasts. Thus, distinct functional and antigenic properties mark stem cell lineage progression in the neonatal SVZ. PMID:19489104

Cesetti, Tiziana; Obernier, Kirsten; Bengtson, C Peter; Fila, Tatiana; Mandl, Claudia; Hölzl-Wenig, Gabriele; Wörner, Kerstin; Eckstein, Volker; Ciccolini, Francesca

2009-06-01

148

A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: evidence for their Gondwanan affinities  

Microsoft Academic Search

It has often been assumed that Australasian Cretaceous dinosaur faunas were for the most part endemic, but with some Laurasian affinities. In this regard, some Australasian dinosaurs have been considered Jurassic relicts, while others were thought to represent typical Laurasian forms or endemic taxa. Furthermore, it has been proposed that some dinosaurian lineages, namely oviraptorosaurians, dromaeosaurids, ornithomimosaurians and protoceratopsians, may

Federico L. Agnolin; Martín D. Ezcurra; Diego F. Pais; Steven W. Salisbury

2010-01-01

149

The origin and early evolution of dinosaurs.  

PubMed

The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis, and Panphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as "all descendants of the most recent common ancestor of birds and Triceratops". Recent cladistic analyses of early dinosaurs agree that Pisanosaurus mertii is a basal ornithischian; that Herrerasaurus ischigualastensis and Staurikosaurus pricei belong in a monophyletic Herrerasauridae; that herrerasaurids, Eoraptor lunensis, and Guaibasaurus candelariensis are saurischians; that Saurischia includes two main groups, Sauropodomorpha and Theropoda; and that Saturnalia tupiniquim is a basal member of the sauropodomorph lineage. On the contrary, several aspects of basal dinosaur phylogeny remain controversial, including the position of herrerasaurids, E. lunensis, and G. candelariensis as basal theropods or basal saurischians, and the affinity and/or validity of more fragmentary taxa such as Agnosphitys cromhallensis, Alwalkeria maleriensis, Chindesaurus bryansmalli, Saltopus elginensis, and Spondylosoma absconditum. The identification of dinosaur apomorphies is jeopardized by the incompleteness of skeletal remains attributed to most basal dinosauromorphs, the skulls and forelimbs of which are particularly poorly known. Nonetheless, Dinosauria can be diagnosed by a suite of derived traits, most of which are related to the anatomy of the pelvic girdle and limb. Some of these are connected to the acquisition of a fully erect bipedal gait, which has been traditionally suggested to represent a key adaptation that allowed, or even promoted, dinosaur radiation during Late Triassic times. Yet, contrary to the classical "competitive" models, dinosaurs did not gradually replace other terrestrial tetrapods over the Late Triassic. In fact, the radiation of the group comprises at least three landmark moments, separated by controversial (Carnian-Norian, Triassic-Jurassic) extinction events. These are mainly characterized by early diversification in Carnian times, a Norian increase in diversity and (especially) abundance, and the occupation of new niches from the Early Jurassic onwards. Dinosaurs arose from fully bipedal ancestors, the diet of which may have been carnivorous or omnivorous. Whereas the oldest dinosaurs were geographically restricted to south Pangea, including rare ornithischians and more abundant basal members of the saurischian lineage, the group achieved a nearly global distribution by the latest Triassic, especially with the radiation of saurischian groups such as "prosauropods" and coelophysoids. PMID:19895605

Langer, Max C; Ezcurra, Martin D; Bittencourt, Jonathas S; Novas, Fernando E

2010-02-01

150

On Dinosaur Growth  

NASA Astrophysics Data System (ADS)

Despite nearly two centuries of investigation, a comprehensive understanding of dinosaur biology has proven intractable. The recent development of means to study tissue-level growth, age these animals, and make growth curves has revolutionized our knowledge of dinosaur lives. From such data it is now understood that dinosaurs grew both disruptively and determinately; that they rarely if ever exceeded a century in age; that they became giants through accelerated growth and dwarfed through truncated development; that they were likely endothermic, sexually matured like crocodiles, and showed survivorship like populations of large mammals; and that basal birds retained dinosaurian physiology.

Erickson, Gregory M.

2014-05-01

151

Melanosome evolution indicates a key physiological shift within feathered dinosaurs.  

PubMed

Inference of colour patterning in extinct dinosaurs has been based on the relationship between the morphology of melanin-containing organelles (melanosomes) and colour in extant bird feathers. When this relationship evolved relative to the origin of feathers and other novel integumentary structures, such as hair and filamentous body covering in extinct archosaurs, has not been evaluated. Here we sample melanosomes from the integument of 181 extant amniote taxa and 13 lizard, turtle, dinosaur and pterosaur fossils from the Upper-Jurassic and Lower-Cretaceous of China. We find that in the lineage leading to birds, the observed increase in the diversity of melanosome morphologies appears abruptly, near the origin of pinnate feathers in maniraptoran dinosaurs. Similarly, mammals show an increased diversity of melanosome form compared to all ectothermic amniotes. In these two clades, mammals and maniraptoran dinosaurs including birds, melanosome form and colour are linked and colour reconstruction may be possible. By contrast, melanosomes in lizard, turtle and crocodilian skin, as well as the archosaurian filamentous body coverings (dinosaur 'protofeathers' and pterosaur 'pycnofibres'), show a limited diversity of form that is uncorrelated with colour in extant taxa. These patterns may be explained by convergent changes in the key melanocortin system of mammals and birds, which is known to affect pleiotropically both melanin-based colouration and energetic processes such as metabolic rate in vertebrates, and may therefore support a significant physiological shift in maniraptoran dinosaurs. PMID:24522537

Li, Quanguo; Clarke, Julia A; Gao, Ke-Qin; Zhou, Chang-Fu; Meng, Qingjin; Li, Daliang; D'Alba, Liliana; Shawkey, Matthew D

2014-03-20

152

Dinosaur Count and Sort  

NSDL National Science Digital Library

In this activity, learners sort and count different colored plastic dinosaurs by various attributes including tail length, whether or not the dinosaurs have horns, etc. Learners discuss the basis of their sorting, describe individual dinosaurs as well as groups and count the whole as well as subsets of the whole. This identification, sorting and grouping based on different traits (physical attributes, diet, habitat) provides a strong foundation for the development of the concept of species. The lesson plan also explains that dinosaurs lived a long time ago, but because they are no longer alive today, they are said to be extinct. Reasons for their extinction and the concept of endangered species can be explored.

Omsi

2004-01-01

153

Two Kinds of Dinosaurs  

NSDL National Science Digital Library

This lesson introduces elementary students to the concept of soring living things into groups according to certain features. Students look at two kinds of dinosaurs based upon the structure of the pelvis and categorize them accordingly.

Wixom, Jo

154

DNA Methylation Restricts Lineage-specific Functions of Transcription Factor Gata4 during Embryonic Stem Cell Differentiation  

PubMed Central

DNA methylation changes dynamically during development and is essential for embryogenesis in mammals. However, how DNA methylation affects developmental gene expression and cell differentiation remains elusive. During embryogenesis, many key transcription factors are used repeatedly, triggering different outcomes depending on the cell type and developmental stage. Here, we report that DNA methylation modulates transcription-factor output in the context of cell differentiation. Using a drug-inducible Gata4 system and a mouse embryonic stem (ES) cell model of mesoderm differentiation, we examined the cellular response to Gata4 in ES and mesoderm cells. The activation of Gata4 in ES cells is known to drive their differentiation to endoderm. We show that the differentiation of wild-type ES cells into mesoderm blocks their Gata4-induced endoderm differentiation, while mesoderm cells derived from ES cells that are deficient in the DNA methyltransferases Dnmt3a and Dnmt3b can retain their response to Gata4, allowing lineage conversion from mesoderm cells to endoderm. Transcriptome analysis of the cells' response to Gata4 over time revealed groups of endoderm and mesoderm developmental genes whose expression was induced by Gata4 only when DNA methylation was lost, suggesting that DNA methylation restricts the ability of these genes to respond to Gata4, rather than controlling their transcription per se. Gata4-binding-site profiles and DNA methylation analyses suggested that DNA methylation modulates the Gata4 response through diverse mechanisms. Our data indicate that epigenetic regulation by DNA methylation functions as a heritable safeguard to prevent transcription factors from activating inappropriate downstream genes, thereby contributing to the restriction of the differentiation potential of somatic cells. PMID:23825962

Jakt, Lars Martin; Matsuoka, Chisa; Yamagiwa, Akiko; Niwa, Hitoshi; Okano, Masaki

2013-01-01

155

Redundant miR-3077-5p and miR-705 mediate the shift of mesenchymal stem cell lineage commitment to adipocyte in osteoporosis bone marrow  

PubMed Central

During the process of aging, especially for postmenopausal females, the cell lineage commitment of mesenchymal stem cells (MSCs) shift to adipocyte in bone marrow, resulting in osteoporosis. However, the cell-intrinsic mechanism of this cell lineage commitment switch is poorly understood. As the post-transcription regulation by microRNAs (miRNAs) has a critical role in MSCs differentiation and bone homeostasis, we performed comprehensive miRNAs profiling and found miR-705 and miR-3077-5p were significantly enhanced in MSCs from osteoporosis bone marrow. Both miR-705 and miR-3077-5p acted as inhibitors of MSCs osteoblast differentiation and promoters of adipocyte differentiation, by targeting on the 3?untranslated region (3?UTR) of HOXA10 and RUNX2 mRNA separately. Combined inhibition of miR-705 and miR-3077-5p rescued the cell lineage commitment disorder of MSCs through restoring HOXA10 and RUNX2 protein level. Furthermore, we found excessive TNF? and reactive oxygen species caused by estrogen deficiency led to the upregulation of both miRNAs through NF-?B pathway. In conclusion, our findings showed that redundant miR-705 and miR-3077-5p synergistically mediated the shift of MSCs cell lineage commitment to adipocyte in osteoporosis bone marrow, providing new insight into the etiology of osteoporosis at the post-transcriptional level. Moreover, the rescue of MSCs lineage commitment disorder by regulating miRNAs expression suggested a novel potential therapeutic target for osteoporosis as well as stem cell-mediated regenerative medicine. PMID:23598412

Liao, L; Yang, X; Su, X; Hu, C; Zhu, X; Yang, N; Chen, X; Shi, S; Shi, S; Jin, Y

2013-01-01

156

How Big Were Dinosaurs?  

NSDL National Science Digital Library

In this classroom activity, young students compare their feet to the foot of a large Apatosaur. The activity opens with background information for teachers about the enormous size range of dinosaurs. After using personal references to describe the size of dinosaurs, students examine the outline of an Apatosaur footprint. Students then estimate how many of their footprints would fit inside the Apatosaur footprint and conduct an experiment to test their estimate.

157

Dinosaur Trace Fossils  

NSDL National Science Digital Library

Anthony J. Martin, Senior Lecturer at Emory University, provides this interesting Website on dinosaur trace fossils -- namely tracks, trails, burrows, borings, gnawings, eggs, nests, gizzard stones, and dung of dinosaurs. The site offers a brief overview followed by illustrated descriptions of particular trace fossil types: Tracks and Trackways, Eggs and Nests, Tooth Marks, Gastroliths, and Coprolites. A series of links points users to further information, and a bibliography on Vertebrate Ichnology provides additional readings (through 1997).

Martin, Anthony J.

158

Rise of dinosaurs reveals major body-size transitions are driven by passive processes of trait evolution  

PubMed Central

A major macroevolutionary question concerns how long-term patterns of body-size evolution are underpinned by smaller scale processes along lineages. One outstanding long-term transition is the replacement of basal therapsids (stem-group mammals) by archosauromorphs, including dinosaurs, as the dominant large-bodied terrestrial fauna during the Triassic (approx. 252–201 million years ago). This landmark event preceded more than 150 million years of archosauromorph dominance. We analyse a new body-size dataset of more than 400 therapsid and archosauromorph species spanning the Late Permian–Middle Jurassic. Maximum-likelihood analyses indicate that Cope's rule (an active within-lineage trend of body-size increase) is extremely rare, despite conspicuous patterns of body-size turnover, and contrary to proposals that Cope's rule is central to vertebrate evolution. Instead, passive processes predominate in taxonomically and ecomorphologically more inclusive clades, with stasis common in less inclusive clades. Body-size limits are clade-dependent, suggesting intrinsic, biological factors are more important than the external environment. This clade-dependence is exemplified by maximum size of Middle–early Late Triassic archosauromorph predators exceeding that of contemporary herbivores, breaking a widely-accepted ‘rule’ that herbivore maximum size greatly exceeds carnivore maximum size. Archosauromorph and dinosaur dominance occurred via opportunistic replacement of therapsids following extinction, but were facilitated by higher archosauromorph growth rates. PMID:22298850

Sookias, Roland B.; Butler, Richard J.; Benson, Roger B. J.

2012-01-01

159

Fossilized Fashion: How Dinosaurs Looked  

NSDL National Science Digital Library

This activity is a printable one-page PDF handout, which focuses on dinosaur features. It includes an album of animal fashions in which students compare three dinosaur's frills with similar features found on animals alive today in order to determine their function and a "design your own dinosaur" challenge in which students create a dinosaur that has the features they'd like to see.

160

How Big Were the Dinosaurs?  

NSDL National Science Digital Library

In this activity (located on page 4 of PDF), learners gain insight into the actual size of dinosaurs and practice making estimations and measurements. Learners measure the lengths of various dinosaurs by measuring lengths of string in field or gym. Learners also estimate and measure these lengths by lying head to foot. Learners also compare and contrast the sizes of different dinosaur species.

Museum, Chicago C.

2011-01-01

161

A Dual Role for SOX10 in the Maintenance of the Postnatal Melanocyte Lineage and the Differentiation of Melanocyte Stem Cell Progenitors  

PubMed Central

During embryogenesis, the transcription factor, Sox10, drives the survival and differentiation of the melanocyte lineage. However, the role that Sox10 plays in postnatal melanocytes is not established. We show in vivo that melanocyte stem cells (McSCs) and more differentiated melanocytes express SOX10 but that McSCs remain undifferentiated. Sox10 knockout (Sox10fl; Tg(Tyr::CreER)) results in loss of both McSCs and differentiated melanocytes, while overexpression of Sox10 (Tg(DctSox10)) causes premature differentiation and loss of McSCs, leading to hair graying. This suggests that levels of SOX10 are key to normal McSC function and Sox10 must be downregulated for McSC establishment and maintenance. We examined whether the mechanism of Tg(DctSox10) hair graying is through increased expression of Mitf, a target of SOX10, by asking if haploinsufficiency for Mitf (Mitfvga9) can rescue hair graying in Tg(DctSox10) animals. Surprisingly, Mitfvga9 does not mitigate but exacerbates Tg(DctSox10) hair graying suggesting that MITF participates in the negative regulation of Sox10 in McSCs. These observations demonstrate that while SOX10 is necessary to maintain the postnatal melanocyte lineage it is simultaneously prevented from driving differentiation in the McSCs. This data illustrates how tissue-specific stem cells can arise from lineage-specified precursors through the regulation of the very transcription factors important in defining that lineage. PMID:23935512

Harris, Melissa L.; Buac, Kristina; Shakhova, Olga; Hakami, Ramin M.; Wegner, Michael; Sommer, Lukas; Pavan, William J.

2013-01-01

162

Shape of Mesozoic dinosaur richness  

NASA Astrophysics Data System (ADS)

The richness of Mesozoic Dinosauria is examined through the use of a new global database. Mesozoic dinosaurs show a steadily increasing rate of diversification, in part attributable to the development of new innovations driving an increasing variety of behavioral strategies. The data do not suggest that dinosaurs were decreasing in richness leading to extinction during the last ˜10 m.y. of the Cretaceous. Refinement of the dating of dinosaur fossils, rather than the collection of more dinosaurs, is the best way to resolve globally the rate of the Cretaceous-Tertiary dinosaur extinction.

Fastovsky, David E.; Huang, Yifan; Hsu, Jason; Martin-McNaughton, Jamie; Sheehan, Peter M.; Weishampel, David B.

2004-10-01

163

Dinosaur Eggs and Babies  

NASA Astrophysics Data System (ADS)

In the last couple of decades the study of dinosaur eggs and babies has proved to be one of the most exciting and profitable areas of dinosaur research. This is the first book solely devoted to this topic and reviews, in scientific detail, our present state of knowledge about this exciting area of palaeontology. Chapters in the book discuss all aspects of the science including the occurrence of eggs, nests and baby skeletons, descriptive osteology of juvenile skeletons, comparative histology of juvenile bone, analyses of eggs and egg shells, palaeoenvironments of nesting sites, nesting behaviour and developmental growth of baby dinosaurs. The volume will be an invaluable addition to the book collections of vertebrate palaeontologists and their graduate students.

Carpenter, Kenneth; Hirsch, Karl F.; Horner, John R.

1996-01-01

164

Dinosaurs in Argentina  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on recent dinosaur excavations in Argentina and why this is a good place to look for dinosaur fossils. Students read articles, conduct research, and complete worksheets to find out information about what is found in Argentina and why. Included are objectives, materials, procedures, discussion questions, evaluation ideas, performing extensions, suggested readings, and vocabulary. There are videos available to order which compliment this lesson, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

165

Dinosaur National Monument  

NSDL National Science Digital Library

This is the homepage of Dinosaur National Monument. Visitors can access information on the famous Douglas Quarry and visitor center, which preserves the fossils of dozens of dinosaurs from the Jurassic Period, including the Jurassic predator Allosaurus. There is also information on the Monument's plant and animal life, geology, and history and culture, including ancient rock art of the Fremont people. For teachers, there is information on planning field trips, either self-guided or with the assistance of a ranger. There is also a gallery of photos and multimedia resources.

Whitman, David; Hays, David

166

F-box Protein FBXL16 Binds PP2A-B55? and Regulates Differentiation of Embryonic Stem Cells along the FLK1+ Lineage*  

PubMed Central

The programmed formation of specific tissues from embryonic stem cells is a major goal of regenerative medicine. To identify points of intervention in cardiac tissue formation, we performed an siRNA screen in murine embryonic stem cells to identify ubiquitin system genes that repress cardiovascular tissue formation. Our screen uncovered an F-box protein, Fbxl16, as a repressor of one of the earliest steps in the cardiogenic lineage: FLK1+ progenitor formation. Whereas F-box proteins typically form SCF ubiquitin ligases, shotgun mass spectrometry revealed that FBXL16 instead binds protein phosphatase 2A (PP2A) containing a B55 specificity subunit (PP2AB55). Phosphoproteomic analyses indicate that FBXL16 negatively regulates phosphorylation of the established PP2AB55 substrate, vimentin. We suggest that FBXL16 negatively regulates the activity of B55?-PP2A to modulate the genesis of FLK1+ progenitor cells. PMID:24390425

Honarpour, Narimon; Rose, Christopher M.; Brumbaugh, Justin; Anderson, Jody; Graham, Robert L. J.; Sweredoski, Michael J.; Hess, Sonja; Coon, Joshua J.; Deshaies, Raymond J.

2014-01-01

167

Mll2 Controls Cardiac Lineage Differentiation of Mouse Embryonic Stem Cells by Promoting H3K4me3 Deposition at Cardiac-Specific Genes.  

PubMed

Trithorax group (TrxG) proteins play critical roles in transcriptional activation by promoting methylation of histone H3 Lysine 4 (H3K4), but the precise functions of the individual TrxG members during embryonic differentiation are not fully understood. Here we show that Mll2, a TrxG member, is required for proliferation but is dispensable for maintaining the pluripotency of mouse embryonic stem cells (ESCs). In addition, differentiation of ESCs toward mesodermal and endodermal lineages is severely altered and, in particular, the cardiac lineage differentiation of ESCs is completely abolished in the absence of Mll2. Moreover, the expression of core cardiac transcription factors and the levels of H3K4 tri-methylation of these cardiac-specific promoters are significantly decreased by the loss of Mll2. Taken together, our results reveal a critical role for Mll2 in proliferation and cardiac lineage differentiation of mouse ESCs, and provide novel molecular insight into the mechanisms of cardiac development and disease. PMID:24913280

Wan, Xiaoling; Liu, Lulu; Ding, Xiaodan; Zhou, Peipei; Yuan, Xiujie; Zhou, Zhongwen; Hu, Ping; Zhou, Hong; Li, Qiang; Zhang, Shenghai; Xiong, Sidong; Zhang, Yan

2014-10-01

168

The Production and Characteristics of a Mouse's Embryonic Stem Cell Lineage, Transfected by the Glia Neurotrophic Factor and Gene Fused with the Green Fluorescent Protein Gene  

PubMed Central

The influence that the expression of the human (glial-derived neurotrophic factor (GDNF)) neurotrophic factor has on the morphology and proliferative activity of embryonic stem cells (SC) of a mouse with R1 lineage, as well as their ability to form embroid bodies (EB), has been studied. Before that, using a PCR (polymerase chain reaction) coupled with reverse transcription, it was shown that, in this very lineage of the embryonic SC, the expression of the receptors' genes is being fulfilled for the neurotropfic RET and GFR?1 glia factor. The mouse's embryonic SC lineage has been obtained, transfected by the human GDNF gene, and has been fused with the "green" fluorescent protein (GFP) gene. The presence of the expression of the human GDNF gene in the cells was shown by northern hybridization and the synthesis of its albuminous product by immunocitochemical coloration with the use of specific antibodies. The reliable slowing-down of the embriod-body formation by the embryonic SC transfected by the GDNF gene has been shown. No significant influence of the expression of the GDNF gene on the morphology and the proliferative activity of the transfected embryonic SCs has been found when compared with the control ones. PMID:22649595

Arsenieva, E. L.; Kuzmin, I. V.; Manuilova, E. S.; Novosadova, E. V.; Murkin, E. V.; Pavlova, G. V.; Tarantul, V. Z.

2009-01-01

169

Combined use of platelet rich plasma and vitamin C positively affects differentiation in vitro to mesodermal lineage of adult adipose equine mesenchymal stem cells.  

PubMed

Repair of injured soft and hard tissues in horses can benefit greatly from the use of regenerative therapies with mesenchymal stem cells (MSC). Vitamin-C and platelet-rich-plasma had been used for in vitro differentiation of MSC. This study was aimed to evaluate the effect of vitamin-C, platelet-rich-plasma and their combination on the in vitro differentiation of adipose horse MSC. We isolated MSC from horse fat and differentiated them in vitro into osteogenic and chondrogenic lineages, as demonstrated by specific staining and RT-qPCR of selected genes. Combining vitamin-C and plasma-rich-platelet positively affected the ability of MSC to differentiate in vitro into mesodermal lineages during 14 days of culture; this effect was not as marked when differentiation was attempted for 21 days. This provides valuable information on the effect of combined use of these molecules in regenerative therapies and their potential application along stem cells for lesions of musculoskeletal tissue in sport horses. PMID:24377415

Castro, F O; Torres, A; Cabezas, J; Rodríguez-Alvarez, Ll

2014-02-01

170

Aberrant intestinal stem cell lineage dynamics in Peutz-Jeghers syndrome and familial adenomatous polyposis consistent with protracted clonal evolution in the crypt  

PubMed Central

Objective Genetic predisposition to cancer in Peutz–Jeghers syndrome (PJS) and the role of germline serine–threonine kinase (LKB1) mutations are poorly understood. The authors studied the effect of germline LKB1 mutations on intestinal stem cell dynamics in unaffected flat PJS mucosa. Recent research has documented that the intestinal crypt houses multiple equipotent stem cell lineages. Lineages continuously compete through random drifts, while somatically inherited methylation patterns record clonal diversity. Design To study the effect of germline LKB1 mutations on clonal expansion, the authors performed quantitative analyses of cardiac-specific homeobox methylation pattern diversity in crypts isolated from unaffected colonic mucosa obtained from archival PJS patient material. The authors compared methylation density and methylation pattern diversity in patients with PJS to those in patients with familial adenomatous polyposis and age-matched controls. Results The percentage of total methylation is comparable between groups, but the number of unique methylation patterns is significantly increased for patients with familial adenomatous polyposis and patients with PJS compared to control subjects. Conclusions Monoallelic LKB1 loss is not silent and provokes a protracted clonal evolution in the crypt. The increased methylation pattern diversity observed in unaffected PJS mucosa predicts that premalignant lesions will arise at an accelerated pace compared to the general population. PMID:21940722

Langeveld, Danielle; Jansen, Marnix; de Boer, D V; van Sprundel, Mariska; Brosens, Lodewijk A A; Morsink, Folkert H; Giardiello, Francis M; Offerhaus, G Johan A; de Leng, Wendy W J

2013-01-01

171

Differentiation of retinal ganglion cells and photoreceptor precursors from mouse induced pluripotent stem cells carrying an atoh7/math5 lineage reporter.  

PubMed

The neural retina is a critical component of the visual system, which provides the majority of sensory input in humans. Various retinal degenerative diseases can result in the permanent loss of retinal neurons, especially the light-sensing photoreceptors and the centrally projecting retinal ganglion cells (RGCs). The replenishment of lost RGCs and the repair of optic nerve damage are particularly challenging, as both RGC specification and their subsequent axonal growth and projection involve complex and precise regulation. To explore the developmental potential of pluripotent stem cell-derived neural progenitors, we have established mouse iPS cells that allow cell lineage tracing of progenitors that have expressed Atoh7/Math5, a bHLH transcription factor required for RGC production. These Atoh7 lineage reporter iPS cells encode Cre to replace one copy of the endogenous Atoh7 gene and a Cre-dependent YFP reporter in the ROSA locus. In addition, they express pluripotent markers and are capable of generating teratomas in vivo. Under anterior neural induction and neurogenic conditions in vitro, the Atoh7-Cre/ROSA-YFP iPS cells differentiate into neurons that co-express various RGC markers and YFP, indicating that these neurons are derived from Atoh7-expressing progenitors. Consistent with previous in vivo cell lineage studies, the Atoh7-Cre/ROSA-YFP iPS cells also give rise to a subset of Crx-positive photoreceptor precursors. Furthermore, inhibition of Notch signaling in the iPSC cultures results in a significant increase of YFP-positive RGCs and photoreceptor precursors. Together, these results show that Atoh7-Cre/ROSA-YFP iPS cells can be used to monitor the development and survival of RGCs and photoreceptors from pluripotent stem cells. PMID:25401462

Xie, Bin-Bin; Zhang, Xiang-Mei; Hashimoto, Takao; Tien, Amy H; Chen, Andrew; Ge, Jian; Yang, Xian-Jie

2014-01-01

172

Differentiation of Retinal Ganglion Cells and Photoreceptor Precursors from Mouse Induced Pluripotent Stem Cells Carrying an Atoh7/Math5 Lineage Reporter  

PubMed Central

The neural retina is a critical component of the visual system, which provides the majority of sensory input in humans. Various retinal degenerative diseases can result in the permanent loss of retinal neurons, especially the light-sensing photoreceptors and the centrally projecting retinal ganglion cells (RGCs). The replenishment of lost RGCs and the repair of optic nerve damage are particularly challenging, as both RGC specification and their subsequent axonal growth and projection involve complex and precise regulation. To explore the developmental potential of pluripotent stem cell-derived neural progenitors, we have established mouse iPS cells that allow cell lineage tracing of progenitors that have expressed Atoh7/Math5, a bHLH transcription factor required for RGC production. These Atoh7 lineage reporter iPS cells encode Cre to replace one copy of the endogenous Atoh7 gene and a Cre-dependent YFP reporter in the ROSA locus. In addition, they express pluripotent markers and are capable of generating teratomas in vivo. Under anterior neural induction and neurogenic conditions in vitro, the Atoh7-Cre/ROSA-YFP iPS cells differentiate into neurons that co-express various RGC markers and YFP, indicating that these neurons are derived from Atoh7-expressing progenitors. Consistent with previous in vivo cell lineage studies, the Atoh7-Cre/ROSA-YFP iPS cells also give rise to a subset of Crx-positive photoreceptor precursors. Furthermore, inhibition of Notch signaling in the iPSC cultures results in a significant increase of YFP-positive RGCs and photoreceptor precursors. Together, these results show that Atoh7-Cre/ROSA-YFP iPS cells can be used to monitor the development and survival of RGCs and photoreceptors from pluripotent stem cells. PMID:25401462

Hashimoto, Takao; Tien, Amy H.; Chen, Andrew; Ge, Jian; Yang, Xian-Jie

2014-01-01

173

Relative Speed of Dinosaurs  

NSDL National Science Digital Library

In this activity, learners interpret three trackways and use measurements and a formula to infer the relative speed of dinosaurs. A portion of the activity details how students can create their own trackways and evaluate the accuracy of the formula. This step-by-step lesson plan includes an illustrated look at stride length and a reproducible worksheet for learners to complete.

History, American M.

2007-01-01

174

Dinosaurs of Portugal  

Microsoft Academic Search

A synthesis on the state of art on dinosaur knowledge in Portugal is presented. The following genera have been recognized: Ceratosaurus, Torvosaurus, Lourinhanosaurus, Allosaurus, cf. Compsognathus, Stokesosaurus, cf. Richardoestesia, cf. Archaeopteryx, Euronychodon, cf. Paronychodon, Dinheirosaurus, Lourinhasaurus, Lusotitan, cf. Pleurocoelus, Lusitanosaurus, Dacentrurus, Dracopelta, Phyllodon, Hypsilophodon, Alocodon, Trimucrodon, Draconyx, Iguanodon, and Taveirosaurus. Most are from Late Jurassic localities at the Lourinhã area

Miguel Telles Antunes; Octávio Mateus

2003-01-01

175

Riding the Dinosaur Wave.  

ERIC Educational Resources Information Center

As his geology students' specialized knowledge of the Mesozoic era increased, a high school teacher realized he needed a way to showcase their work. The Mesozoic Resource Center's biggest hit was a walk-through diorama showing how life might have been during each of three Mesozoic periods. Highlights included two gigantic student-built dinosaur

Girod, Mark

1998-01-01

176

When the Dinosaurs Lived.  

ERIC Educational Resources Information Center

Background information and ready-to-copy student materials are provided for activities that examine the history of the earth and focus on what life was like during the age of dinosaurs. Each activity includes an objective, list of materials needed, recommended age level(s), subject area(s), and instructional strategies. (JN)

NatureScope, 1985

1985-01-01

177

Dinosaurs: Bigger Than You Think  

NSDL National Science Digital Library

In this classroom activity, middle school students examine the wide-ranging sizes of dinosaurs. The activity opens with background information about the enormous range of dinosaur sizes and a classroom discussion in which students describe the size of some of the dinosaurs they know. Then, working from gridded drawings which are provided, students create either a life-size drawing of a Tyrannosaurus rex head or a life-size drawing of a complete Protoceratops.

178

Co-Culture of Hematopoietic Stem/Progenitor Cells with Human Osteblasts Favours Mono/Macrophage Differentiation at the Expense of the Erythroid Lineage  

PubMed Central

Hematopoietic stem cells (HSCs) are located in the bone marrow in a specific microenvironment referred as the hematopoietic stem cell niche, where HSCs interact with a variety of stromal cells. Though several components of the stem cell niche have been identified, the regulatory mechanisms through which such components regulate the stem cell fate are still unknown. In order to address this issue, we investigated how osteoblasts (OBs) can affect the molecular and functional phenotype of Hematopoietic Stem/Progenitor Cells (HSPCs) and vice versa. For this purpose, human CD34+ cells were cultured in direct contact with primary human OBs. Our data showed that CD34+ cells cultured with OBs give rise to higher total cell numbers, produce more CFUs and maintain a higher percentage of CD34+CD38- cells compared to control culture. Moreover, clonogenic assay and long-term culture results showed that co-culture with OBs induces a strong increase in mono/macrophage precursors coupled to a decrease in the erythroid ones. Finally, gene expression profiling (GEP) allowed us to study which signalling pathways were activated in the hematopoietic cell fraction and in the stromal cell compartment after coculture. Such analysis allowed us to identify several cytokine-receptor networks, such as WNT pathway, and transcription factors, as TWIST1 and FOXC1, that could be activated by co-culture with OBs and could be responsible for the biological effects reported above. Altogether our results indicate that OBs are able to affect HPSCs on 2 different levels: on one side, they increase the immature progenitor pool in vitro, on the other side, they favor the expansion of the mono/macrophage precursors at the expense of the erythroid lineage. PMID:23349713

Salati, Simona; Lisignoli, Gina; Manferdini, Cristina; Pennucci, Valentina; Zini, Roberta; Bianchi, Elisa; Norfo, Ruggiero; Facchini, Andrea; Ferrari, Sergio; Manfredini, Rossella

2013-01-01

179

Cell Lineage and Regional Identity of Cultured Spinal Cord Neural Stem Cells and Comparison to Brain-Derived Neural Stem Cells  

Microsoft Academic Search

Neural stem cells (NSCs) can be isolated from different regions of the central nervous system. There has been controversy whether regional differences amongst stem and progenitor cells are cell intrinsic and whether these differences are maintained during expansion in culture. The identification of inherent regional differences has important implications for the use of these cells in neural repair. Here, we

Theresa K. Kelly; Stanislav L. Karsten; Daniel H. Geschwind; Harley I. Kornblum; Daphne Soares

2009-01-01

180

Weigh a Dinosaur  

NSDL National Science Digital Library

Students select dinosaurian models (toys) from a selection of Carnegie, Natural History Museum (London) and other manufacturers (Schleich, Safari, etc). Each student identifies their dinosaur, places it on a cladogram (provided) and determines when it lived. They then measure the dinosaur in three dimensions (length, width, height), compare one or more of these dimensions to "real" dimensions provided (usually the model says what the length was). Dividing "real" by "measured" yields a scale. Students then determine how much water their model displaces. NOTE: Most textbooks show this happening with a beaker. Beakers are no where near accurate enough to use, and many dinosaurs dont fit in them anyway. You need either extremely large graduated cylinders (unlikely) or else large containers in a sink. What works best is to have students fill a container to overflowing (in the sink, obviously), then gently dunk their dinosaur, causing the vessel to overflow, then retrieve their dinosaur. THEN you can use a graduated cylinder to refill the container and measure the amount of water displaced. Once students have a scale and a volume, the can cube the former and multiply it by the latter to yield an estimate of the volume of the actual dinosaur. Multiplying this by a density estimate provides an estimated mass. I have them bracket it by taking 0.9kg/L and 1.05kg/L for "light" and "heavy." Feathered theropods are even lighterâI have them use 0.8 g/L for the light estimate. They then record their result (I am trying to generate a spreadsheet of these measurements over the years) and compare it to a published estimate. I should probably base their grade on the ratio of their estimate to the "actual" (if light, reversed if heavy) but generally just try to "police" the workâif they are way off, they need to go back and find what arithmetic error led to the problem. In the introductory classes this is a simple 1-sheet worksheet (front and back). For the honors students, they take the assignment home and write it up. PS. I let the anthropology majors play with models of Pleistocene megafauna instead.

Heckert, Andrew

181

Differentiation of Human Umbilical Cord Matrix Mesenchymal Stem Cells into Neural-Like Progenitor Cells and Maturation into an Oligodendroglial-Like Lineage  

PubMed Central

Mesenchymal stem cells (MSCs) are viewed as safe, readily available and promising adult stem cells, which are currently used in several clinical trials. Additionally, their soluble-factor secretion and multi-lineage differentiation capacities place MSCs in the forefront of stem cell types with expected near-future clinical applications. In the present work MSCs were isolated from the umbilical cord matrix (Wharton's jelly) of human umbilical cord samples. The cells were thoroughly characterized and confirmed as bona-fide MSCs, presenting in vitro low generation time, high proliferative and colony-forming unit-fibroblast (CFU-F) capacity, typical MSC immunophenotype and osteogenic, chondrogenic and adipogenic differentiation capacity. The cells were additionally subjected to an oligodendroglial-oriented step-wise differentiation protocol in order to test their neural- and oligodendroglial-like differentiation capacity. The results confirmed the neural-like plasticity of MSCs, and suggested that the cells presented an oligodendroglial-like phenotype throughout the differentiation protocol, in several aspects sharing characteristics common to those of bona-fide oligodendrocyte precursor cells and differentiated oligodendrocytes. PMID:25357129

Leite, Cristiana; Silva, N. Tatiana; Mendes, Sandrine; Ribeiro, Andreia; de Faria, Joana Paes; Lourenco, Tania; dos Santos, Francisco; Andrade, Pedro Z.; Cardoso, Carla M. P.; Vieira, Margarida; Paiva, Artur; da Silva, Claudia L.; Cabral, Joaquim M. S.; Relvas, Joao B.; Graos, Mario

2014-01-01

182

Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs  

PubMed Central

Background One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved in the lineage leading to birds. Although it is well established that high, sustained growth rates and, presumably, high activity levels are ancestral for dinosaurs and pterosaurs (clade Ornithodira), other independent lines of evidence for high metabolic rates, locomotor costs, or endothermy are needed. For example, some studies have suggested that, because large dinosaurs may have been homeothermic due to their size alone and could have had heat loss problems, ectothermy would be a more plausible metabolic strategy for such animals. Methodology/Principal Findings Here we describe two new biomechanical approaches for reconstructing the metabolic rate of 14 extinct bipedal dinosauriforms during walking and running. These methods, well validated for extant animals, indicate that during walking and slow running the metabolic rate of at least the larger extinct dinosaurs exceeded the maximum aerobic capabilities of modern ectotherms, falling instead within the range of modern birds and mammals. Estimated metabolic rates for smaller dinosaurs are more ambiguous, but generally approach or exceed the ectotherm boundary. Conclusions/Significance Our results support the hypothesis that endothermy was widespread in at least larger non-avian dinosaurs. It was plausibly ancestral for all dinosauriforms (perhaps Ornithodira), but this is perhaps more strongly indicated by high growth rates than by locomotor costs. The polarity of the evolution of endothermy indicates that rapid growth, insulation, erect postures, and perhaps aerobic power predated advanced “avian” lung structure and high locomotor costs. PMID:19911059

Pontzer, Herman; Allen, Vivian; Hutchinson, John R.

2009-01-01

183

A Dinosaur's Neighborhood  

NSDL National Science Digital Library

This website is part of National Geographic's Xpeditions Hall, and offers videos, links to related sites, and other interactive features to help students understand the importance of environment as it relates to organisms and where they choose to live. This activity uses the dinosaur Tyrannosaurus rex as an example and prompts students to find out what kind of environment would best suit this creature's needs. These lesson plans were written by educators and have been tested in the classroom.

184

Dinosaur Bone Experiments  

NSDL National Science Digital Library

This activity features two connected hands-on activities about dinosaur bones. Using chicken or turkey bones and regular household items, learners explore the scientific process of studying fossilized bones. By exposing the bones to vinegar or heat, learners begin to understand how paleontologists use chemical processes to study the bones of animals long dead and gone. Use this bone-themed activity around the Thanksgiving holiday and repurpose some leftovers.

Science, Lawrence H.

2005-01-01

185

Using human plasma supplemented medium to cultivate human bone marrow-derived mesenchymal stem cell and evaluation of its multiple-lineage potential.  

PubMed

The objective of this study was to evaluate the proliferation and the multiple-lineage differentiation capacity when bone marrow mesenchymal stem cells (BMSCs) were cultured short-term in autologous serum/plasma instead of fetal calf serum (FCS). The BMSCs from 12 donors were cultivated individually in 10% autogenic plasma or serum, with or without bFGF and EGF growth factors. Cell proliferation was examined by a Tetrazolium assay (MTT) after passages 1, 3, and 5. A medium supplemented with 10% human plasma or serum was sufficient to propagate BMSCs. However, no significant proliferation was shown when bFGF and EGF (20 ng/mL each) were added into the medium with autologous serum/plasma. We examined, inductions of adipogenesis, osteogenesis, and chondrocytogenesis, as capacities of multiple-lineage differentiation of cultivated BMSCs (passages 8). Differentiation was investigated by both RT-PCR and immunohistochemistry staining (IHC). Qualitative evidence demonstrated the differentiation capacity was preserved in cultivated BMSCs with autologous serum/plasma. PMID:16387155

Lin, H-T; Tarng, Y-W; Chen, Y-C; Kao, C-L; Hsu, C-J; Shyr, Y-M; Ku, H-H; Chiou, S H

2005-12-01

186

Determination of osteogenic or adipogenic lineages in muscle-derived stem cells (MDSCs) by a collagen-binding peptide (CBP) derived from bone sialoprotein (BSP)  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer CBP sequence is identified from BSP and has collagen binding activity. Black-Right-Pointing-Pointer CBP directly activates the MAPK signaling, especially ERK1/2. Black-Right-Pointing-Pointer CBP increase osteoblastic differentiation by the activation of Runx2. Black-Right-Pointing-Pointer CBP decrease adipogenic differentiation by the inhibition of PPAR{gamma}. -- Abstract: Bone sialoprotein (BSP) is a mineralized, tissue-specific, non-collagenous protein that is normally expressed only in mineralized tissues such as bone, dentin, cementum, and calcified cartilage, and at sites of new mineral formation. The binding of BSP to collagen is thought to be important for initiating bone mineralization and bone cell adhesion to the mineralized matrix. Several recent studies have isolated stem cells from muscle tissue, but their functional properties are still unclear. In this study, we examined the effects of a synthetic collagen-binding peptide (CBP) on the differentiation efficiency of muscle-derived stem cells (MDSCs). The CBP sequence (NGVFKYRPRYYLYKHAYFYPHLKRFPVQ) corresponds to residues 35-62 of bone sialoprotein (BSP), which are located within the collagen-binding domain in BSP. Interestingly, this synthetic CBP inhibited adipogenic differentiation but increased osteogenic differentiation in MDSCs. The CBP also induced expression of osteoblastic marker proteins, including alkaline phosphatase (ALP), type I collagen, Runt-related transcription factor 2 (Runx2), and osteocalcin; prevented adipogenic differentiation in MDSCs; and down-regulated adipose-specific mRNAs, such as adipocyte protein 2 (aP2) and peroxisome proliferator-activated receptor {gamma}. The CBP increased Extracellular signal-regulated kinases (ERK) 1/2 protein phosphorylation, which is important in lineage determination. These observations suggest that this CBP determines the osteogenic or adipogenic lineage in MDSCs by activating ERK1/2. Taken together, a novel CBP could be a useful candidate for regenerating bone and treating osteoporosis, which result from an imbalance in osteogenesis and adipogenesis differentiation.

Choi, Yoon Jung [Dental Regenerative Biotechnology Major, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 110-749 (Korea, Republic of)] [Dental Regenerative Biotechnology Major, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 110-749 (Korea, Republic of); Lee, Jue Yeon [Research Institute, Nano Intelligent Biomedical Engineering Corporation (NIBEC), Seoul (Korea, Republic of)] [Research Institute, Nano Intelligent Biomedical Engineering Corporation (NIBEC), Seoul (Korea, Republic of); Lee, Seung Jin [Department of Industrial Pharmacy, College of Pharmacy, Ewha Womans University, Seoul (Korea, Republic of)] [Department of Industrial Pharmacy, College of Pharmacy, Ewha Womans University, Seoul (Korea, Republic of); Chung, Chong-Pyoung, E-mail: ccpperio@snu.ac.kr [Research Institute, Nano Intelligent Biomedical Engineering Corporation (NIBEC), Seoul (Korea, Republic of) [Research Institute, Nano Intelligent Biomedical Engineering Corporation (NIBEC), Seoul (Korea, Republic of); Department of Periodontology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul (Korea, Republic of); Park, Yoon Jeong, E-mail: parkyj@snu.ac.kr [Dental Regenerative Biotechnology Major, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 110-749 (Korea, Republic of); Research Institute, Nano Intelligent Biomedical Engineering Corporation (NIBEC), Seoul (Korea, Republic of)

2012-03-09

187

Gastroliths in An Ornithopod Dinosaur  

Microsoft Academic Search

Gastroliths (stomach stones) are known from many extant and extinct vertebrates, including dinosaurs. Reported here is the first unambiguous record of gastroliths in an ornitho? pod dinosaur. Clusters of small stones found in the abdomi? nal region of three articulated skeletons of Gasparinisaura cincosaltensis were identified as gastroliths on the basis of taphonomic and sedimentologic evidence. The large number of

Ignacio A. Cerda

2008-01-01

188

Making Sense of Dinosaur Tracks  

ERIC Educational Resources Information Center

What do paleontologists, dinosaur tracks, and the nature of science have in common? They're combined here in an inquiry activity where students use methods of observation and inference to devise evidence-based explanations for the data they collect about dinosaur tracks, much like the methods used by paleontologists. Students then debate the…

MacKenzie, Ann Haley; McDowell, Brian

2012-01-01

189

Fossils 1: Fossils and Dinosaurs  

NSDL National Science Digital Library

This lesson will go beyond naming dinosaurs and give students a broad understanding of how we know about the great beasts. This lesson focuses on what we have learned and can learn from fossils. The follow-up lesson, Dinosaurs Fossils - Uncovering the Facts, explores what information can be discerned by comparing fossils to living organisms.

Science Netlinks;

2001-10-20

190

The Extinction of the Dinosaurs  

Microsoft Academic Search

Dinosaur extinction is still a major enigma of Earth history. In this review article, extinctions in the geological record will be briefly mentioned. Many of the imaginative theories for the extinction of the dinosaurs will also be presented. Within the uniformitarian paradigm, the meteorite impact theory, once considered 'outrageous', now is the dominant theory. However, the volcanic theory is still

MICHAEL J. OARD

1997-01-01

191

Differentiation of pluripotent embryonic stem cells into the neuronal lineage in vitro gives rise to mature inhibitory and excitatory neurons  

Microsoft Academic Search

Embryonic stem (ES) cells represent a suitable model to analyze cell differentiation processes in vitro. Here, we report that pluripotent ES cells of the line BLC 6 differentiate in vitro into neuronal cells possessing the complex electrophysiological and immunocytochemical properties of postmitotic nerve cells. In the course of differentiation BLC 6-derived neurons differentially express voltagedependent (K+, Na+, Ca2+) and receptor-operated

Carsten Strübing; Gudrun Ahnert-Hilger; Jin Shan; Bertram Wiedenmann; Jürgen Hescheler; Anna M. Wobus

1995-01-01

192

Dinosaur Skull and Body Length Predictions  

NSDL National Science Digital Library

In this activity (located on page 2 of PDF), learners will look for a relationship between skull size and body length among various dinosaurs. Starting from a list of dinosaur measurements, learners will compare dinosaur sizes to common objects and create a chart that plots body length against skull length to see if the data predicts other dinosaurs' length from skull size. Relates to the linked video, DragonflyTV GPS: Baby Dinosaurs.

Twin Cities Public Television, Inc.

2007-01-01

193

The Wnt Receptor, Lrp5, Is Expressed by Mouse Mammary Stem Cells and Is Required to Maintain the Basal Lineage  

Microsoft Academic Search

BackgroundEctopic Wnt signaling induces increased stem\\/progenitor cell activity in the mouse mammary gland, followed by tumor development. The Wnt signaling receptors, Lrp5\\/6, are uniquely required for canonical Wnt activity. Previous data has shown that the absence of Lrp5 confers resistance to Wnt1-induced tumor development.Methodology\\/Principal FindingsHere, we show that all basal mammary cells express Lrp5, and co-express Lrp6 in a similar

Nisha M. Badders; Shruti Goel; Rod J. Clark; Kristine S. Klos; Soyoung Kim; Anna Bafico; Charlotta Lindvall; Bart O. Williams; Caroline M. Alexander; Joseph Najbauer

2009-01-01

194

What's New with Dinosaurs  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on a current controversary among scientists over whether dinosaurs were warm-blooded or cold-blooded. Students research both sides of the argument and then present a debate over this topic. It includes objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

195

When Dinosaurs Ruled  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on the Mesozoic Era, when dinosaurs roamed the Earth. Through research and activities students learn about the plants and animals that inhabited Earth at that time, and the changes in plant life that occurred due to the development of animal life. It includes objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

Demary, John

196

Induction of ram bone marrow mesenchymal stem cells into germ cell lineage using transforming growth factor-? superfamily growth factors.  

PubMed

Several studies have proposed that in vitro generation of germ cells (GCs) from stem cells can be considered a future option for infertility treatment. Mesenchymal stem cells (MSCs) have the capability to differentiate into male GCs with the use of inducers such as retinoic acid. Transforming growth factor-beta 1 (TGFb1) has been shown to play important roles in male fertility and spermatogenesis. Bone morphogenic protein 4 (BMP4) and BMP8b are also involved in the derivation of primordial GCs (PGCs) from epiblast cells. Therefore, this study aims to determine whether TGFb1, BMP4 and BMP8b can initiate transdifferentiation of MSCs into GCs in vitro and to determine the type of changes that occur in the expression of GC-specific markers. In this study, we have divided passage-3 ram bone marrow (BM)-MSCs into three main groups (BMP4, BMP8b and TGFb1) which were separately treated with 10 ng/ml TGFb1, 100 ng/ml BMP4 and 100 ng/ml BMP8b for a period of 21 days. We have evaluated the ability of these groups to differentiate into GCs by assessing expressions of GC-specific markers with reverse transcription PCR (RT-PCR), quantitative RT-PCR (qRT-PCR), immunocytochemistry, morphological changes and alkaline phosphatase (ALP) activity. Our results showed that BMP4 and BMP8b induced PGCs properties in some BM-MSCs and TGFb1 formed spermatogonial stem cells (SSCs) and spermatogonia-like cells in BM-MSCs culture. The important results of this study provide the basis for additional studies to determine the exact mechanism of GCs differentiation and possibly solve the problem of infertility. PMID:24888234

Ghasemzadeh-Hasankolaei, M; Sedighi-Gilani, M A; Eslaminejad, M B

2014-08-01

197

Transcriptome profiling and sequencing of differentiated human hematopoietic stem cells reveal lineage-specific expression and alternative splicing of genes  

PubMed Central

Hematopoietic differentiation is strictly regulated by complex network of transcription factors that are controlled by ligands binding to cell surface receptors. Disruptions of the intricate sequences of transcriptional activation and suppression of multiple genes cause hematological diseases, such as leukemias, myelodysplastic syndromes, or myeloproliferative syndromes. From a clinical standpoint, deciphering the pattern of gene expression during hematopoiesis may help unravel disease-specific mechanisms in hematopoietic malignancies. Herein, we describe a human in vitro hematopoietic model system where lineage-specific differentiation of CD34+ cells was accomplished using specific cytokines. Microarray and RNAseq-based whole transcriptome and exome analysis was performed on the differentiated erythropoietic, granulopoietic, and megakaryopoietic cells to delineate changes in expression of whole transcripts and exons. Analysis on the Human 1.0 ST exon arrays indicated differential expression of 172 genes (P < 0.0000001) and significant alternate splicing of 86 genes during differentiation. Pathway analysis identified these genes to be involved in Rac/RhoA signaling, Wnt/B-catenin signaling and alanine/aspartate metabolism. Comparison of the microarray data to next generation RNAseq analysis during erythroid differentiation demonstrated a high degree of correlation in gene (R = 0.72) and exon (R = 0.62) expression. Our data provide a molecular portrait of events that regulate differentiation of hematopoietic cells. Knowledge of molecular processes by which the cells acquire their cell-specific fate would be beneficial in developing cell-based therapies for human diseases. PMID:21828245

Liu, Poching; Barb, Jennifer; Woodhouse, Kimberly; Taylor, James G.; Munson, Peter J.

2011-01-01

198

Micro-/Nano- sized hydroxyapatite directs differentiation of rat bone marrow derived mesenchymal stem cells towards an osteoblast lineage  

NASA Astrophysics Data System (ADS)

Regenerative medicine consisting of cells and materials provides a new way for the repair and regeneration of tissues and organs. Nano-biomaterials are highlighted due to their advantageous features compared with conventional micro-materials. The aim of this study is to investigate the effects of micro-/nano- sized hydroxyapatite (?/n-HA) on the osteogenic differentiation of rat bone marrow derived mesenchymal stem cells (rBMSCs). ?/n-HA were prepared by a microwave synthesizer and precipitation method, respectively. Different sizes of ?/n-HA were characterized by IR, XRD, SEM, TEM and co-cultured with rBMSCs. It was shown that rBMSCs expressed higher levels of osteoblast-related markers by n-HA than ?-HA stimulation. The size of HA is an important factor for affecting the osteogenic differentiation of rBMSCs. This provides a new avenue for mechanistic studies of stem cell differentiation and a new approach to obtain more committed differentiated cells.

Huang, Yan; Zhou, Gang; Zheng, Lisha; Liu, Haifeng; Niu, Xufeng; Fan, Yubo

2012-03-01

199

GEOL 104 Dinosaurs: A Natural History Homework 3: Dinosaur Relationships  

E-print Network

. The [ left | right ] pelvis is from a saurischian. 26. The [ left | right ] pelvis is from an ornithischian-pointing pelvis associated with plant-eating? Sauropod dinosaurs evolved numerous approaches for feeding high

Holtz Jr., Thomas R.

200

Nanofiber-based polyethersulfone scaffold and efficient differentiation of human induced pluripotent stem cells into osteoblastic lineage.  

PubMed

Human induced pluripotent stem cells (iPSCs) have been shown to have promising potential for regenerative medicine and tissue engineering applications. In the present study, osteogenic differentiation of human iPSCs was evaluated on polyethersulfone (PES) nanofibrous scaffold. According to the results, higher significant expressions of common osteogenic-related genes such as runx2, collagen type I, osteocalcin and osteonectin was observed in PES seeded human iPSCs compared with control. Alizarin red staining and alkaline phosphatase activity of differentiated iPSCs demonstrated significant osteoblastic differentiation potential of these cells. In this study biocompatibility of PES nanofibrous scaffold confirmed by flattened and spreading morphology of iPSCs under osteoblastic differentiation inductive culture. Taking together, nanofiber-based PES scaffold seeded iPSCs showed the highest capacity for differentiation into osteoblasts-like cells. These cells and PES scaffold were demonstrated to have great efficiency for treatment of bone damages and lesions. PMID:23657591

Ardeshirylajimi, Abdolreza; Hosseinkhani, Saman; Parivar, Kazem; Yaghmaie, Parichehr; Soleimani, Masoud

2013-07-01

201

How Do Scientists Find Dinosaur Fossils?  

NSDL National Science Digital Library

This lesson plan is about the process by which paleontologists locate, excavate, and study dinosaurs. Students will write journal entries pretending they are on a dinosaur dig. They will also make fact sheets about this recently discovered Jobaria dinosaur; place Jobaria into a timeline to indicate the periods in which it lived; visit a website to learn about the steps involved in finding and excavating dinosaur fossils, then list these steps and explain their importance; describe what the bones in an interactive Jobaria skeleton indicate about this dinosaur; and view pictures of a trip teenagers took to look for dinosaur fossils.

202

Centering on Fossils and Dinosaurs.  

ERIC Educational Resources Information Center

Describes a set of 10 activities which introduce mainstreamed junior high school students to concepts relating to fossils and dinosaurs. Provides students with opportunities for learning the concepts of change and adaptation, as well as fossil facts and terminology. (TW)

Coble, Charles R.; McCall, Gregory K.

1986-01-01

203

The Extinction of the Dinosaurs  

Microsoft Academic Search

ABSTRACT Dinosaur extinction is still a major enigma,of Earth history. In this review article, extinctions in the geological record will be briefly mentioned. Many of the imaginative,theories for the extinction of the dinosaurs,will also be presented. Within the uniformitarian paradigm, the meteorite impact theory, once considered 'outrageous', now is the dominant theory. However, the volcanic theory is still believed by

Michael J. oard

204

A distinct dinosaur life history?  

Microsoft Academic Search

Five factors, mobile terrestrial lifestyle, oviparity, parental care, multi-year maturation and juvenile sociality, contribute to a distinct life history for Mesozoic dinosaurs in comparison to extant archosaurs and mammals. Upright, para-sagittal gait reflects several synapomorphies of Dinosauria, and wide histological sampling suggests that multi-year maturation typified dinosaurs across a range of body sizes. Fossil support for juvenile sociality exceeds that

David J. Varricchio

2011-01-01

205

What Killed the Dinosaurs?  

NSDL National Science Digital Library

At this site the question of the extinction of the dinosaurs takes the form of an interactive matrix. With the hypotheses in the left margin and the types of evidence along the bottom, the resulting squares are indicated in cases where the evidence supports the hypothesis. Students can click on hypotheses to view an animated description, click on an evidence element to get a definition, or click on a marked square in the grid to see how a particular piece of evidence supports a particular hypothesis. Hypotheses include asteroid impact, volcanism, mammal competition and continental drift while the listed evidence elements are rare metal, melted rock, fractured crystals, fossil record, lava flows, sea level, and impact crater.

2007-12-12

206

Extracellular Purines Promote the Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells to the Osteogenic and Adipogenic Lineages  

PubMed Central

Extracellular nucleotides are potent signaling molecules mediating cell-specific biological functions, mostly within the processes of tissue damage and repair and flogosis. We previously demonstrated that adenosine 5?-triphosphate (ATP) inhibits the proliferation of human bone marrow-derived mesenchymal stem cells (BM-hMSCs), while stimulating, in vitro and in vivo, their migration. Here, we investigated the effects of ATP on BM-hMSC differentiation capacity. Molecular analysis showed that ATP treatment modulated the expression of several genes governing adipogenic and osteoblastic (ie, WNT-pathway-related genes) differentiation of MSCs. Functional studies demonstrated that ATP, under specific culture conditions, stimulated adipogenesis by significantly increasing the lipid accumulation and the expression levels of the adipogenic master gene PPAR? (peroxisome proliferator-activated receptor-gamma). In addition, ATP stimulated osteogenic differentiation by promoting mineralization and expression of the osteoblast-related gene RUNX2 (runt-related transcription factor 2). Furthermore, we demonstrated that ATP stimulated adipogenesis via its triphosphate form, while osteogenic differentiation was induced by the nucleoside adenosine, resulting from ATP degradation induced by CD39 and CD73 ectonucleotidases expressed on the MSC membrane. The pharmacological profile of P2 purinergic receptors (P2Rs) suggests that adipogenic differentiation is mainly mediated by the engagement of P2Y1 and P2Y4 receptors, while stimulation of the P1R adenosine-specific subtype A2B is involved in adenosine-induced osteogenic differentiation. Thus, we provide new insights into molecular regulation of MSC differentiation. PMID:23259837

Zini, Roberta; Rossi, Lara; Salvestrini, Valentina; Ferrari, Davide; Manfredini, Rossella; Lemoli, Roberto M.

2013-01-01

207

Dinosaur peptides suggest mechanisms of protein survival  

E-print Network

Eleven collagen peptide sequences recovered from chemical extracts of dinosaur bones were mapped onto molecular models of the vertebrate collagen fibril derived from extant taxa. The dinosaur peptides localized to fibril ...

San Antonio, James D.

208

Giant European dinosaur found in Spain  

NSDL National Science Digital Library

Fossils of a giant Sauropod, found in Spain, reveal that Europe was home to giant dinosaurs in the Late Jurassic period -- about 150 million years ago. Giant dinosaurs have previously been found mainly in the New World and Africa.

American Association for the Advancement of Science (AAAS;)

2006-12-21

209

National Museum of Natural History: Dinosaur Exhibits  

NSDL National Science Digital Library

This site from the National Museum of Natural History's (NMNH) Department of Paleobiology offers an enticing peek into the Smithsonian's large dinosaur collection. Users can browse for their favorite dinosaur alphabetically, by dinosaur groups, or by period, and view photos that are accompanied by brief commentary. A Special Tours section offers an Anatomy Lesson, clickable views of Dinosaur Hall, and a Behind the Scenes look at paleobiologists at work. Additional resources include a Geologic Time Scale and a collection of related links.

1998-01-01

210

Simulating Dinosaur Digestion in the Classroom.  

ERIC Educational Resources Information Center

Describes an activity for use with a chapter on dinosaurs, prehistoric life, or digestion in which children make simulated dinosaur stomachs to gain hands-on experience about the theory of gastroliths, or stomach stones. Presents teacher information about the digestive processes in birds and dinosaurs. Discusses materials needed, objectives,…

Peczkis, Jan

1992-01-01

211

The origin and early radiation of dinosaurs  

Microsoft Academic Search

Dinosaurs were remarkably successful during the Mesozoic and one subgroup, birds, remain an important component of modern ecosystems. Although the extinction of non-avian dinosaurs at the end of the Cretaceous has been the subject of intense debate, comparatively little attention has been given to the origin and early evolution of dinosaurs during the Late Triassic and Early Jurassic, one of

Stephen L. Brusatte; Sterling J. Nesbitt; Randall B. Irmis; Richard J. Butler; Michael J. Benton; Mark A. Norell

2010-01-01

212

The Development of a Virtual Dinosaur Museum  

ERIC Educational Resources Information Center

The objective of this article is to study the network and virtual reality technologies for developing a virtual dinosaur museum, which provides a Web-learning environment for students of all ages and the general public to know more about dinosaurs. We first investigate the method for building the 3D dynamic models of dinosaurs, and then describe…

Tarng, Wernhuar; Liou, Hsin-Hun

2007-01-01

213

Thump, Thump, Thump ... How Dinosaurs Moved  

NSDL National Science Digital Library

This activity is a printable one-page PDF handout, which focuses on dinosaur movement. Using illustrations that compare a crocodile's hips to a dinosaur's, students answer a series of questions. Fun challenges, Animal Push-Ups and Reptile Races, help students better understand how a hole in the hip socket differentiates dinosaurs from other reptiles.

214

Newsflash! Dinosaur Pages at the UCMP  

NSDL National Science Digital Library

This site, sponsored by the University of California Museum of Paleontology, provides information on most classes of dinosaurs, arranged in outline form on the basis of evolutionary relationships. Links also lead to birds and their relationship with dinosaurs. Also, there is a link to flying reptiles, which are neither dinosaurs nor birds.

215

Measuring Dinosaur Speed from Trackways  

NSDL National Science Digital Library

By measuring the spacing of fossil footprints it is possible to estimate the speed of the trackmaker, but only after making several assumptions based on footprint size and the behavior of a wide range of living animals. A widely applied method for estimating speed from trackways was developed through the research of R. McNeill Alexander, an expert in biomechanics. This lab is a group exercise designed to lead students step-by-step through the methods and principles involved in estimating speed of movement from trackway data using Alexander's method. First students test the method on humans to see how accurate it is, and then they apply it to measurements taken from a variety of dinosaur trackways. This activity involves having students collect speed and footprint data on subjects while they are running and walking. The footprint data are analyzed and the speed estimates are compared to the actual measured speeds. Students then collect trackway measurements from published illustrations of dinosaur trackways to estimate dinosaur speeds. Students calculate the percent error for their experimental estimates and use this to interpret the results obtained from dinosaur trackways. Spreadsheets may be used to record and carry out the calculations in the analysis. Students are asked to discuss the significance of their results to ongoing debates over the physical capabilities of dinosaurs.

Bennington, Bret

216

T-Cell Lineage Determination  

PubMed Central

Summary T cells originate from hematopoietic stem cells (HSCs) in the bone marrow but complete their development in the thymus. HSCs give rise to a variety of non-renewing hematopoietic progenitors, among which a rare subset migrates to the thymus via the bloodstream. The earliest T-cell progenitors identified in the thymus are not T-lineage restricted but possess the ability to give rise to cells of many different lineages. Alternative lineage potentials are gradually lost as progenitors progress towards later developmental stages. Here, we review the early developmental events that might be involved in T-cell lineage fate determination, including the properties of possible thymus settling progenitors, their homing into the thymus, and their T-cell lineage specification and commitment. PMID:20969581

Yang, Qi; Bell, J. Jeremiah; Bhandoola, Avinash

2010-01-01

217

First dinosaurs from Saudi Arabia.  

PubMed

Dinosaur remains from the Arabian subcontinent are exceedingly rare, and those that have been documented manifest indeterminate affinities. Consequently the discovery of a small, but diagnostic, accumulation of elements from Campanian-Maastrichtian (~ 75 Ma) deposits in northwestern Saudi Arabia is significant because it constitutes the first taxonomically identifiable dinosaur material described from the Arabian Peninsula. The fossils include a series of possible lithostrotian titanosaur caudal vertebrae, and some isolated theropod marginal teeth that share unique character states and metric parameters (analyzed using multivariate statistical methods) with derived abelisaurids - this is the first justifiable example of a non-avian carnivorous dinosaur clade from Arabia. The recognition of titanosaurians and abelisaurids from Saudi Arabia extends the palaeogeographical range of these groups along the entire northern Gondwanan margin during the latest Cretaceous. Moreover, given the extreme paucity of coeval occurrences elsewhere, the Saudi Arabian fossils provide a tantalizing glimpse into dinosaurian assemblage diversity within the region. PMID:24386326

Kear, Benjamin P; Rich, Thomas H; Vickers-Rich, Patricia; Ali, Mohammed A; Al-Mufarreh, Yahya A; Matari, Adel H; Al-Massari, Abdu M; Nasser, Abdulaziz H; Attia, Yousry; Halawani, Mohammed A

2013-01-01

218

The earliest known sauropod dinosaur.  

PubMed

Sauropods were a very successful group of dinosaurs during the Jurassic and Cretaceous periods, but their earlier history is poorly known. Until now, the earliest reported sauropod bones were from the Early Jurassic, and the only tentative evidence of earlier sauropods was in the form of controversial footprints. Here we report the discovery of an incomplete sauropod skeleton from the Late Triassic period of Thailand, which provides the first osteological evidence of pre-Jurassic sauropods. This dinosaur is markedly different from prosauropods and substantiates theoretical predictions that there was a fairly long period of sauropod evolution during the Triassic. PMID:10993074

Buffetaut, E; Suteethorn, V; Cuny, G; Tong, H; Le Loeuff, J; Khansubha, S; Jongautchariyakul, S

2000-09-01

219

Dinosaur Tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas  

E-print Network

41 Dinosaur Tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Formation; Lower Cretaceous) of the Paluxy River, in what is now Dinosaur Valley State Park (Glen Rose: dinosaurs, ichnology, Glen Rose Formation, Texas, Cretaceous #12;42 Dinosaur tracksites of the Paluxy River

Falkingham, Peter

220

Dino Times! How Dinosaurs Lived  

NSDL National Science Digital Library

This activity focuses on dinosaur ecosystems. It includes information about the fossil remains scientists have uncovered in fossilized lakebeds in China, illustrations of eight plant and animal species discovered in Liaoning, China, and four "Eco-Quest" questions that prompt students to speculate about how these eight animals and plants lived together.

221

The new evolution of dinosaurs UAlberta research is challenging basic assumptions about dinosaurs and greatly  

E-print Network

The new evolution of dinosaurs UAlberta research is challenging basic assumptions about dinosaurs on the feathered dinosaur Anchiornis huxleyi (pictured above) are based on comparisons with the cellular that showed evidence of feathers. (Image: Julius Csotonyi) (Edmonton) On an afternoon in May, drivers zip

Machel, Hans

222

Assessing dinosaur growth patterns: a microscopic revolution.  

PubMed

Some of the longest standing questions in dinosaur paleontology pertain to their development. Did dinosaurs grow at slow rates similar to extant reptiles or rapidly similar to living birds and mammals? How did some forms attain gigantic proportions? Conversely, how did birds (avian dinosaurs) become miniaturized? New data on dinosaur longevity garnered from bone microstructure (i.e. osteohistology) are making it possible to assess basic life-history parameters of the dinosaurs such as growth rates and timing of developmental events. Analyses of these data in an evolutionary context are enabling the identification of developmental patterns that lead to size changes within the Dinosauria. Furthermore, this rich new database is providing inroads for studying individual and population biology. All in all, paleohistological research is proving to be the most promising avenue towards gaining a comprehensive understanding of dinosaur biology. PMID:16701457

Erickson, Gregory M

2005-12-01

223

Tramline Virtual Field Trips: Dinosaurs Field Trip  

NSDL National Science Digital Library

Hosted by Tramline Virtual Field Trips, this online field trip was created by educator Theresa Hughes-Feletar to teach young students (grades 1-3) about dinosaurs. Hughes-Feletar's virtual field trip links to a variety of quality websites about dinosaurs to create an integrated learning experience. The field trip links -- or Stops as the website refers to them -- provide information about dinosaur reproduction, fossils, hunting, extinction, and more. A supplemental Teacher's Resources page includes recommended book and music lists, as well as dinosaur curriculum ideas for subjects such as science, math, and art.

Hughes-Feletar, Theresa

224

New Developmental Evidence Clarifies the Evolution of Wrist Bones in the Dinosaur-Bird Transition  

PubMed Central

From early dinosaurs with as many as nine wrist bones, modern birds evolved to develop only four ossifications. Their identity is uncertain, with different labels used in palaeontology and developmental biology. We examined embryos of several species and studied chicken embryos in detail through a new technique allowing whole-mount immunofluorescence of the embryonic cartilaginous skeleton. Beyond previous controversy, we establish that the proximal–anterior ossification develops from a composite radiale+intermedium cartilage, consistent with fusion of radiale and intermedium observed in some theropod dinosaurs. Despite previous claims that the development of the distal–anterior ossification does not support the dinosaur–bird link, we found its embryonic precursor shows two distinct regions of both collagen type II and collagen type IX expression, resembling the composite semilunate bone of bird-like dinosaurs (distal carpal 1+distal carpal 2). The distal–posterior ossification develops from a cartilage referred to as “element x,” but its position corresponds to distal carpal 3. The proximal–posterior ossification is perhaps most controversial: It is labelled as the ulnare in palaeontology, but we confirm the embryonic ulnare is lost during development. Re-examination of the fossil evidence reveals the ulnare was actually absent in bird-like dinosaurs. We confirm the proximal–posterior bone is a pisiform in terms of embryonic position and its development as a sesamoid associated to a tendon. However, the pisiform is absent in bird-like dinosaurs, which are known from several articulated specimens. The combined data provide compelling evidence of a remarkable evolutionary reversal: A large, ossified pisiform re-evolved in the lineage leading to birds, after a period in which it was either absent, nonossified, or very small, consistently escaping fossil preservation. The bird wrist provides a modern example of how developmental and paleontological data illuminate each other. Based on all available data, we introduce a new nomenclature for bird wrist ossifications. PMID:25268520

Botelho, Joao Francisco; Ossa-Fuentes, Luis; Soto-Acuna, Sergio; Smith-Paredes, Daniel; Nunez-Leon, Daniel; Salinas-Saavedra, Miguel; Ruiz-Flores, Macarena; Vargas, Alexander O.

2014-01-01

225

New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition.  

PubMed

From early dinosaurs with as many as nine wrist bones, modern birds evolved to develop only four ossifications. Their identity is uncertain, with different labels used in palaeontology and developmental biology. We examined embryos of several species and studied chicken embryos in detail through a new technique allowing whole-mount immunofluorescence of the embryonic cartilaginous skeleton. Beyond previous controversy, we establish that the proximal-anterior ossification develops from a composite radiale+intermedium cartilage, consistent with fusion of radiale and intermedium observed in some theropod dinosaurs. Despite previous claims that the development of the distal-anterior ossification does not support the dinosaur-bird link, we found its embryonic precursor shows two distinct regions of both collagen type II and collagen type IX expression, resembling the composite semilunate bone of bird-like dinosaurs (distal carpal 1+distal carpal 2). The distal-posterior ossification develops from a cartilage referred to as "element x," but its position corresponds to distal carpal 3. The proximal-posterior ossification is perhaps most controversial: It is labelled as the ulnare in palaeontology, but we confirm the embryonic ulnare is lost during development. Re-examination of the fossil evidence reveals the ulnare was actually absent in bird-like dinosaurs. We confirm the proximal-posterior bone is a pisiform in terms of embryonic position and its development as a sesamoid associated to a tendon. However, the pisiform is absent in bird-like dinosaurs, which are known from several articulated specimens. The combined data provide compelling evidence of a remarkable evolutionary reversal: A large, ossified pisiform re-evolved in the lineage leading to birds, after a period in which it was either absent, nonossified, or very small, consistently escaping fossil preservation. The bird wrist provides a modern example of how developmental and paleontological data illuminate each other. Based on all available data, we introduce a new nomenclature for bird wrist ossifications. PMID:25268520

Botelho, João Francisco; Ossa-Fuentes, Luis; Soto-Acuña, Sergio; Smith-Paredes, Daniel; Nuñez-León, Daniel; Salinas-Saavedra, Miguel; Ruiz-Flores, Macarena; Vargas, Alexander O

2014-09-01

226

The Four-Winged Dinosaur  

NSDL National Science Digital Library

For this actiivty the students will watch a Nova documentary called "The Four-Winged Dinosaur." The documentary follows two teams of scientists as they create replicas of microraptor, a dinosaur with four feathered wings, in an attempt to determine how flight evolved in birds (from the ground up or from the trees down). As the students watch the video, they should think about each hypothesis and pay attention to the lines of evidence presented on both sides of the argument. The students are given specific questions to answer while watching the video that will help them pay attention to key ideas. Outside of class they are responsible for writing a short essay (~1 page, typed) describing which origin of flight hypothesis that they believe is the most plausible and why. Students must support their argument with evidence presented in the video.

Dunn, Tasha

227

GEOL 104 Dinosaurs: A Natural History Smithsonian Assignment II: Dinosaurs, Mesozoic Marine Life, and the Cenozoic Era (but mostly dinosaurs)  

E-print Network

's National Museum of Natural History (NMNH) has one of the largest collections of dinosaur and other fossils in the world. This exercise will concentrate on the wonderful dinosaur fossils on exhibit. The Smithsonian into the Hall of Fossil Mammals and Hall of Ice Age Mammals to get a glimpse at life after the Age

Holtz Jr., Thomas R.

228

Dinosaur Remains Found in Oregon  

NSDL National Science Digital Library

Two amateur paleontologists kept their eyes to the ground in Oregon on one of their recent hikes and discovered what are believed to be the first remains of a marine reptile called the plesiosaur to be unearthed in the Pacific Northwest. This radio broadcast reports on the discovery and what it could mean to the understanding of dinosaurs in the area. The clip is 5 minutes and 6 seconds in length.

229

First ceratosaurian dinosaur from Australia  

NASA Astrophysics Data System (ADS)

The basal theropod dinosaur clade Ceratosauria, and its subclade Abelisauroidea, is characteristic of late Mesozoic terrestrial vertebrate faunas in western Gondwana (South America, Africa, Madagascar, and India) and Europe. Yet unambiguous records of ceratosaurs have hitherto been absent from Australia, where the theropod assemblage appears to include several typically Laurasian clades. Here, we report the first evidence of ceratosaurs (and potentially abelisauroids) from eastern Gondwana--a diagnostic astragalocalcaneum from the Aptian (121-125 Ma) of Victoria, Australia. Ceratosauria thus occurred in both western and eastern Gondwana during the Early Cretaceous. This fossil adds to the poorly known dinosaur fauna of Australia, a major clade of basal theropods, emphasising that its mid-Cretaceous theropod diversity was surprisingly cosmopolitan despite relative geographic isolation, including clades that have been thought to be typical of both Gondwana and Laurasia--Ceratosauria, Spinosauridae, Carcharodontosauria, Tyrannosauroidea, and Deinonychosauria. Such a contemporaneous association of theropod clades is unknown from other Gondwanan continents and questions the views that the late Mesozoic dinosaur fauna of Australia was dominated by Gondwanan or Laurasian elements, extreme isolation, relictualism, and/or novelty as a `centre of origin'. The cosmopolitan theropod fauna of Australia probably reflects the global distribution of these clades early in their history, prior to significant continental breakup.

Fitzgerald, Erich M. G.; Carrano, Matthew T.; Holland, Timothy; Wagstaff, Barbara E.; Pickering, David; Rich, Thomas H.; Vickers-Rich, Patricia

2012-05-01

230

Q:China and dinosaurs: what's the connection?  

E-print Network

to China to study dinosaur out of, and what kind of changes happened to the eggs during the millionsQ:China and dinosaurs: what's the connection? China and dinosaurs: what's the connection? MSU N 10 by visiting Montana.edu/outreach Scientists discovered a four-winged dinosaur from China that was the size

231

Evidence of intestinal parasites of dinosaurs.  

PubMed

Protozoan cysts and helminth eggs preserved in a coprolite from the Early Cretaceous Bernissart Iguanodon shaft in Belgium demonstrate that representatives of 3 phyla parasitized dinosaurs by that period. These fossil parasite stages are described and their possible effect on dinosaurs discussed. These findings represent the earliest fossil records of protozoan and helminth parasites of terrestrial vertebrates. PMID:16623965

Poinar, G; Boucot, A J

2006-08-01

232

Dinosaur dynamics in the Jurassic Era  

NASA Astrophysics Data System (ADS)

Dinosaurs were fascinating animals and elicit much excitement in the classroom. Analysis of fossilized dinosaur trackways permits one to estimate the locomotion speeds and accelerations of these extinct beasts. Such analysis allows one to apply Newton's laws of motion to examples from the Jurassic Era.

Lee, Scott

2010-04-01

233

Early ornithischian dinosaurs: the Triassic record  

Microsoft Academic Search

Ornithischian dinosaurs are one of the most taxonomically diverse dinosaur clades during the Mesozoic, yet their origin and early diversification remain virtually unknown. In recent years, several new Triassic ornithischian taxa have been proposed, mostly based upon isolated teeth. New discoveries of skeletal material of some of these tooth taxa indicate that these teeth can no longer be assigned to

Randall B. Irmis; William G. Parker; Sterling J. Nesbitt; Jun Liu

2007-01-01

234

The Evolution of Dinosaurs Over Geologic Time  

NSDL National Science Digital Library

This lesson plan asks high school students to combine their knowledge of evolution, geologic time, and dinosaurs into a discussion of how these three topics overlap with regard to dinosaur evolution in the Cretaceous period. Students will read about the work of paleontologist Paul Sereno and list the dinosaurs he has discovered as well as the locations in which they were found and the time periods in which they lived; review the periods of geologic time; review the theory of evolution and write a paragraph explaining how geographic isolation would contribute to the evolutionary process; write paragraphs describing the changes to the continental layout of the Earth during the Cretaceous period; write paragraphs relating geological changes to dinosaur evolution during the Cretaceous period; and create posters or computer presentations illustrating the Earth during the Cretaceous period and the evolution processes of dinosaur species during this time.

235

The last polar dinosaurs: high diversity of latest Cretaceous arctic dinosaurs in Russia  

NASA Astrophysics Data System (ADS)

A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous-Tertiary mass extinction event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest Cretaceous dinosaur taxa could reproduce in polar region and were probably year-round residents of high latitudes. Palaeobotanical data suggest that these polar dinosaurs lived in a temperate climate (mean annual temperature about 10°C), but the climate was apparently too cold for amphibians and ectothermic reptiles. The high diversity of Late Maastrichtian dinosaurs in high latitudes, where ectotherms are absent, strongly questions hypotheses according to which dinosaur extinction was a result of temperature decline, caused or not by the Chicxulub impact.

Godefroit, Pascal; Golovneva, Lina; Shchepetov, Sergei; Garcia, Géraldine; Alekseev, Pavel

2009-04-01

236

Engraftment and Lineage Potential of Adult Hematopoietic Stem and Progenitor Cells Is Compromised Following Short-Term Culture in the Presence of an Aryl Hydrocarbon Receptor Antagonist  

PubMed Central

Abstract Hematopoietic stem cell gene therapy for HIV/AIDS is a promising alternative to lifelong antiretroviral therapy. One of the limitations of this approach is the number and quality of stem cells available for transplant following in vitro manipulations associated with stem cell isolation and genetic modification. The development of methods to increase the number of autologous, gene-modified stem cells available for transplantation would overcome this barrier. Hematopoietic stem and progenitor cells (HSPC) from adult growth factor-mobilized peripheral blood were cultured in the presence of an aryl hydrocarbon receptor antagonist (AhRA) previously shown to expand HSPC from umbilical cord blood. Qualitative and quantitative assessment of the hematopoietic potential of minimally cultured (MC-HSPC) or expanded HSPC (Exp-HSPC) was performed using an immunodeficient mouse model of transplantation. Our results demonstrate robust, multilineage engraftment of both MC-HSPC and Exp-HSPC although estimates of expansion based on stem cell phenotype were not supported by a corresponding increase in in vivo engrafting units. Bone marrow of animals transplanted with either MC-HSPC or Exp-HSPC contained secondary engrafting cells verifying the presence of primitive stem cells in both populations. However, the frequency of in vivo engrafting units among the more primitive CD34+/CD90+ HSPC population was significantly lower in Exp-HSPC compared with MC-HSPC. Exp-HSPC also produced fewer lymphoid progeny and more myeloid progeny than MC-HSPC. These results reveal that in vitro culture of adult HSPC in AhRA maintains but does not increase the number of in vivo engrafting cells and that HSPC expanded in vitro contain defects in lymphopoiesis as assessed in this model system. Further investigation is required before implementation of this approach in the clinical setting. PMID:25003230

Gu, Angel; Torres-Coronado, Monica; Tran, Chy-Anh; Vu, Hieu; Epps, Elizabeth W.; Chung, Janet; Gonzalez, Nancy; Blanchard, Suzette

2014-01-01

237

What Killed The Dinosaurs?: The Great Mystery  

NSDL National Science Digital Library

This site presents theories about why the dinosaurs became extinct. The first page provides background information covering not only the "great dying" at the K-T boundary but also the mass extinction at the end of the Paleozoic Era. The author covers six factors that complicate the study of mass extinction including time resolution, the Signor-Lipps Effect, and falsifiability. A link then takes the reader to a second page where invalid extinction hypotheses are explained. These range from "hay fever killed the dinosaurs" to "the dinosaurs just faded away," (no causation implied). The final link leads us to current thinking about extinction including volcanism, plate tectonics, and the Alvarez Hypothesis.

Hutchinson, John

238

Biology of the sauropod dinosaurs: the evolution of gigantism  

PubMed Central

The herbivorous sauropod dinosaurs of the Jurassic and Cretaceous periods were the largest terrestrial animals ever, surpassing the largest herbivorous mammals by an order of magnitude in body mass. Several evolutionary lineages among Sauropoda produced giants with body masses in excess of 50 metric tonnes by conservative estimates. With body mass increase driven by the selective advantages of large body size, animal lineages will increase in body size until they reach the limit determined by the interplay of bauplan, biology, and resource availability. There is no evidence, however, that resource availability and global physicochemical parameters were different enough in the Mesozoic to have led to sauropod gigantism. We review the biology of sauropod dinosaurs in detail and posit that sauropod gigantism was made possible by a specific combination of plesiomorphic characters (phylogenetic heritage) and evolutionary innovations at different levels which triggered a remarkable evolutionary cascade. Of these key innovations, the most important probably was the very long neck, the most conspicuous feature of the sauropod bauplan. Compared to other herbivores, the long neck allowed more efficient food uptake than in other large herbivores by covering a much larger feeding envelope and making food accessible that was out of the reach of other herbivores. Sauropods thus must have been able to take up more energy from their environment than other herbivores. The long neck, in turn, could only evolve because of the small head and the extensive pneumatization of the sauropod axial skeleton, lightening the neck. The small head was possible because food was ingested without mastication. Both mastication and a gastric mill would have limited food uptake rate. Scaling relationships between gastrointestinal tract size and basal metabolic rate (BMR) suggest that sauropods compensated for the lack of particle reduction with long retention times, even at high uptake rates. The extensive pneumatization of the axial skeleton resulted from the evolution of an avian-style respiratory system, presumably at the base of Saurischia. An avian-style respiratory system would also have lowered the cost of breathing, reduced specific gravity, and may have been important in removing excess body heat. Another crucial innovation inherited from basal dinosaurs was a high BMR. This is required for fueling the high growth rate necessary for a multi-tonne animal to survive to reproductive maturity. The retention of the plesiomorphic oviparous mode of reproduction appears to have been critical as well, allowing much faster population recovery than in megaherbivore mammals. Sauropods produced numerous but small offspring each season while land mammals show a negative correlation of reproductive output to body size. This permitted lower population densities in sauropods than in megaherbivore mammals but larger individuals. Our work on sauropod dinosaurs thus informs us about evolutionary limits to body size in other groups of herbivorous terrestrial tetrapods. Ectothermic reptiles are strongly limited by their low BMR, remaining small. Mammals are limited by their extensive mastication and their vivipary, while ornithsichian dinosaurs were only limited by their extensive mastication, having greater average body sizes than mammals. PMID:21251189

Sander, P Martin; Christian, Andreas; Clauss, Marcus; Fechner, Regina; Gee, Carole T; Griebeler, Eva-Maria; Gunga, Hanns-Christian; Hummel, Jurgen; Mallison, Heinrich; Perry, Steven F; Preuschoft, Holger; Rauhut, Oliver W M; Remes, Kristian; Tutken, Thomas; Wings, Oliver; Witzel, Ulrich

2011-01-01

239

Stems  

NSDL National Science Digital Library

Some mature plants can produce new plants by cutting a piece of stem off of the original plant. Most members of the mint family and ivy family can do this readily. The new plant will grow its own root system.

Olivia Worland (Purdue University;Biological Sciences)

2008-06-03

240

An Evolutionary Cascade Model for Sauropod Dinosaur Gigantism - Overview, Update and Tests  

PubMed Central

Sauropod dinosaurs are a group of herbivorous dinosaurs which exceeded all other terrestrial vertebrates in mean and maximal body size. Sauropod dinosaurs were also the most successful and long-lived herbivorous tetrapod clade, but no abiological factors such as global environmental parameters conducive to their gigantism can be identified. These facts justify major efforts by evolutionary biologists and paleontologists to understand sauropods as living animals and to explain their evolutionary success and uniquely gigantic body size. Contributions to this research program have come from many fields and can be synthesized into a biological evolutionary cascade model of sauropod dinosaur gigantism (sauropod gigantism ECM). This review focuses on the sauropod gigantism ECM, providing an updated version based on the contributions to the PLoS ONE sauropod gigantism collection and on other very recent published evidence. The model consist of five separate evolutionary cascades (“Reproduction”, “Feeding”, “Head and neck”, “Avian-style lung”, and “Metabolism”). Each cascade starts with observed or inferred basal traits that either may be plesiomorphic or derived at the level of Sauropoda. Each trait confers hypothetical selective advantages which permit the evolution of the next trait. Feedback loops in the ECM consist of selective advantages originating from traits higher in the cascades but affecting lower traits. All cascades end in the trait “Very high body mass”. Each cascade is linked to at least one other cascade. Important plesiomorphic traits of sauropod dinosaurs that entered the model were ovipary as well as no mastication of food. Important evolutionary innovations (derived traits) were an avian-style respiratory system and an elevated basal metabolic rate. Comparison with other tetrapod lineages identifies factors limiting body size. PMID:24205267

Sander, P. Martin

2013-01-01

241

Flow Cytometry Reveals that H5N1 Vaccination Elicits Cross-Reactive Stem-Directed Antibodies from Multiple Ig Heavy-Chain Lineages  

PubMed Central

ABSTRACT An understanding of the antigen-specific B-cell response to the influenza virus hemagglutinin (HA) is critical to the development of universal influenza vaccines, but it has not been possible to examine these cells directly because HA binds to sialic acid (SA) on most cell types. Here, we use structure-based modification of HA to isolate HA-specific B cells by flow cytometry and characterize the features of HA stem antibodies (Abs) required for their development. Incorporation of a previously described mutation (Y98F) to the receptor binding site (RBS) causes HA to bind only those B cells that express HA-specific Abs, but it does not bind nonspecifically to B cells, and this mutation has no effect on the binding of broadly neutralizing Abs to the RBS. To test the specificity of the Y98F mutation, we first demonstrated that previously described HA nanoparticles mediate hemagglutination and then determined that the Y98F mutation eliminates this activity. Cloning of immunoglobulin genes from HA-specific B cells isolated from a single human subject demonstrates that vaccination with H5N1 influenza virus can elicit B cells expressing stem monoclonal Abs (MAbs). Although these MAbs originated mostly from the IGHV1-69 germ line, a reasonable proportion derived from other genes. Analysis of stem Abs provides insight into the maturation pathways of IGVH1-69-derived stem Abs. Furthermore, this analysis shows that multiple non-IGHV1-69 stem Abs with a similar neutralizing breadth develop after vaccination in humans, suggesting that the HA stem response can be elicited in individuals with non-stem-reactive IGHV1-69 alleles. IMPORTANCE Universal influenza vaccines would improve immune protection against infection and facilitate vaccine manufacturing and distribution. Flu vaccines stimulate B cells in the blood to produce antibodies that neutralize the virus. These antibodies target a protein on the surface of the virus called HA. Flu vaccines must be reformulated annually, because these antibodies are mostly specific to the viral strains used in the vaccine. But humans can produce broadly neutralizing antibodies. We sought to isolate B cells whose genes encode influenza virus antibodies from a patient vaccinated for avian influenza. To do so, we modified HA so it would bind only the desired cells. Sequencing the antibody genes of cells marked by this probe proved that the patient produced broadly neutralizing antibodies in response to the vaccine. Many sequences obtained had not been observed before. There are more ways to generate broadly neutralizing antibodies for influenza virus than previously thought. PMID:24501410

Whittle, James R. R.; Wheatley, Adam K.; Wu, Lan; Lingwood, Daniel; Kanekiyo, Masaru; Ma, Steven S.; Narpala, Sandeep R.; Yassine, Hadi M.; Frank, Gregory M.; Yewdell, Jonathan W.; Ledgerwood, Julie E.; Wei, Chih-Jen; McDermott, Adrian B.; Graham, Barney S.; Koup, Richard A.

2014-01-01

242

The Science of Digging Up Dinosaurs  

NSDL National Science Digital Library

This activity has students trace the steps of a paleontologist from determining where to look for dinosaur fossils to studying the completed dinosaur skeleton for clues about the dinosaurs' behavior, diet, and anatomy. To start, students list and discuss the things they know about paleontology and then brainstorm what they think would be the most and least interesting aspects of being a paleontologist. Then they read about Paul Serenos' activities and discoveries, list his dinosaur findings and locations, read about the processes involved in paleontology, and explain why these steps are important. Lastly students prepare a report in which they write and share with the class detailed plans explaining specific parts of the fossil location, excavation, transportation, and research processes. This site provides twelve links to aid students in their research and five more for further investigation. It also has suggestions for assessment and ideas for extending the lesson.

243

101 Crazy Theories About Dinosaur Extinction  

NSDL National Science Digital Library

This document presents a number of theories, both plausible and implausible or even humorous, for the extinction of the dinosaurs. Links to a glossary are embedded in the text. A reading list and links to related sites are also provided.

244

Fossils 1: Fossils and Dinosaurs  

NSDL National Science Digital Library

In this lesson, students will understand what can be learned from fossils and in doing so, realize the difference between fact and theory. This lesson is the first of a two-part series on fossils. These lessons will go beyond naming dinosaurs and give students a broad understanding of how we know about the great beasts. They will start to acquire knowledge of the fossil record in preparation for learning about evolution and natural selection, concepts they will study in high school. This particular lesson focuses on what we have learned and can learn from fossils. In the first part, students will discuss what we know about horses. They will then do the same for a Stegosaurus. Another part of the lesson briefly covers how fossils are formed.

245

ESTIMATING SPEEDS OF DINOSAURS FROM TRACKWAYS: A REEVALUATION OF ASSUMPTIONS  

Microsoft Academic Search

For 30 years, using equations determined by Alexander (1976), paleontologists have estimated speeds of dinosaurs from their trackways; the fundamental assumption, based on limited observations, was that dinosaur hip height is approximately four times foot length. Thulborn (1990) subsequently determined that the leg length to foot length ratio ranges from 4.5-6.0, according to type and size of dinosaur. Given that

Emma C. Rainforth; Melissa Manzella

246

A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago  

Microsoft Academic Search

Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the

Ursula B. Göhlich; Luis M. Chiappe

2006-01-01

247

The Great Dinosaur Feud: Science against All Odds  

ERIC Educational Resources Information Center

In the 19th century, the race to uncover dinosaur fossils and name new dinosaur species inspired two rival scientists, Edward Drinker Cope and Othniel Charles Marsh, to behave in ways that were the antithesis of scientific methods. Subterfuge, theft, and espionage were the ingredients of the Great Dinosaur Feud. Because students often enjoy…

Clary, Renee; Wandersee, James; Carpinelli, Amy

2008-01-01

248

SUMO-Specific Protease 2 Is Essential for Modulating p53-Mdm2 in Development of Trophoblast Stem Cell Niches and Lineages  

PubMed Central

SUMO-specific protease 2 (SENP2) modifies proteins by removing SUMO from its substrates. Although SUMO-specific proteases are known to reverse sumoylation in many defined systems, their importance in mammalian development and pathogenesis remains largely elusive. Here we report that SENP2 is highly expressed in trophoblast cells that are required for placentation. Targeted disruption of SENP2 in mice reveals its essential role in development of all three trophoblast layers. The mutation causes a deficiency in cell cycle progression. SENP2 has a specific role in the G–S transition, which is required for mitotic and endoreduplication cell cycles in trophoblast proliferation and differentiation, respectively. SENP2 ablation disturbs the p53–Mdm2 pathway, affecting the expansion of trophoblast progenitors and their maturation. Reintroducing SENP2 into the mutants can reduce the sumoylation of Mdm2, diminish the p53 level and promote trophoblast development. Furthermore, downregulation of p53 alleviates the SENP2-null phenotypes and stimulation of p53 causes abnormalities in trophoblast proliferation and differentiation, resembling those of the SENP2 mutants. Our data reveal a key genetic pathway, SENP2–Mdm2–p53, underlying trophoblast lineage development, suggesting its pivotal role in cell cycle progression of mitosis and endoreduplication. PMID:19090619

Chiu, Shang-Yi; Asai, Naoya; Costantini, Frank; Hsu, Wei

2008-01-01

249

Dinosaurs  

NSDL National Science Digital Library

This activity, designed to simulate an archeological dig, allows students to experience the difficulties when interpreting an archeological discovery. They will demonstrate an understanding of model building, use problem solving to put unknown entities together in a sequential manner, and answer questions related to an organisms structural and/or anatomical design, possible habitat, and way of securing food.

1998-01-01

250

VEGFA-dependent and -independent pathways synergise to drive Scl expression and initiate programming of the blood stem cell lineage in Xenopus  

PubMed Central

The first haematopoietic stem cells share a common origin with the dorsal aorta and derive from putative adult haemangioblasts in the dorsal lateral plate (DLP) mesoderm. Here we show that the transcription factor (TF) stem cell leukaemia (Scl/Tal1) is crucial for development of these adult haemangioblasts in Xenopus and establish the regulatory cascade controlling its expression. We show that VEGFA produced in the somites is required to initiate adult haemangioblast programming in the adjacent DLP by establishing endogenous VEGFA signalling. This response depends on expression of the VEGF receptor Flk1, driven by Fli1 and Gata2. Scl activation requires synergy between this VEGFA-controlled pathway and a VEGFA-independent pathway controlled by Fli1, Gata2 and Etv2/Etsrp/ER71, which also drives expression of the Scl partner Lmo2. Thus, the two ETS factors Fli1 and Etv6, which drives the VEGFA expression in both somites and the DLP, sit at the top of the adult haemangioblast gene regulatory network (GRN). Furthermore, Gata2 is initially activated by Fli1 but later maintained by another ETS factor, Etv2. We also establish that Flk1 and Etv2 act independently in the two pathways to Scl activation. Thus, detailed temporal, epistatic measurements of key TFs and VEGFA plus its receptor have enabled us to build a Xenopus adult haemangioblast GRN. PMID:23637333

Ciau-Uitz, Aldo; Pinheiro, Philip; Kirmizitas, Arif; Zuo, Jie; Patient, Roger

2013-01-01

251

Forearm Posture and Mobility in Quadrupedal Dinosaurs  

PubMed Central

Quadrupedality evolved four independent times in dinosaurs; however, the constraints associated with these transitions in limb anatomy and function remain poorly understood, in particular the evolution of forearm posture and rotational ability (i.e., active pronation and supination). Results of previous qualitative studies are inconsistent, likely due to an inability to quantitatively assess the likelihood of their conclusions. We attempt to quantify antebrachial posture and mobility using the radius bone because its morphology is distinct between extant sprawled taxa with a limited active pronation ability and parasagittal taxa that have an enhanced ability to actively pronate the manus. We used a sliding semi-landmark, outline-based geometric morphometric approach of the proximal radial head and a measurement of the angle of curvature of the radius in a sample of 189 mammals, 49 dinosaurs, 35 squamates, 16 birds, and 5 crocodilians. Our results of radial head morphology showed that quadrupedal ceratopsians, bipedal non-hadrosaurid ornithopods, and theropods had limited pronation/supination ability, and sauropodomorphs have unique radial head morphology that likely allowed limited rotational ability. However, the curvature of the radius showed that no dinosaurian clade had the ability to cross the radius about the ulna, suggesting parallel antebrachial elements for all quadrupedal dinosaurs. We conclude that the bipedal origins of all quadrupedal dinosaur clades could have allowed for greater disparity in forelimb posture than previously appreciated, and future studies on dinosaur posture should not limit their classifications to the overly simplistic extant dichotomy. PMID:24058633

VanBuren, Collin S.; Bonnan, Matthew

2013-01-01

252

Pax6 is essential for the maintenance and multi-lineage differentiation of neural stem cells, and for neuronal incorporation into the adult olfactory bulb.  

PubMed

The paired type homeobox 6 (Pax6) transcription factor (TF) regulates multiple aspects of neural stem cell (NSC) and neuron development in the embryonic central nervous system. However, less is known about the role of Pax6 in the maintenance and differentiation of adult NSCs and in adult neurogenesis. Using the +/Sey(Dey) mouse, we have analyzed how Pax6 heterozygosis influences the self-renewal and proliferation of adult olfactory bulb stem cells (aOBSCs). In addition, we assessed its influence on neural differentiation, neuronal incorporation, and cell death in the adult OB, both in vivo and in vitro. Our results indicate that the Pax6 mutation alters Nestin(+)-cell proliferation in vivo, as well as self-renewal, proliferation, and survival of aOBSCs in vitro although a subpopulation of +/Sey(Dey) progenitors is able to expand partially similar to wild-type progenitors. This mutation also impairs aOBSC differentiation into neurons and oligodendrocytes, whereas it increases cell death while preserving astrocyte survival and differentiation. Furthermore, Pax6 heterozygosis causes a reduction in the variety of neurochemical interneuron subtypes generated from aOBSCs in vitro and in the incorporation of newly generated neurons into the OB in vivo. Our findings support an important role of Pax6 in the maintenance of aOBSCs by regulating cell death, self-renewal, and cell fate, as well as in neuronal incorporation into the adult OB. They also suggest that deregulation of the cell cycle machinery and TF expression in aOBSCs which are deficient in Pax6 may be at the origin of the phenotypes observed in this adult NSC population. PMID:25117830

Curto, Gloria G; Nieto-Estévez, Vanesa; Hurtado-Chong, Anahí; Valero, Jorge; Gómez, Carmela; Alonso, José R; Weruaga, Eduardo; Vicario-Abejón, Carlos

2014-12-01

253

Sp1 Transcription Factor Interaction with Accumulated Prelamin A Impairs Adipose Lineage Differentiation in Human Mesenchymal Stem Cells: Essential Role of Sp1 in the Integrity of Lipid Vesicles  

PubMed Central

Lamin A (LMNA)-linked lipodystrophies may be either genetic (associated with LMNA mutations) or acquired (associated with the use of human immunodeficiency virus protease inhibitors [PIs]), and in both cases they share clinical features such as anomalous distribution of body fat or generalized loss of adipose tissue, metabolic alterations, and early cardiovascular complications. Both LMNA-linked lipodystrophies are characterized by the accumulation of the lamin A precursor prelamin A. The pathological mechanism by which prelamin A accumulation induces the lipodystrophy associated phenotypes remains unclear. Since the affected tissues in these disorders are of mesenchymal origin, we have generated an LMNA-linked experimental model using human mesenchymal stem cells treated with a PI, which recapitulates the phenotypes observed in patient biopsies. This model has been demonstrated to be a useful tool to unravel the pathological mechanism of the LMNA-linked lipodystrophies, providing an ideal system to identify potential targets to generate new therapies for drug discovery screening. We report for the first time that impaired adipogenesis is a consequence of the interaction between accumulated prelamin A and Sp1 transcription factor, sequestration of which results in altered extracellular matrix gene expression. In fact, our study shows a novel, essential, and finely tuned role for Sp1 in adipose lineage differentiation in human mesenchymal stem cells. These findings define a new physiological experimental model to elucidate the pathological mechanisms LMNA-linked lipodystrophies, creating new opportunities for research and treatment not only of LMNA-linked lipodystrophies but also of other adipogenesis-associated metabolic diseases. PMID:23197810

Ruiz de Eguino, Garbine; Infante, Arantza; Schlangen, Karin; Aransay, Ana M.; Fullaondo, Ane; Soriano, Mario; Garcia-Verdugo, Jose Manuel; Martin, Angel G.

2012-01-01

254

Ectoderm to Mesoderm Lineage Switching During Axolotl Tail Regeneration  

Microsoft Academic Search

Foreign environments may induce adult stem cells to switch lineages and populate multiple tissue types, but whether this mechanism is used for tissue repair remains uncertain. Urodele amphibians can regenerate fully functional, multitissue structures including the limb and tail. To determine whether lineage switching is an integral feature of this regeneration, we followed individual spinal cord cells live during tail

Karen Echeverri; Elly M. Tanaka

2002-01-01

255

Genomic Variability within an Organism Exposes Its Cell Lineage Tree  

Microsoft Academic Search

What is the lineage relation among the cells of an organism? The answer is sought by developmental biology, immunology, stem cell research, brain research, and cancer research, yet complete cell lineage trees have been reconstructed only for simple organisms such as Caenorhabditis elegans. We discovered that somatic mutations accumulated during normal development of a higher organism implicitly encode its entire

Dan Frumkin; Adam Wasserstrom; Shai Kaplan; Uriel Feige; Ehud Shapiro

2005-01-01

256

Control of a robot dinosaur  

PubMed Central

The Palaiomation Consortium, supported by the European Commission, is building a robot Iguanodon atherfieldensis for museum display that is much more sophisticated than existing animatronic exhibits. The current half-size (2.5 m) prototype is fully autonomous, carrying its own computer and batteries. It walks around the room, choosing its own path and avoiding obstacles. A bigger version with a larger repertoire of behaviours is planned. Many design problems have had to be overcome. A real dinosaur would have had hundreds of muscles, and we have had to devise means of achieving life-like movement with a much smaller number of motors; we have limited ourselves to 20, to keep the control problems manageable. Realistic stance requires a narrower trackway and a higher centre of mass than in previous (often spider-like) legged robots, making it more difficult to maintain stability. Other important differences from previous walking robots are that the forelegs have to be shorter than the hind, and the machinery has had to be designed to fit inside a realistically shaped body shell. Battery life is about one hour, but to achieve this we have had to design the robot to have very low power consumption. Currently, this limits it to unrealistically slow movement. The control system includes a high-level instructions processor, a gait generator, a motion-coordination generator, and a kinematic model.

Papantoniou, V.

1999-01-01

257

Important new dinosaur located in Utah  

NSDL National Science Digital Library

Recently, a team of researchers in a remote area of eastern Utah led by Utah state paleontologist James I. Kirkland made an important discovery that has been described as a type of dinosaur âÂÂmissing linkâÂÂ. Essentially, this âÂÂlinkâ represents a rather primitive plant-eater that evolved from the meat-eating raptors that also gave rise to modern birds. The dinosaur has been named Falcarius utahensis, which means âÂÂsickle-maker from UtahâÂÂ, largely due to its claws. The results of this important find were documented in this ThursdayâÂÂs edition of the journal Nature, and this material supports earlier contentions that link the plant-eating dinosaurs known as therizinosaurs to raptors. Matthew Lamanna from the Carnegie Museum of Natural History remarked that âÂÂItâÂÂs an extremely significant find. Before this discovery, the oldest known animal recognized as a therizinosaur came from China, and this one is just as old and seems to be more primitive anatomically. It appears to be the final piece of the puzzle.âÂÂThe first link leads to an article from this WednesdayâÂÂs Washington Post that offers some perspective on the find from the paleontologist James I. Kirkland. The second link will take visitors to a fine news story from the National GeographicâÂÂs website that provides a good perspective on this important discovery. The third link offers some informed insights from NatureâÂÂs own Michael Hopkins on this discovery. The fourth link leads to a very informative site from BBC on dinosaurs, which includes fact files on a number of dinosaurs, a timeline, and some interactive games and screensavers. The fifth link will take visitors to a very useful FAQ site, offered by the United States Geological Survey, which answers a number of common queries about dinosaurs, such as âÂÂWhere did dinosaurs live?â and âÂÂDid dinosaurs communicate?âÂÂ. The final link leads to the homepage of that noted University of Chicago paleontologist, Paul Sereno. Here visitors can learn about his work and expeditions, among other things.

258

Palaeontology: parental care in an ornithischian dinosaur.  

PubMed

Crocodilians and birds show extensive parental care of their young, but whether this behaviour evolved independently in these two groups of living archosaurs is unknown - in part because features of parenting among related fossil groups such as dinosaurs are unclear. A dramatic specimen of the small ornithischian dinosaur Psittacosaurus sp. (Dalian Natural History Museum D2156) from Liaoning in China reveals a single adult clustered with 34 juveniles within an area of 0.5 square metres, providing strong evidence for post-hatching parental care in Dinosauria. PMID:15356619

Meng, Qingjin; Liu, Jinyuan; Varricchio, David J; Huang, Timothy; Gao, Chunling

2004-09-01

259

Geochemical and mineralogical studies of dinosaur bone from the Morrison Formation at Dinosaur Ridge  

USGS Publications Warehouse

The dinosaur bones first discovered in 1877 in the Upper Jurassic Morrison Formation at Morrison, Colorado were the first major find of dinosaur skeletons in the western U.S. and led to the recognition of four new dinosaur genera (Apatosaurus, Allosaurus, Diplodocus, and Stegosaurus). Eight articles dealing with these bones which appeared as research reports in the annual reports of the Friends of Dinosaur Ridge from 1990-1999 are condensed and summarized with some additional comments. Two of the articles are about the mineralogy and preservation of the bones; two are about the physical description of the bone occurrence; two are about the history of the site, and two are about use of novel instrumental methods (ground-penetrating radar and a directional scintillometer) to search for new bones.

Modreski, P.J.

2001-01-01

260

Conserved loci of leaf and stem rust fungi of wheat share synteny interrupted by lineage-specific influx of repeat elements  

PubMed Central

Background Wheat leaf rust (Puccinia triticina Eriks; Pt) and stem rust fungi (P. graminis f.sp. tritici; Pgt) are significant economic pathogens having similar host ranges and life cycles, but different alternate hosts. The Pt genome, currently estimated at 135 Mb, is significantly larger than Pgt, at 88 Mb, but the reason for the expansion is unknown. Three genomic loci of Pt conserved proteins were characterized to gain insight into gene content, genome complexity and expansion. Results A bacterial artificial chromosome (BAC) library was made from P. triticina race 1, BBBD and probed with Pt homologs of genes encoding two predicted Pgt secreted effectors and a DNA marker mapping to a region of avirulence. Three BACs, 103 Kb, 112 Kb, and 166 Kb, were sequenced, assembled, and open reading frames were identified. Orthologous genes were identified in Pgt and local conservation of gene order (microsynteny) was observed. Pairwise protein identities ranged from 26 to 99%. One Pt BAC, containing a RAD18 ortholog, shares syntenic regions with two Pgt scaffolds, which could represent both haplotypes of Pgt. Gene sequence is diverged between the species as well as within the two haplotypes. In all three BAC clones, gene order is locally conserved, however, gene shuffling has occurred relative to Pgt. These regions are further diverged by differing insertion loci of LTR-retrotransposon, Gypsy, Copia, Mutator, and Harbinger mobile elements. Uncharacterized Pt open reading frames were also found; these proteins are high in lysine and similar to multiple proteins in Pgt. Conclusions The three Pt loci are conserved in gene order, with a range of gene sequence divergence. Conservation of predicted haustoria expressed secreted protein genes between Pt and Pgt is extended to the more distant poplar rust, Melampsora larici-populina. The loci also reveal that genome expansion in Pt is in part due to higher occurrence of repeat-elements in this species. PMID:23356831

2013-01-01

261

STAT5 requires the N-domain to maintain hematopoietic stem cell repopulating function and appropriate lymphoid-myeloid lineage output  

PubMed Central

Objective STAT5 is a critical regulator of hematopoietic development and its impaired activation is associated with hematopoietic and immune cell defects. However, much of this information has been learned from knockout mice that still retain the potential for expression of STAT5 proteins that are N-terminally truncated due to alternative internal translation initiation codons. The goal of these studies was to use transplantation based assays to analyze the degree of STAT5?N activity in HSC and throughout lymphomyeloid development. Methods We have directly compared E14.5 fetal liver cells from mice with potential to express STAT5ab?N (STAT5ab?N/?N) with mice completely lacking STAT5a and STAT5b (STAT5abnull/null). We have also utilized retroviral complementation of STAT5abnull/null fetal liver hematopoietic stem cells (HSC) to enforce expression of full-length STAT5a or STAT5a lacking the first 136 amino acids (STAT5a? N). Results We report that STAT5 is required for HSC, lymphocyte, and erythrocyte development. We demonstrate that restored expression of STAT5a in STAT5abnull/null HSC provides a strong selective advantage, correcting T/B lymphocyte and erythrocyte development. Interestingly, Gr-1+ blood cells were inversely correlated with B-lymphocytes and both were normalized by STAT5a expression. In contrast, transduction of STAT5a?N only provided partial B-lymphocyte development. Conclusions These studies define the role of STAT5 in maintaining normal lymphoid vs. myeloid balance during hematopoiesis and highlight a major role for the N/domain in HSC function. The platform of retroviral complementation described here will be particularly useful for future studies to sub-define the N-domain regions that are critical for hematopoiesis. PMID:17976521

Li, Geqiang; Wang, Zhengqi; Zhang, Yi; Kang, Zizhen; Haviernikova, Eleonora; Cui, Yongzhi; Hennighausen, Lothar; Moriggl, Richard; Wang, Demin; Tse, William; Bunting, Kevin D.

2007-01-01

262

New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism  

PubMed Central

Background During much of the Late Cretaceous, a shallow, epeiric sea divided North America into eastern and western landmasses. The western landmass, known as Laramidia, although diminutive in size, witnessed a major evolutionary radiation of dinosaurs. Other than hadrosaurs (duck-billed dinosaurs), the most common dinosaurs were ceratopsids (large-bodied horned dinosaurs), currently known only from Laramidia and Asia. Remarkably, previous studies have postulated the occurrence of latitudinally arrayed dinosaur “provinces,” or “biomes,” on Laramidia. Yet this hypothesis has been challenged on multiple fronts and has remained poorly tested. Methodology/Principal Findings Here we describe two new, co-occurring ceratopsids from the Upper Cretaceous Kaiparowits Formation of Utah that provide the strongest support to date for the dinosaur provincialism hypothesis. Both pertain to the clade of ceratopsids known as Chasmosaurinae, dramatically increasing representation of this group from the southern portion of the Western Interior Basin of North America. Utahceratops gettyi gen. et sp. nov.—characterized by short, rounded, laterally projecting supraorbital horncores and an elongate frill with a deep median embayment—is recovered as the sister taxon to Pentaceratops sternbergii from the late Campanian of New Mexico. Kosmoceratops richardsoni gen. et sp. nov.—characterized by elongate, laterally projecting supraorbital horncores and a short, broad frill adorned with ten well developed hooks—has the most ornate skull of any known dinosaur and is closely allied to Chasmosaurus irvinensis from the late Campanian of Alberta. Conclusions/Significance Considered in unison, the phylogenetic, stratigraphic, and biogeographic evidence documents distinct, co-occurring chasmosaurine taxa north and south on the diminutive landmass of Laramidia. The famous Triceratops and all other, more nested chasmosaurines are postulated as descendants of forms previously restricted to the southern portion of Laramidia. Results further suggest the presence of latitudinally arrayed evolutionary centers of endemism within chasmosaurine ceratopsids during the late Campanian, the first documented occurrence of intracontinental endemism within dinosaurs. PMID:20877459

Sampson, Scott D.; Loewen, Mark A.; Farke, Andrew A.; Roberts, Eric M.; Forster, Catherine A.; Smith, Joshua A.; Titus, Alan L.

2010-01-01

263

A beaver buddy for the dinosaurs?  

NSDL National Science Digital Library

Wouldn't it be cool to go back in time and see what things looked like 164 million years ago? Those were the days of the dinosaurs, which is why scientists digging in China were so surprised when they found a new animal fossil from that time that looks a lot like a beaver!

American Association for the Advancement of Science (AAAS;)

2006-02-23

264

Large Mesozoic mammals fed on young dinosaurs  

E-print Network

dinosaurs Yaoming Hu1,2,3 , Jin Meng2 , Yuanqing Wang1 & Chuankui Li1 1 Institute of Vertebrate Paleontology & Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China 2 Division of Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York City, New York 10024, USA 3

Sullivan, Jack

265

Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)  

Microsoft Academic Search

Ankylosauria is a diverse clade of quadrupedal ornithischian dinosaurs whose remains are known from Middle Jurassic to latest Cretaceous sediments worldwide. Despite a long history of research, ankylosaur interrelationships remain poorly resolved and existing cladistic analyses suffer from limited character and taxon sampling. Here, we present the most comprehensive phylogenetic analysis of the group attempted to date. The traditional ankylosaurid–nodosaurid

Richard S. Thompson; Jolyon C. Parish; Susannah C. R. Maidment; Paul M. Barrett

2011-01-01

266

Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)  

Microsoft Academic Search

Ankylosauria is a diverse clade of quadrupedal ornithischian dinosaurs whose remains are known from Middle Jurassic to latest Cretaceous sediments worldwide. Despite a long history of research, ankylosaur interrelationships remain poorly resolved and existing cladistic analyses suffer from limited character and taxon sampling. Here, we present the most comprehensive phylogenetic analysis of the group attempted to date. The traditional ankylosaurid–nodosaurid

Richard S. Thompson; Jolyon C. Parish; Susannah C. R. Maidment; Paul M. Barrett

2012-01-01

267

A review of the dinosaurs from Kansas  

Microsoft Academic Search

Although Kansas is best known for an abundance of marine fossils from the Late Cretaceous, there may be up to 16 dinosaur records from the state. These are (in order of discovery): 1) the Mudge tracks from the Dakota Formation of Clay County; 2) the hadrosaur, Claosaurus agilis, from the Niobrara Chalk of Logan County; 3) the Snow track from

Gregory A. Liggett

2005-01-01

268

Fighting Dinosaurs: New Discoveries from Mongolia  

NSDL National Science Digital Library

This Web site, created to complement an American Museum of Natural History exhibition, reports on one of the most famous fossil finds in the world (the fighting dinosaurs of Mongolia) and other ancient animal fossils discovered in the Gobi Desert. Although the exhibit is closed, there is useful information on the fossil finds and three short video clips.

269

Tail and pelvis pathologies of ankylosaurian dinosaurs  

Microsoft Academic Search

Ankylosaurid dinosaurs had modified distal caudal vertebrae (the handle) and large terminal caudal osteoderms (the knob), which together form the tail club. The tail club may have been used as a weapon. Ankylosaur pelvic and caudal elements were surveyed for evidence of healing wounds that may indicate traumatic injury, and which could support clubbing behaviour. No pathologies were found in

Victoria M. Arbour; Philip J. Currie

2011-01-01

270

An unusual oviraptorosaurian dinosaur from China  

Microsoft Academic Search

Oviraptorosaurians are an unusual group of theropod dinosaurs, with highly specialized skulls. Here we report a new oviraptorosaurian, Incisivosaurus gauthieri, gen. et sp. nov., from the lowest part of the Lower Cretaceous Yixian Formation of China. This oviraptorosaurian displays a number of characters closer to more typical theropods, such as a low skull and toothed jaws, thus greatly reducing the

Xing Xu; Yen-Nien Cheng; Xiao-Lin Wang; Chun-Hsiang Chang

2002-01-01

271

Resources and energetics determined dinosaur maximal size  

PubMed Central

Some dinosaurs reached masses that were ?8 times those of the largest, ecologically equivalent terrestrial mammals. The factors most responsible for setting the maximal body size of vertebrates are resource quality and quantity, as modified by the mobility of the consumer, and the vertebrate's rate of energy expenditure. If the food intake of the largest herbivorous mammals defines the maximal rate at which plant resources can be consumed in terrestrial environments and if that limit applied to dinosaurs, then the large size of sauropods occurred because they expended energy in the field at rates extrapolated from those of varanid lizards, which are ?22% of the rates in mammals and 3.6 times the rates of other lizards of equal size. Of 2 species having the same energy income, the species that uses the most energy for mass-independent maintenance of necessity has a smaller size. The larger mass found in some marine mammals reflects a greater resource abundance in marine environments. The presumptively low energy expenditures of dinosaurs potentially permitted Mesozoic communities to support dinosaur biomasses that were up to 5 times those found in mammalian herbivores in Africa today. The maximal size of predatory theropods was ?8 tons, which if it reflected the maximal capacity to consume vertebrates in terrestrial environments, corresponds in predatory mammals to a maximal mass less than a ton, which is what is observed. Some coelurosaurs may have evolved endothermy in association with the evolution of feathered insulation and a small mass. PMID:19581600

McNab, Brian K.

2009-01-01

272

Introduction to Thyreophora: The Armored Dinosaurs  

NSDL National Science Digital Library

The Thyreophora are a group of small to quite large armored plant-eating dinosaurs. The most familiar are Stegosaurus and Ankylosaurus, though there were many others. The two earliest known, Scutellosaurus and Scelidosaurus along with the remaining two major groups Stegosauria and Ankylosauria are described on this site.

273

Dinosaur Body Temperatures Determined from Isotopic (13  

E-print Network

of the nonavian dinosaurs is the subject of debate. Previously, arguments have been made for both endothermic that derive the heat they need to function from the environment, rather than endothermic "warm-blooded" mam by modeling heat exchange by animals with the environment, sug- gesting that endothermic sauropods would have

Schöne, Bernd R.

274

Targeting of the B-lineage leukemia stem cells and their progeny with norcantharidin encapsulated liposomes modified with a novel CD19 monoclonal antibody 2E8 in vitro.  

PubMed

This study was aimed to generate a new agent, norcantharidin (NCTD) encapsulated liposomes modified with a novel murine anti-human CD19 monoclonal antibody 2E8 (2E8–NCTD–liposomes), to specifically target the B-lineage leukemia stem cells (B-LSCs) and their progeny in vitro. Our results have shown that the positive percentage of 2E8–NCTD–liposomes on CD19+ Nalm-6 cells was (95.82 ± 1.09)%, significantly higher than that on CD19- Molt-3 cells [(2.94 ± 0.07)%, P<0.01], demonstrated by using multiparameter flow cytometry. The IC50 of 2E8–NCTD–liposomes on Nalm-6 cells using MTT assay was 14.52 µM, which was significantly lower than that on Molt-3 cells (45.89 µM, P < 0.01). The confocal microscopy and multiparameter flow cytometry analyses revealed that the internalization of 2E8–NCTD–liposomes into the cells and subsequently the release of NCTD into the cytoplasm to induce the apoptosis of B cells were responsible for specific cytotoxicity to the cells targeted. Real-time RT-PCR showed that the immunoliposomes were able to induce the apoptosis of B-LSCs via down-regulating the HLF and up-regulating the NFIL3 (nuclear factor, IL3 regulated) expressions at the mRNA level. Our conclusion is that 2E8–NCTD–liposome is a promising agent for selectively eradicating the B-LSCs and their progeny in vitro which warrants further studies in vivo. PMID:20222850

Zhang, Jingying; Tang, Yongmin; Li, Sisi; Liao, Chan; Guo, Xiaoping

2010-11-01

275

Developmental Cell Sox2+ Stem Cells Contribute  

E-print Network

as a marker for the dental epithelial stem cells will facilitate further studies on their lineage segregationDevelopmental Cell Article Sox2+ Stem Cells Contribute to All Epithelial Lineages of the Tooth via and Department of Stem Cell and Regenerative Biology, Harvard University and Harvard Medical School, 7 Divinity

Klein, Ophir

276

Discover Dinosaurs Paleontology at the American Museum of Natural History  

NSDL National Science Digital Library

This activity sheet for young children is designed to be completed during a visit to the Museum's fourth floor Fossil Halls. The printable two-page handout includes notes about how paleontologists use tools to find and dig out fossils, a scavenger hunt in the Hall of Saurischian Dinosaurs for two vegetarian dinosaurs, a scavenger hunt for protective body parts in the Hall of Ornithischian Dinosaurs and a collection of fun facts.

277

Multiple bottlenecks, allopatric lineages and Badlands bison Bos bison: Consequences of lineage mixing  

Microsoft Academic Search

While ecological and conservation consequences of combining animals of varied genetic backgrounds have been widely discussed, the demonstration of effects that stem from lineage mixing remains elusive. Since management agencies relocate populations or supplement them with individuals regularly, the opportunity for either inbreeding or outbreeding depression may be high; still, any putative effects will go unnoticed without detailed knowledge of

Joel Berger; Carol Cunningham

1995-01-01

278

The Great Dinosaur Feud: Science Against All Odds  

NSDL National Science Digital Library

In the 19th century, the race to uncover dinosaur fossils and name new dinosaur species inspired two rival scientists, Edward Drinker Cope and Othniel Charles Marsh, to behave in ways that were the antithesis of scientific methods. Subterfuge, theft, and espionage were the ingredients of the Great Dinosaur Feud. Because students often enjoy controversy, as evidenced by popular television programs today, the authors use the controversy of the dinosaur feud to illustrate the human side of science, and the triumph of science in spite of inappropriate competition.

Carpinelli, Amy; Wandersee, James; Clary, Renee

2008-10-01

279

The second Jurassic dinosaur rush and the dawn of dinomania.  

PubMed

During the second Jurassic dinosaur rush museum paleontologists raced to display the world's first mounted sauropod dinosaur. The American Museum of Natural History triumphed in 1905 when its Brontosaurus debuted before an admiring crowd of wealthy New Yorkers. The Carnegie Museum of Natural History in Pittsburgh, the Field Columbian Museum in Chicago and other institutions were quick to follow with their own sauropod displays. Thereafter, dinomania spread far and wide, and big, showpiece dinosaurs became a museum staple. This brief but intensely competitive period of acquisitiveness fostered important Jurassic dinosaur revisions and crucial innovations in paleontological field and lab techniques. PMID:20667597

Brinkman, Paul D

2010-09-01

280

Team of Paleontologists Discovers New Dinosaur Species  

NSDL National Science Digital Library

Working as part of a joint expedition, scientists from India and the United States (including the well-known paleontologist Paul Sereno from the University of Chicago) announced this Wednesday that they discovered a new carnivorous dinosaur species in the Narmada River region in western India. Based on the bones located by the team, this newly discovered species of dinosaur was between 25-30 feet long, had a horn above its skull, and was relatively heavy. As part of a collaborative effort with Jeff Wilson of the University of Michigan, Sereno reconstructed the dinosaur skull and presented a model to their Indian colleagues at Punjab University. It is believed that the new species (named Rajasaurus narmadensis) roamed the Southern Hemisphere land masses that constitute modern-day Madagascar, Africa, and South America. Utilizing these new findings, scientists hope to shed additional light on the potential cause of the dinosaurs' extinction, a subject that is often debated within the community of paleontologists.The first link leads to a news article about this recent find from Newind.com. The second link will take visitors to another news article from the Chicago Sun-Times that talks about Sereno's latest find. The third link leads to Paul Sereno's personal Web site from the University of Chicago, and contains interesting information about his numerous expeditions and his various experiences as an educator and scientist. The fourth link leads to the Project Exploration Web site, an organization founded by Sereno and his wife, Gabrielle Lyon, that is dedicated to making science "accessible to the public-with a special focus on city kids and girls." Here visitors can learn about the groups' many outreach programs, along with reading about events sponsored by the organization. The fifth link leads to a fabulous Web site provided by the BBC geared towards young people that features fact files on dinosaurs, a detailed chronology of their time on Earth, and several interactive games. The sixth and final link leads to a brief piece from Scientific American.com that talks a bit about the controversy surrounding the cause of the mass extinction of dinosaurs approximately 65 million years ago.

Grinnell, Max

281

Skull Ecomorphology of Megaherbivorous Dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta, Canada  

PubMed Central

Megaherbivorous dinosaur coexistence on the Late Cretaceous island continent of Laramidia has long puzzled researchers, owing to the mystery of how so many large herbivores (6–8 sympatric species, in many instances) could coexist on such a small (4–7 million km2) landmass. Various explanations have been put forth, one of which–dietary niche partitioning–forms the focus of this study. Here, we apply traditional morphometric methods to the skulls of megaherbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta to infer the ecomorphology of these animals and to test the niche partitioning hypothesis. We find evidence for niche partitioning not only among contemporaneous ankylosaurs, ceratopsids, and hadrosaurids, but also within these clades at the family and subfamily levels. Consubfamilial ceratopsids and hadrosaurids differ insignificantly in their inferred ecomorphologies, which may explain why they rarely overlap stratigraphically: interspecific competition prevented their coexistence. PMID:23874409

Mallon, Jordan C.; Anderson, Jason S.

2013-01-01

282

Should Dinosaurs be "Cloned" from Ancient DNA?  

NSDL National Science Digital Library

These are the teaching notes for a case study in which students use cooperative learning and role-playing to explore the scientific, technical, environmental, and ethical issues related to the possibility of cloning dinosaurs from ancient DNA. The case was designed to enhance the learning environment in an introductory class through cooperative problem-solving and to promote active participation in learning by using library and web resources to do research on a controversial topic in science and ethics. As the students pursue this case, they will apply knowledge explored in readings, lectures, and in-class discussions about dinosaurs, gain a general understanding of the revolutionary techniques used to discover and retrieve ancient DNA and to produce a clone, and improve communication and collaboration skills by working cooperatively in small groups and arguing a position in an authoritative fashion.

Soja, Constance; Huerta, Deborah

283

Paleoenvironment, paleoecology, and evolution of Maniraptoran "dinosaurs"  

E-print Network

by Newtonian Physics demonstrating there was truly a physical barrier preventing a running takeoff (Long et al., 2003). Burgers and Chiappe (1999) countered with a postulate that Archaeopteryx, using the wings as a primary thrust generator, could overcome... it was a highly developed, birdlike predator with an advanced brain and well-coordinated skeletal system. The holotype of Bambiraptor represents a small, sub-adult theropod dinosaur less 16 than one meter long and weighing approximately two kilograms...

Burnham, David A.

2007-05-01

284

Cockroaches Probably Cleaned Up after Dinosaurs  

PubMed Central

Dinosaurs undoubtedly produced huge quantities of excrements. But who cleaned up after them? Dung beetles and flies with rapid development were rare during most of the Mesozoic. Candidates for these duties are extinct cockroaches (Blattulidae), whose temporal range is associated with herbivorous dinosaurs. An opportunity to test this hypothesis arises from coprolites to some extent extruded from an immature cockroach preserved in the amber of Lebanon, studied using synchrotron X-ray microtomography. 1.06% of their volume is filled by particles of wood with smooth edges, in which size distribution directly supports their external pre-digestion. Because fungal pre-processing can be excluded based on the presence of large particles (combined with small total amount of wood) and absence of damages on wood, the likely source of wood are herbivore feces. Smaller particles were broken down biochemically in the cockroach hind gut, which indicates that the recent lignin-decomposing termite and cockroach endosymbionts might have been transferred to the cockroach gut upon feeding on dinosaur feces. PMID:24324610

Vrsansky, Peter; van de Kamp, Thomas; Azar, Dany; Prokin, Alexander; Vidlicka, L'ubomir; Vagovic, Patrik

2013-01-01

285

Dinosaur Peptides Suggest Mechanisms of Protein Survival  

SciTech Connect

Eleven collagen peptide sequences recovered from chemical extracts of dinosaur bones were mapped onto molecular models of the vertebrate collagen fibril derived from extant taxa. The dinosaur peptides localized to fibril regions protected by the close packing of collagen molecules, and contained few acidic amino acids. Four peptides mapped to collagen regions crucial for cell-collagen interactions and tissue development. Dinosaur peptides were not represented in more exposed parts of the collagen fibril or regions mediating intermolecular cross-linking. Thus functionally significant regions of collagen fibrils that are physically shielded within the fibril may be preferentially preserved in fossils. These results show empirically that structure-function relationships at the molecular level could contribute to selective preservation in fossilized vertebrate remains across geological time, suggest a 'preservation motif', and bolster current concepts linking collagen structure to biological function. This non-random distribution supports the hypothesis that the peptides are produced by the extinct organisms and suggests a chemical mechanism for survival.

San Antonio, James D.; Schweitzer, Mary H.; Jensen, Shane T.; Kalluri, Raghu; Buckley, Michael; Orgel, Joseph P.R.O. (Harvard-Med); (IIT); (NCSU); (UPENN); (Manchester); (Orthovita)

2011-09-16

286

Myocardial Lineage Development  

PubMed Central

The myocardium of the heart is composed of multiple highly specialized myocardial lineages, including those of the ventricular and atrial myocardium, and the specialized conduction system. Specification and maturation of each of these lineages during heart development is a highly ordered, ongoing process involving multiple signaling pathways and their intersection with transcriptional regulatory networks. Here, we attempt to summarize and compare much of what we know about specification and maturation of myocardial lineages from studies in several different vertebrate model systems. To date, most research has focused on early specification, and while there is still more to learn, less is known about factors that promote subsequent maturation of myocardial lineages required to build the functioning adult heart. PMID:21148449

Evans, Sylvia M.; Yelon, Deborah; Conlon, Frank L.; Kirby, Margaret L.

2010-01-01

287

"Dinosaurs." Kindergarten. Anchorage School District Elementary Science Program.  

ERIC Educational Resources Information Center

This unit contains 15 lessons on dinosaurs for kindergarten children. It provides a materials list, supplementary materials list, use of process skill terminology, unit objectives, vocabulary, six major dinosaurs, and background information. Lessons are: (1) "Webbing"; (2) "Introduction to the Big Six"; (3) "Paleontology and Fossils"; (4) "How Big…

Herminghaus, Trisha, Ed.

288

There Could Be a Dinosaur in Your Life!  

ERIC Educational Resources Information Center

This booklet describes how to make large two-dimensional models of dinosaur skeletons which can be effective teaching tools. Small laminated wood dinosaur models are enlarged, traced, and transferred to tri-wall cardboard (one-half inch thick) and cut out with a saber saw. Parts are then slotted and numbered for easy assembly. The result is a kit…

Jacob, Beth; Dempsey, Bill

289

GEOL 104 Dinosaurs: A Natural History Video Assignment  

E-print Network

, you are asked to watch the documentary series Walking With Dinosaurs (WWD). The version you will see the edited version shown on The Discovery Channel. There are six episodes in the series, each about thirty, that this is actual footage from the world of the dinosaurs, spliced together into TV shows just as might be done

Holtz Jr., Thomas R.

290

Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds  

E-print Network

) feathers and integumentary fila- ments are preserved in birds3­5 and non-avian theropod dinosaurs6 in integumentary filaments of non-avian dinosaurs, thus refuting recent claims13­16 that the filaments and Yixianosaurus11 . Integumentary filaments occur both in non-avian theropods that possessed true pennaceous

Benton, Michael

291

Dino-Facts: A Unit on Dinosaur Behavior  

NSDL National Science Digital Library

This activity takes students to the Bozeman, Montana area, where many dinosaurs once lived. They will gain an understanding of paleontological field work by analyzing evidence, developing hypotheses about dinosaur behavior, and supporting their hypotheses with evidence. This lesson contains materials needed, procedure, and extension ideas.

Scotchmoor, Judith

292

Dinosaur Fossils Predict Body Temperatures James F. Gillooly1*  

E-print Network

of America Perhaps the greatest mystery surrounding dinosaurs concerns whether they were endotherms]. Some have argued that dinosaurs were endotherms with body temper- atures that were high, relatively extant ectotherms and endotherms, and by predictions from biophysical models [5,6]. Resolution

Allen, Andrew P.

293

The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania.  

PubMed

The rise of dinosaurs was a major event in vertebrate history, but the timing of the origin and early diversification of the group remain poorly constrained. Here, we describe Nyasasaurus parringtoni gen. et sp. nov., which is identified as either the earliest known member of, or the sister-taxon to, Dinosauria. Nyasasaurus possesses a unique combination of dinosaur character states and an elevated growth rate similar to that of definitive early dinosaurs. It demonstrates that the initial dinosaur radiation occurred over a longer timescale than previously thought (possibly 15 Myr earlier), and that dinosaurs and their immediate relatives are better understood as part of a larger Middle Triassic archosauriform radiation. The African provenance of Nyasasaurus supports a southern Pangaean origin for Dinosauria. PMID:23221875

Nesbitt, Sterling J; Barrett, Paul M; Werning, Sarah; Sidor, Christian A; Charig, Alan J

2013-02-23

294

Systematic Palaeontology \\/ Paléontologie systématique (Vertebrate Palaeontology \\/ Paléontologie des Vertébrés) Dinosaurs of Portugal Dinosaures du Portugal  

Microsoft Academic Search

A synthesis on the state of art on dinosaur knowledge in Portugal is presented. The following genera have been recognized: Ceratosaurus, Torvosaurus , Lourinhanosaurus, Allosaurus, cf. Compsognathus, Stokesosaurus , cf. Richardoestesia, cf. Archaeopteryx, Euronychodon,cf. Paronychodon, Dinheirosaurus, Lourinhasaurus, Lusotitan, cf. Pleurocoelus, Lusitanosau- rus, Dacentrurus, Dracopelta, Phyllodon, Hypsilophodon , Alocodon, Trimucrodon, Draconyx, Iguanodon , and Taveirosaurus. Most are from Late Jurassic localities

Miguel Telles Antunes; Octávio Mateus

295

Stem cell differentiation: Sticky mechanical memory  

NASA Astrophysics Data System (ADS)

Physical cues from the extracellular environment influence the lineage commitment of stem cells. Now, experiments on human mesenchymal stem cells cultured on photodegradable hydrogels show that the cells' fate can also be determined by past physical environments.

Eyckmans, Jeroen; Chen, Christopher S.

2014-06-01

296

Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs  

PubMed Central

Convergent morphologies are thought to indicate functional similarity, arising because of a limited number of evolutionary or developmental pathways. Extant taxa displaying convergent morphologies are used as analogues to assess function in extinct taxa with similar characteristics. However, functional studies of extant taxa have shown that functional similarity can arise from differing morphologies, calling into question the paradigm that form and function are closely related. We test the hypothesis that convergent skeletal morphology indicates functional similarity in the fossil record using ornithischian dinosaurs. The rare transition from bipedality to quadrupedality occurred at least three times independently in this clade, resulting in a suite of convergent osteological characteristics. We use homology rather than analogy to provide an independent line of evidence about function, reconstructing soft tissues using the extant phylogenetic bracket and applying biomechanical concepts to produce qualitative assessments of muscle leverage. We also optimize character changes to investigate the sequence of character acquisition. Different lineages of quadrupedal ornithischian dinosaur stood and walked differently from each other, falsifying the hypothesis that osteological convergence indicates functional similarity. The acquisition of features correlated with quadrupedalism generally occurs in the same order in each clade, suggesting underlying developmental mechanisms that act as evolutionary constraints. PMID:22719033

Maidment, Susannah C. R.; Barrett, Paul M.

2012-01-01

297

A New Saurolophine Dinosaur from the Latest Cretaceous of Far Eastern Russia  

PubMed Central

Background Four main dinosaur sites have been investigated in latest Cretaceous deposits from the Amur/Heilongjiang Region: Jiayin and Wulaga in China (Yuliangze Formation), Blagoveschensk and Kundur in Russia (Udurchukan Formation). More than 90% of the bones discovered in these localities belong to hollow-crested lambeosaurine saurolophids, but flat-headed saurolophines are also represented: Kerberosaurus manakini at Blagoveschensk and Wulagasaurus dongi at Wulaga. Methodology/Principal Findings Herein we describe a new saurolophine dinosaur, Kundurosaurus nagornyi gen. et sp. nov., from the Udurchukan Formation (Maastrichtian) of Kundur, represented by disarticulated cranial and postcranial material. This new taxon is diagnosed by four autapomorphies. Conclusions/Significance A phylogenetic analysis of saurolophines indicates that Kundurosaurus nagornyi is nested within a rather robust clade including Edmontosaurus spp., Saurolophus spp., and Prosaurolophus maximus, possibly as a sister-taxon for Kerberosaurus manakini also from the Udurchukan Formation of Far Eastern Russia. The high diversity and mosaic distribution of Maastrichtian hadrosaurid faunas in the Amur-Heilongjiang region are the result of a complex palaeogeographical history and imply that many independent hadrosaurid lineages dispersed without any problem between western America and eastern Asia at the end of the Cretaceous. PMID:22666331

Godefroit, Pascal; Bolotsky, Yuri L.; Lauters, Pascaline

2012-01-01

298

From dinosaurs to modern bird diversity: extending the time scale of adaptive radiation.  

PubMed

What explains why some groups of organisms, like birds, are so species rich? And what explains their extraordinary ecological diversity, ranging from large, flightless birds to small migratory species that fly thousand of kilometers every year? These and similar questions have spurred great interest in adaptive radiation, the diversification of ecological traits in a rapidly speciating group of organisms. Although the initial formulation of modern concepts of adaptive radiation arose from consideration of the fossil record, rigorous attempts to identify adaptive radiation in the fossil record are still uncommon. Moreover, most studies of adaptive radiation concern groups that are less than 50 million years old. Thus, it is unclear how important adaptive radiation is over temporal scales that span much larger portions of the history of life. In this issue, Benson et al. test the idea of a "deep-time" adaptive radiation in dinosaurs, compiling and using one of the most comprehensive phylogenetic and body-size datasets for fossils. Using recent phylogenetic statistical methods, they find that in most clades of dinosaurs there is a strong signal of an "early burst" in body-size evolution, a predicted pattern of adaptive radiation in which rapid trait evolution happens early in a group's history and then slows down. They also find that body-size evolution did not slow down in the lineage leading to birds, hinting at why birds survived to the present day and diversified. This paper represents one of the most convincing attempts at understanding deep-time adaptive radiations. PMID:24802950

Moen, Daniel; Morlon, Hélène

2014-05-01

299

A late-surviving basal theropod dinosaur from the latest Triassic of North America  

PubMed Central

The oldest theropod dinosaurs are known from the Carnian of Argentina and Brazil. However, the evolutionary diversification of this group after its initial radiation but prior to the Triassic–Jurassic boundary is still poorly understood because of a sparse fossil record near that boundary. Here, we report on a new basal theropod, Daemonosaurus chauliodus gen. et sp. nov., from the latest Triassic ‘siltstone member’ of the Chinle Formation of the Coelophysis Quarry at Ghost Ranch, New Mexico. Based on a comprehensive phylogenetic analysis, Daemonosaurus is more closely related to coeval neotheropods (e.g. Coelophysis bauri) than to Herrerasauridae and Eoraptor. The skeletal structure of Daemonosaurus and the recently discovered Tawa bridge a morphological gap between Eoraptor and Herrerasauridae on one hand and neotheropods on the other, providing additional support for the theropod affinities of both Eoraptor and Herrerasauridae and demonstrating that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic. Various features of the skull of Daemonosaurus, including the procumbent dentary and premaxillary teeth and greatly enlarged premaxillary and anterior maxillary teeth, clearly set this taxon apart from coeval neotheropods and demonstrate unexpected disparity in cranial shape among theropod dinosaurs just prior to the end of the Triassic. PMID:21490016

Sues, Hans-Dieter; Nesbitt, Sterling J.; Berman, David S; Henrici, Amy C.

2011-01-01

300

A late-surviving basal theropod dinosaur from the latest Triassic of North America.  

PubMed

The oldest theropod dinosaurs are known from the Carnian of Argentina and Brazil. However, the evolutionary diversification of this group after its initial radiation but prior to the Triassic-Jurassic boundary is still poorly understood because of a sparse fossil record near that boundary. Here, we report on a new basal theropod, Daemonosaurus chauliodus gen. et sp. nov., from the latest Triassic 'siltstone member' of the Chinle Formation of the Coelophysis Quarry at Ghost Ranch, New Mexico. Based on a comprehensive phylogenetic analysis, Daemonosaurus is more closely related to coeval neotheropods (e.g. Coelophysis bauri) than to Herrerasauridae and Eoraptor. The skeletal structure of Daemonosaurus and the recently discovered Tawa bridge a morphological gap between Eoraptor and Herrerasauridae on one hand and neotheropods on the other, providing additional support for the theropod affinities of both Eoraptor and Herrerasauridae and demonstrating that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic. Various features of the skull of Daemonosaurus, including the procumbent dentary and premaxillary teeth and greatly enlarged premaxillary and anterior maxillary teeth, clearly set this taxon apart from coeval neotheropods and demonstrate unexpected disparity in cranial shape among theropod dinosaurs just prior to the end of the Triassic. PMID:21490016

Sues, Hans-Dieter; Nesbitt, Sterling J; Berman, David S; Henrici, Amy C

2011-11-22

301

Dinosaur Breath - Learning about the Carbon Cycle  

NSDL National Science Digital Library

This activity illustrates the carbon cycle using an age-appropriate hook, and it includes thorough discussion and hands-on experimentation. Students learn about the geological (ancient) carbon cycle; they investigate the role of dinosaurs in the carbon cycle, and the eventual storage of carbon in the form of chalk. Students discover how the carbon cycle has been occurring for millions of years and is necessary for life on Earth. Finally, they may extend their knowledge to the concept of global warming and how engineers are working to understand the carbon cycle and reduce harmful carbon dioxide emissions.

Cooper, Lauren; Zarske, Malinda S.; Yowell, Janet; Teachengineering - Integrated Teaching And Learning Program, Cu B.

302

Avian-like breathing mechanics in maniraptoran dinosaurs.  

PubMed

In 1868 Thomas Huxley first proposed that dinosaurs were the direct ancestors of birds and subsequent analyses have identified a suite of 'avian' characteristics in theropod dinosaurs. Ossified uncinate processes are found in most species of extant birds and also occur in extinct non-avian maniraptoran dinosaurs. Their presence in these dinosaurs represents another morphological character linking them to Aves, and further supports the presence of an avian-like air-sac respiratory system in theropod dinosaurs, prior to the evolution of flight. Here we report a phylogenetic analysis of the presence of uncinate processes in Aves and non-avian maniraptoran dinosaurs indicating that these were homologous structures. Furthermore, recent work on Canada geese has demonstrated that uncinate processes are integral to the mechanics of avian ventilation, facilitating both inspiration and expiration. In extant birds, uncinate processes function to increase the mechanical advantage for movements of the ribs and sternum during respiration. Our study presents a mechanism whereby uncinate processes, in conjunction with lateral and ventral movements of the sternum and gastral basket, affected avian-like breathing mechanics in extinct non-avian maniraptoran dinosaurs. PMID:17986432

Codd, Jonathan R; Manning, Phillip L; Norell, Mark A; Perry, Steven F

2008-01-22

303

Avian-like breathing mechanics in maniraptoran dinosaurs  

PubMed Central

In 1868 Thomas Huxley first proposed that dinosaurs were the direct ancestors of birds and subsequent analyses have identified a suite of ‘avian’ characteristics in theropod dinosaurs. Ossified uncinate processes are found in most species of extant birds and also occur in extinct non-avian maniraptoran dinosaurs. Their presence in these dinosaurs represents another morphological character linking them to Aves, and further supports the presence of an avian-like air-sac respiratory system in theropod dinosaurs, prior to the evolution of flight. Here we report a phylogenetic analysis of the presence of uncinate processes in Aves and non-avian maniraptoran dinosaurs indicating that these were homologous structures. Furthermore, recent work on Canada geese has demonstrated that uncinate processes are integral to the mechanics of avian ventilation, facilitating both inspiration and expiration. In extant birds, uncinate processes function to increase the mechanical advantage for movements of the ribs and sternum during respiration. Our study presents a mechanism whereby uncinate processes, in conjunction with lateral and ventral movements of the sternum and gastral basket, affected avian-like breathing mechanics in extinct non-avian maniraptoran dinosaurs. PMID:17986432

Codd, Jonathan R; Manning, Phillip L; Norell, Mark A; Perry, Steven F

2007-01-01

304

A palaeoequatorial ornithischian and new constraints on early dinosaur diversification.  

PubMed

Current characterizations of early dinosaur evolution are incomplete: existing palaeobiological and phylogenetic scenarios are based on a fossil record dominated by saurischians and the implications of the early ornithischian record are often overlooked. Moreover, the timings of deep phylogenetic divergences within Dinosauria are poorly constrained owing to the absence of a rigorous chronostratigraphical framework for key Late Triassic-Early Jurassic localities. A new dinosaur from the earliest Jurassic of the Venezuelan Andes is the first basal ornithischian recovered from terrestrial deposits directly associated with a precise radioisotopic date and the first-named dinosaur from northern South America. It expands the early palaeogeographical range of Ornithischia to palaeoequatorial regions, an area sometimes thought to be devoid of early dinosaur taxa, and offers insights into early dinosaur growth rates, the evolution of sociality and the rapid tempo of the global dinosaur radiation following the end-Triassic mass extinction, helping to underscore the importance of the ornithischian record in broad-scale discussions of early dinosaur history. PMID:25100698

Barrett, Paul M; Butler, Richard J; Mundil, Roland; Scheyer, Torsten M; Irmis, Randall B; Sánchez-Villagra, Marcelo R

2014-09-22

305

Hadrosaurus foulkii: Finding the World's First Dinosaur Skeleton  

NSDL National Science Digital Library

This site describes the discovery of a nearly-complete dinosaur skeleton, which occurred in 1858 in Haddonfield, New Jersey. There is information about what the Hadrosaurus dinosaur and its life was like and how the Haddonfield discovery led to the Bone Wars. The history of public displays of the skeleton as well as changes that were made in its stance and the shape of its skull based on new knowledge is explained. The site describes what the ravine where the first dinosaur bones were found is like today and how the fossil site was re-established and dedicated.

Levins, Hoag

306

Kinematics from a 163 Million-Year-Old Dinosaur Trackway  

NASA Astrophysics Data System (ADS)

Dinosaurs always grab the interest of students. Information about dinosaur locomotion is accessible from the trackways they left. In a unique connection to kinematics, evidence of the acceleration of a meat-eating dinosaur (theropod) is evident in Trackway 13 in Ardley Quarry in Oxfordshire, UK. This particular trackway is described by J.J. Day, D.B. Norman, P. Upchuch and H.P. Powell in Vol. 415 of Nature on pages 494 and 495, published in 2002. This particular theropod underwent an acceleration of about g/3. This example provides a fun and engaging exercise for students studying kinematics.

Lee, Scott

2011-10-01

307

Last updated 1/13/12 Genus List for Holtz (2007) Dinosaurs 1 * New genus; ** New grouping; ^ New genus name for previously unnamed dinosaur  

E-print Network

Last updated 1/13/12 Genus List for Holtz (2007) Dinosaurs 1 * New genus; ** New grouping; ^ New genus name for previously unnamed dinosaur Primitive Dinosauromorphs--Dinosaurs' Closest Relatives in the rock where its bones had dissolved away: a sort of "negative fossil." Scleromochlus hard fulcrum Late

Holtz Jr., Thomas R.

308

EMBRYONIC STEM CELLS/INDUCED PLURIPOTENT STEM CELLS Nanog Regulates Proliferation During Early Fish Development  

E-print Network

in the neuronal lineage of established OE: neural stem cells, which express the transcription factor Sox2; Mash1, Neurogenesis, Olfactory epithelium, Nasal cavity, Stem cell, Apoptosis, Cre recombinase, Fgf8, Foxg1, Sox2, Pax

DeSalle, Rob

309

Beyond T. rex: A Dinosaur Cladogram (title provided or enhanced by cataloger)  

NSDL National Science Digital Library

Students will have the chance to see some strange and unusual dinosaurs they have never heard of when they can play with the cladogram. A cladogram is like a family tree. It's a way of organizing dinosaurs based on the unique characteristics they share, like a three-toed foot or a hole in the hip socket. In order to see the information the student will roll over a dinosaur's name to see its picture, click the dinosaur name and roll over a blue dot to discover how dinosaurs on a branch of this tree are related and what physical characteristics they share. Nineteen dinosaurs are featured.

310

Launching the T-Lineage Developmental Programme  

PubMed Central

Preface Multipotent blood progenitor cells enter the thymus and begin a protracted differentiation process in which they gradually acquire T-cell characteristics while shedding their legacy of developmental plasticity. Notch signalling and basic helix-loop-helix E-protein transcription factors collaborate repeatedly to trigger and sustain this process throughout the period leading up to T-cell lineage commitment. Nevertheless, the process is discontinuous with separately regulated steps that demand roles for additional collaborating factors. This review discusses new evidence on the coordination of specification and commitment in the early T-cell pathway; effects of microenvironmental signals; the inheritance of stem-cell regulatory factors; and the ensemble of transcription factors that modulate the effects of Notch and E proteins, to distinguish individual stages and to polarize T-lineage fate determination. PMID:18097446

Rothenberg, Ellen V.; Moore, Jonathan E.; Yui, Mary A.

2011-01-01

311

Dinosaur Paleoecology: Determining the Diet of Ancient Animals  

NSDL National Science Digital Library

In this activity student groups, after being given the proper background information, will work together to determine the likely food source and overall body shape for each animal from a single dinosaur tooth. Class discussion will then be initiated by naming the animal whose tooth was described, then showing color pictures of reconstructions of the dinosaur and its environment. Additional discussion will be centered on how each dinosaur was able to develop teeth so well suited to its particular lifestyle. This will lead to the students discovering the concept of adaptation and survival of the fittest. This activity also allows the topic of dinosaurs to be used to introduce basic topics of paleobiology such as predator/prey interactions, scientific methods of determining lifestyles of extinct animals, and processes of evolution.

Davies, David

312

A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago.  

PubMed

Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the tail, the new fossil is the best-preserved predatory, non-avian dinosaur in Europe. It possesses a suite of characters that support its identification as a basal coelurosaur. A cladistic analysis indicates that the new taxon is closer to maniraptorans than to tyrannosauroids, grouping it with taxa often considered to be compsognathids. Large portions of integument are preserved along its tail. The absence of feathers or feather-like structures in a fossil phylogenetically nested within feathered theropods indicates that the evolution of these integumentary structures might be more complex than previously thought. PMID:16541071

Göhlich, Ursula B; Chiappe, Luis M

2006-03-16

313

Meet the Ceratosauria: The "Horned Reptile" Theropod Dinosaurs  

NSDL National Science Digital Library

The Ceratosauria represent the earliest theropod dinosaurs and indeed may include the ancestor to all later theropods. This site discusses the overall morphology and then goes into more detail for three examples: Ceratosaurus nasicornis, Dilophosaurus wetherilli, and Segisaurus halli.

314

Dinosaurs in the Dark: Grades 2-3: Electronic Book  

NSDL National Science Digital Library

This informational text introduces students to the dinosaurs found near the polar regions and discusses the adaptations that allowed these dinosaurs to survive in a dark and cold environment. The text is written at a grade two through grade three reading level. This is an onscreen version that contains recorded narration allowing students to listen to the text as they read along. Highlighted vocabulary words have individually recorded definitions heard by clicking on the links.

Fries-Gaither, Jessica

315

Dinosaurs in the Dark: Grades K-1: Electronic Book  

NSDL National Science Digital Library

This informational text introduces students to the dinosaurs found near the polar regions and discusses the adaptations that allowed these dinosaurs to survive in a dark and cold environment. The text is written at a kindergarten through grade one reading level. This is an onscreen version that contains recorded narration allowing students to listen to the text as they read along. Highlighted vocabulary words have individually recorded definitions heard by clicking on the links.

Fries-Gaither, Jessica

316

Dinosaurs in the Dark: K-1: Illustrated Book  

NSDL National Science Digital Library

This informational text introduces students to the dinosaurs found near the polar regions and discusses the adaptations that allowed these dinosaurs to survive in a dark and cold environment. The text is written at a kindergarten through grade one reading level. This version is a full-color PDF that can be printed, cut and folded to form a book. Each book contains color photographs and illustrations.

Fries-Gaither, Jessica

317

Cell Lineage A D Chisholm  

E-print Network

Cell Lineage A D Chisholm Copyright Ã? 2001 Academic Press doi: 10.1006/rwgn.2001.0172 Chisholm, A D Department of Biology, University of California, Santa Cruz, CA 95060, USA The cell lineage of an organism is the pattern of cell divisions during its development. Cell lineages are described by following cell divisions

Chisholm, Andrew

318

Mesozoic dinosaurs from Brazil and their biogeographic implications.  

PubMed

The record of dinosaur body-fossils in the Brazilian Mesozoic is restricted to the Triassic of Rio Grande do Sul and Cretaceous of various parts of the country. This includes 21 named species, two of which were regarded as nomina dubia, and 19 consensually assigned to Dinosauria. Additional eight supraspecific taxa have been identified based on fragmentary specimens and numerous dinosaur footprints known in Brazil. In fact, most Brazilian specimens related to dinosaurs are composed of isolated teeth and vertebrae. Despite the increase of fieldwork during the last decade, there are still no dinosaur body-fossils of Jurassic age and the evidence of ornithischians in Brazil is very limited. Dinosaur faunas from this country are generally correlated with those from other parts of Gondwana throughout the Mesozoic. During the Late Triassic, there is a close correspondence to Argentina and other south-Pangaea areas. Mid-Cretaceous faunas of northeastern Brazil resemble those of coeval deposits of North Africa and Argentina. Southern hemisphere spinosaurids are restricted to Africa and Brazil, whereas abelisaurids are still unknown in the Early Cretaceous of the latter. Late Cretaceous dinosaur assemblages of south-central Brazil are endemic only to genus or, more conspicuously, to species level, sharing closely related taxa with Argentina, Madagascar, Indo-Pakistan and, to a lesser degree, continental Africa. PMID:21437375

Bittencourt, Jonathas S; Langer, Max C

2011-03-01

319

The first ceratopsian dinosaur from South Korea  

NASA Astrophysics Data System (ADS)

In 2008, a new basal neoceratopsian was discovered in the Tando beds (Albian) of Tando Basin in South Korea. It represents the first ceratopsian dinosaur in the Korean peninsula and is assigned to Koreaceratops hwaseongensis gen. et sp. nov. Autapomorphies of Koreaceratops include very tall neural spines over five times higher than the associated centra in the distal caudals, and a unique astragalus divided into two fossae by a prominent craniocaudal ridge on the proximal surface. A phylogenetic analysis indicates that Koreaceratops is positioned between Archaeoceratops and all more derived neoceratopsians, and the elongation of caudal neural spines was an important derived character in non-ceratopsid neoceratopsians. The very tall caudal neural spines in Koreaceratops, Montanoceratops, Udanoceratops, Protoceratops, and Bagaceratops appear to be homoplasious, suggesting an independent adaptation, possibly for swimming. Skeletal evidence suggests that obligate quadrupedalism occurred gradually in neoceratopsians progressing from bipedal through facultative quadrupedalism, to complete quadrupedalism in Coronosauria.

Lee, Yuong-Nam; Ryan, Michael J.; Kobayashi, Yoshitsugu

2011-01-01

320

Largest Dinosaur Ever Discovered Found in Oklahoma  

NSDL National Science Digital Library

Originally discovered in a remote corner of Oklahoma in 1994, the fossil of what may have been the largest creature to ever walk the earth has been excavated by a research team from the University of Oklahoma. Dubbed Sauroposeidon proteles, or "thunder lizard," the dinosaur was almost 100 feet long, with a 39 foot neck and weighing over 50 tons, so big that it would have created minor seismic activity just by walking, according to scientists. The new find is about 110 million years old and consists of neck vertebrae, some almost five feet in length, together with neck ribs nearly twelve feet long. The find is also significant because it may shed light on the last of the North American sauropods, who died out about 100 million years ago. A paper on this new find is scheduled to appear in the Journal of Vertebrate Paleontology. The sites listed provide information and background material about this momentous discovery.

De Nie, Michael W.

321

Semiaquatic adaptations in a giant predatory dinosaur.  

PubMed

We describe adaptations for a semiaquatic lifestyle in the dinosaur Spinosaurus aegyptiacus. These adaptations include retraction of the fleshy nostrils to a position near the mid-region of the skull and an elongate neck and trunk that shift the center of body mass anterior to the knee joint. Unlike terrestrial theropods, the pelvic girdle is downsized, the hindlimbs are short, and all of the limb bones are solid without an open medullary cavity, for buoyancy control in water. The short, robust femur with hypertrophied flexor attachment and the low, flat-bottomed pedal claws are consistent with aquatic foot-propelled locomotion. Surface striations and bone microstructure suggest that the dorsal "sail" may have been enveloped in skin that functioned primarily for display on land and in water. PMID:25213375

Ibrahim, Nizar; Sereno, Paul C; Dal Sasso, Cristiano; Maganuco, Simone; Fabbri, Matteo; Martill, David M; Zouhri, Samir; Myhrvold, Nathan; Iurino, Dawid A

2014-09-26

322

Common Avian Infection Plagued the Tyrant Dinosaurs  

PubMed Central

Background Tyrannosaurus rex and other tyrannosaurid fossils often display multiple, smooth-edged full-thickness erosive lesions on the mandible, either unilaterally or bilaterally. The cause of these lesions in the Tyrannosaurus rex specimen FMNH PR2081 (known informally by the name ‘Sue’) has previously been attributed to actinomycosis, a bacterial bone infection, or bite wounds from other tyrannosaurids. Methodology/Principal Findings We conducted an extensive survey of tyrannosaurid specimens and identified ten individuals with full-thickness erosive lesions. These lesions were described, measured and photographed for comparison with one another. We also conducted an extensive survey of related archosaurs for similar lesions. We show here that these lesions are consistent with those caused by an avian parasitic infection called trichomonosis, which causes similar abnormalities on the mandible of modern birds, in particular raptors. Conclusions/Significance This finding represents the first evidence for the ancient evolutionary origin of an avian transmissible disease in non-avian theropod dinosaurs. It also provides a valuable insight into the palaeobiology of these now extinct animals. Based on the frequency with which these lesions occur, we hypothesize that tyrannosaurids were commonly infected by a Trichomonas gallinae-like protozoan. For tyrannosaurid populations, the only non-avian dinosaur group that show trichomonosis-type lesions, it is likely that the disease became endemic and spread as a result of antagonistic intraspecific behavior, consumption of prey infected by a Trichomonas gallinae-like protozoan and possibly even cannibalism. The severity of trichomonosis-related lesions in specimens such as Tyrannosaurus rex FMNH PR2081 and Tyrannosaurus rex MOR 980, strongly suggests that these animals died as a direct result of this disease, mostly likely through starvation. PMID:19789646

Wolff, Ewan D. S.; Salisbury, Steven W.; Horner, John R.; Varricchio, David J.

2009-01-01

323

Differentiation of human adipose stromal cells into hepatic lineage in vitro and in vivo  

Microsoft Academic Search

Embryonic stem cells (ES cells), bone marrow-derived mesenchymal stem cells, umbilical cord blood-derived mesenchymal stem cells, and hepatic stem cells in liver have been known as a useful source that can induce to differentiate into hepatocytes. In this study, we examined whether human adipose tissue-derived stromal cells (hADSC) can differentiate into hepatic lineage in vitro. hADSC, that were induced to

Min Jeong Seo; Su Young Suh; Yong Chan Bae; Jin Sup Jung

2005-01-01

324

A critical re?evaluation of the Late Triassic dinosaur taxa of North America  

Microsoft Academic Search

The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that Herrerasaurus and Eoraptor may not be theropods have forced a re?evaluation of saurischian and theropod synapomorphies. Here, we re?evaluate each purported Triassic dinosaur from North America on a specimen by specimen

Sterling J. Nesbitt; Randall B. Irmis; William G. Parker

2007-01-01

325

2006 Nature Publishing Group A new carnivorous dinosaur from the Late Jurassic  

E-print Network

© 2006 Nature Publishing Group A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago Ursula B. Go¨hlich1 & Luis M. Chiappe2 Small Late Jurassic theropod dinosaurs are rare worldwide,2 , neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic

Cai, Long

326

First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition  

NASA Astrophysics Data System (ADS)

Sauropod dinosaur bones are common in Mesozoic terrestrial sediments, but sauropod skulls are exceedingly rare—cranial materials are known for less than one third of sauropod genera and even fewer are known from complete skulls. Here we describe the first complete sauropod skull from the Cretaceous of the Americas, Abydosaurus mcintoshi, n. gen., n. sp., known from 104.46 ± 0.95 Ma (megannum) sediments from Dinosaur National Monument, USA. Abydosaurus shares close ancestry with Brachiosaurus, which appeared in the fossil record ca. 45 million years earlier and had substantially broader teeth. A survey of tooth shape in sauropodomorphs demonstrates that sauropods evolved broad crowns during the Early Jurassic but did not evolve narrow crowns until the Late Jurassic, when they occupied their greatest range of crown breadths. During the Cretaceous, brachiosaurids and other lineages independently underwent a marked diminution in tooth breadth, and before the latest Cretaceous broad-crowned sauropods were extinct on all continental landmasses. Differential survival and diversification of narrow-crowned sauropods in the Late Cretaceous appears to be a directed trend that was not correlated with changes in plant diversity or abundance, but may signal a shift towards elevated tooth replacement rates and high-wear dentition. Sauropods lacked many of the complex herbivorous adaptations present within contemporaneous ornithischian herbivores, such as beaks, cheeks, kinesis, and heterodonty. The spartan design of sauropod skulls may be related to their remarkably small size—sauropod skulls account for only 1/200th of total body volume compared to 1/30th body volume in ornithopod dinosaurs.

Chure, Daniel; Britt, Brooks B.; Whitlock, John A.; Wilson, Jeffrey A.

2010-04-01

327

Mountain Building Triggered Late Cretaceous North American Megaherbivore Dinosaur Radiation  

PubMed Central

Prior studies of Mesozoic biodiversity document a diversity peak for dinosaur species in the Campanian stage of the Late Cretaceous, yet have failed to provide explicit causal mechanisms. We provide evidence that a marked increase in North American dinosaur biodiversity can be attributed to dynamic orogenic episodes within the Western Interior Basin (WIB). Detailed fossil occurrences document an association between the shift from Sevier-style, latitudinally arrayed basins to smaller Laramide-style, longitudinally arrayed basins and a well substantiated decreased geographic range/increased taxonomic diversity of megaherbivorous dinosaur species. Dispersal-vicariance analysis demonstrates that the nearly identical biogeographic histories of the megaherbivorous dinosaur clades Ceratopsidae and Hadrosauridae are attributable to rapid diversification events within restricted basins and that isolation events are contemporaneous with known tectonic activity in the region. SymmeTREE analysis indicates that megaherbivorous dinosaur clades exhibited significant variation in diversification rates throughout the Late Cretaceous. Phylogenetic divergence estimates of fossil clades offer a new lower boundary on Laramide surficial deformation that precedes estimates based on sedimentological data alone. PMID:22876302

Gates, Terry A.; Prieto-Marquez, Albert; Zanno, Lindsay E.

2012-01-01

328

Career of the Month: An interview with Dinosaur Paleontologist Matthew Carrano  

NSDL National Science Digital Library

In the hunt for dinosaurs, only a small number of species have been unearthed. Many answers remain buried, awaiting discovery, which is why dinosaur paleontology today is such a thriving field. Dinosaur paleontologist Matthew Carrano not only works with real dinosaur bones every day, but he contributes to the centuries-old process of furthering scientific understanding. To Carrano, it's always exciting to uncover a new dinosaur fossil and be the first person in the history of the universe to see and touch it.

Sullivan, Megan

2006-11-01

329

Generalized Potential of Adult Neural Stem Cells  

Microsoft Academic Search

The differentiation potential of stem cells in tissues of the adult has been thought to be limited to cell lineages present in the organ from which they were derived, but there is evidence that some stem cells may have a broader differentiation repertoire. We show here that neural stem cells from the adult mouse brain can contribute to the formation

Diana L. Clarke; Clas B. Johansson; Johannes Wilbertz; Biborka Veress; Erik Nilsson; Helena Karlström; Urban Lendahl; Jonas Frisén

2000-01-01

330

Epidermal and dermal integumentary structures of ankylosaurian dinosaurs.  

PubMed

Ankylosaurian dinosaurs are most notable for their abundant and morphologically diverse osteoderms, which would have given them a spiky appearance in life. Isolated osteoderms are relatively common and provide important information about the structure of the ankylosaur dermis, but fossilized impressions of the soft-tissue epidermis of ankylosaurs are rare. Nevertheless, well-preserved integument exists on several ankylosaur fossils that shows osteoderms were covered by a single epidermal scale, but one or many millimeter-sized ossicles may be present under polygonal, basement epidermal scales. Evidence for the taxonomic utility of ankylosaurid epidermal scale architecture is presented for the first time. This study builds on previous osteological work that argues for a greater diversity of ankylosaurids in the Dinosaur Park Formation of Alberta than has been traditionally recognized and adds to the hypothesis that epidermal skin impressions are taxonomically relevant across diverse dinosaur clades. PMID:24105904

Arbour, Victoria M; Burns, Michael E; Bell, Phil R; Currie, Philip J

2014-01-01

331

Sauropod dinosaurs evolved moderately sized genomes unrelated to body size  

PubMed Central

Sauropodomorph dinosaurs include the largest land animals to have ever lived, some reaching up to 10 times the mass of an African elephant. Despite their status defining the upper range for body size in land animals, it remains unknown whether sauropodomorphs evolved larger-sized genomes than non-avian theropods, their sister taxon, or whether a relationship exists between genome size and body size in dinosaurs, two questions critical for understanding broad patterns of genome evolution in dinosaurs. Here we report inferences of genome size for 10 sauropodomorph taxa. The estimates are derived from a Bayesian phylogenetic generalized least squares approach that generates posterior distributions of regression models relating genome size to osteocyte lacunae volume in extant tetrapods. We estimate that the average genome size of sauropodomorphs was 2.02 pg (range of species means: 1.77–2.21 pg), a value in the upper range of extant birds (mean = 1.42 pg, range: 0.97–2.16 pg) and near the average for extant non-avian reptiles (mean = 2.24 pg, range: 1.05–5.44 pg). The results suggest that the variation in size and architecture of genomes in extinct dinosaurs was lower than the variation found in mammals. A substantial difference in genome size separates the two major clades within dinosaurs, Ornithischia (large genomes) and Saurischia (moderate to small genomes). We find no relationship between body size and estimated genome size in extinct dinosaurs, which suggests that neutral forces did not dominate the evolution of genome size in this group. PMID:19793755

Organ, Chris L.; Brusatte, Stephen L.; Stein, Koen

2009-01-01

332

Molecular preservation in Late Cretaceous sauropod dinosaur eggshells  

PubMed Central

Exceptionally preserved sauropod eggshells discovered in Upper Cretaceous (Campanian) deposits in Patagonia, Argentina, contain skeletal remains and soft tissues of embryonic Titanosaurid dinosaurs. To preserve these labile embryonic remains, the rate of mineral precipitation must have superseded post-mortem degradative processes, resulting in virtually instantaneous mineralization of soft tissues. If so, mineralization may also have been rapid enough to retain fragments of original biomolecules in these specimens. To investigate preservation of biomolecular compounds in these well-preserved sauropod dinosaur eggshells, we applied multiple analytical techniques. Results demonstrate organic compounds and antigenic structures similar to those found in extant eggshells. PMID:15888409

Schweitzer, M.H; Chiappe, L; Garrido, A.C; Lowenstein, J.M; Pincus, S.H

2005-01-01

333

Palaeoenvironmental controls on the distribution of Cretaceous herbivorous dinosaurs  

NASA Astrophysics Data System (ADS)

Previous attempts to determine palaeoenvironmental preferences in dinosaurs have generally been qualitative assessments based upon data from restricted geographical areas. Here, we use a global database of Cretaceous herbivorous dinosaurs to identify significant associations between clades and broad palaeoenvironmental categories (‘terrestrial’, ‘coastal’, ‘marine’). Nodosaurid ankylosaurs and hadrosaurids show significant positive associations with marine sediments, while marginocephalians (Ceratopsia, Pachycephalosauria), saurischians (herbivorous theropods, Sauropoda) and ankylosaurid ankylosaurs are significantly positively associated with terrestrial sediments. These results provide quantitative support for the hypothesis that some clades (Nodosauridae, Hadrosauridae) were more abundant in coastal and/or fluvial environments, while others (e.g. Marginocephalia, Ankylosauridae) preferentially inhabited more distal environments.

Butler, Richard J.; Barrett, Paul M.

2008-11-01

334

A pair of shelled eggs inside a female dinosaur.  

PubMed

An oviraptosaurian specimen (Dinosauria, Theropoda) from an Upper Cretaceous formation in China retains a pair of shelled eggs in the pelvis, providing direct evidence that oviraptorosaurian dinosaurs laid paired elongatoolithid eggs. The presence of the paired eggs suggests that theropod dinosaurs had two functional oviducts (like crocodiles) but that each oviduct produced only one egg at a time and that an entire egg clutch was laid through multiple ovipositions (like birds). The orientations of the eggs inside the skeleton and in clutches indicate that the mother came to the center of the nest to lay eggs. PMID:15831749

Sato, Tamaki; Cheng, Yen-nien; Wu, Xiao-chun; Zelenitsky, Darla K; Hsiao, Yu-fu

2005-04-15

335

Dinosaur Tracksites of the Paluxy River Valley ( Glen Rose Formation , Lower Cretaceous ), Dinosaur Valley State Park , Somervell County , Texas Rastros de dinosaurios del valle del r'io Paluxy ( Formaci'on Glen Rose , Cret'acico Inferior ), Dinosaur Valley  

Microsoft Academic Search

In 1940 R.T. Bird of the American Museum of Natural History collected segments of a sauropod and a theropod trackway from a site in the bed (Glen Rose Formation; Lower Cretaceous) of the Paluxy River, in what is now Dinosaur Valley State Park (Glen Rose, Texas, USA). However, Bird left undocumented thousands of other dinosaur footprints from this and other

James O Farlow; Mike O'Brien; G J Kuban; B F Dattilo; Karl T. Bates; Peter L. Falkingham; L. Piñuela; A. Rose; A. Freels; C. Kumagai; C. Libben; J. Smith; J. Whitcraft

2012-01-01

336

Structural Extremes in a Cretaceous Dinosaur  

PubMed Central

Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. We used high resolution computed tomography, stereolithography, and standard molding and casting techniques to reassemble the extremely fragile skull. Computed tomography also allowed us to render the first endocast for a sauropod preserving portions of the olfactory bulbs, cerebrum and inner ear, the latter permitting us to establish habitual head posture. To elucidate evidence of tooth wear and tooth replacement rate, we used photographic-casting techniques and crown thin sections, respectively. To reconstruct its 9-meter postcranial skeleton, we combined and size-adjusted multiple partial skeletons. Finally, we used maximum parsimony algorithms on character data to obtain the best estimate of phylogenetic relationships among diplodocoid sauropods. Nigersaurus taqueti shows extreme adaptations for a dinosaurian herbivore including a skull of extremely light construction, tooth batteries located at the distal end of the jaws, tooth replacement as fast as one per month, an expanded muzzle that faces directly toward the ground, and hollow presacral vertebral centra with more air sac space than bone by volume. A cranial endocast provides the first reasonably complete view of a sauropod brain including its small olfactory bulbs and cerebrum. Skeletal and dental evidence suggests that Nigersaurus was a ground-level herbivore that gathered and sliced relatively soft vegetation, the culmination of a low-browsing feeding strategy first established among diplodocoids during the Jurassic. PMID:18030355

Sereno, Paul C.; Wilson, Jeffrey A.; Witmer, Lawrence M.; Whitlock, John A.; Maga, Abdoulaye; Ide, Oumarou; Rowe, Timothy A.

2007-01-01

337

A revised taxonomy of the iguanodont dinosaur genera and species  

Microsoft Academic Search

Criteria for designating dinosaur genera are inconsistent; some very similar species are highly split at the generic level, other anatomically disparate species are united at the same rank. Since the mid-1800s the classic genus Iguanodon has become a taxonomic grab-bag containing species spanning most of the Early Cretaceous of the northern hemisphere. Recently the genus was radically redesignated when the

Gregory S. Paul

2008-01-01

338

Dinosaur Adventures and History of Life on Earth  

E-print Network

June 16­20 · Dinosaur Adventures and History of Life on Earth · Kitchen Cabinet Science · Mission, Servers and Beyond July 7­11 · It's A Bug's Life · EcoExplorers · Robotics (beginning) · Personal Genomics to Mars · Computer Programing with SCRATCH · Web Design June 23­27 · Infinity and Beyond · Summer

Schladow, S. Geoffrey

339

Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs  

Microsoft Academic Search

How evolutionary changes in body size are brought about by variance in developmental timing and\\/or growth rates (also known as heterochrony) is a topic of considerable interest in evolutionary biology. In particular, extreme size change leading to gigantism occurred within the dinosaurs on multiple occasions. Whether this change was brought about by accelerated growth, delayed maturity or a combination of

Gregory M. Erickson; Peter J. Makovicky; Philip J. Currie; Mark A. Norell; Scott A. Yerby; Christopher A. Brochu

2004-01-01

340

Hettangian (Early Jurassic) Dinosaur Tracksites from the Mecsek Mountains, Hungary  

Microsoft Academic Search

Isolated theropod dinosaur tracks were first collected in Hungary from Hettangian (Lower Jurassic) beds of the Mecsek Coal Formation in 1966 and described as Komlosaurus carbonisKordos, 1983. Our study is based on newly collected material from additional track-bearing beds. The description of the two largest preserved surfaces containing a total of 102 tracks that can be referred to as 21

Attila ?si; József Pálfy; László Makádi; Zoltán Szentesi; Péter Gulyás; Márton Rabi; Gábor Botfalvai; Kinga Hips

2011-01-01

341

INTEGRATED LIDAR & PHOTOGRAMMETRIC DOCUMENTATION OF THE RED GULCH DINOSAUR  

E-print Network

101 INTEGRATED LIDAR & PHOTOGRAMMETRIC DOCUMENTATION OF THE RED GULCH DINOSAUR TRACKSITE (WYOMING And Range (LiDAR) and photogrammetric survey at the RGDT carried out in the summer of 2008 (Figure 2). A fully integrated digital camera allows photographic images to be combined with LiDAR point clouds

Falkingham, Peter

342

A bizarre predatory dinosaur from the Late Cretaceous of Madagascar  

Microsoft Academic Search

Here we report the discovery of a small-bodied (~1.8 m) predatory dinosaur from the Late Cretaceous (Maastrichtian) of Madagascar. Masiakasaurus knopfleri, gen. et sp. nov., represented by several skull elements and much of the postcranial skeleton, is unique in being the only known theropod with a highly procumbent and distinctly heterodont lower dentition. Such a derived dental morphology is otherwise

Scott D. Sampson; Matthew T. Carrano; Catherine A. Forster

2001-01-01

343

An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures  

Microsoft Academic Search

Ornithischia is one of the two major groups of dinosaurs, with heterodontosauridae as one of its major clades. Heterodontosauridae is characterized by small, gracile bodies and a problematic phylogenetic position. Recent phylogenetic work indicates that it represents the most basal group of all well-known ornithischians. Previous heterodontosaurid records are mainly from the Early Jurassic period (205-190 million years ago) of

Xiao-Ting Zheng; Hai-Lu You; Xing Xu; Zhi-Ming Dong

2009-01-01

344

In vitro differentiation of embryonic stem cells  

Microsoft Academic Search

Under appropriate conditions in culture, embryonic stem cells with differentiate and form embryoid bodies that have been shown to contain cells of the hematopoietic, endothelial, muscle and neuronal lineages. Many aspects of the lineage-specific differentiation programs observed within the embryoid bodies reflect those found in the embryo, indicating that this model system provides access to early cell populations that develop

Gordon M Keller

1995-01-01

345

Expression of human cytokines dramatically improves reconstitution of specific human-blood lineage cells in humanized mice  

E-print Network

Adoptive transfer of human hematopoietic stem cells (HSCs) into mice lacking T, B and natural killer (NK) cells leads to development of human-blood lineage cells in the recipient mice (humanized mice). Although human B ...

Chen, Qingfeng

346

CRETACEOUS CLIMATE SENSITIVITY STUDY USING DINOSAUR & PLANT PALEOBIOGEOGRAPHY  

NASA Astrophysics Data System (ADS)

The Early Cretaceous was characterized by cool poles and moderate global temperatures (~16° C). During the mid and late Cretaceous, long-term global warming (~20° - 22° C) was driven by increasing levels of CO2, rising sea level (lowering albedo) and the continuing breakup of Pangea. Paleoclimatic reconstructions for four time intervals during the Cretaceous: Middle Campanian (80 Ma), Cenomanian/Turonian (90 Ma), Early Albian (110 Ma) and Barremian-Hauterivian (130Ma) are presented here. These paleoclimate simulations were prepared using the Fast Ocean and Atmosphere Model (FOAM). The simulated results show the pattern of the pole-to-Equator temperature gradients, rainfall, surface run-off, the location of major rivers and deltas. In order to investigate the effect of potential dispersal routes on paleobiogeographic patterns, a time-slice series of maps from Early - Late Cretaceous were produced showing plots of dinosaur and plant fossil distributions. These Maps were created utilizing: 1) plant fossil localities from the GEON and Paleobiology (PBDB) databases; and 2) dinosaur fossil localities from an updated version of the Dinosauria (Weishampel, 2004) database. These results are compared to two different types of datasets, 1) Paleotemperature database for the Cretaceous and 2) locality data obtained from GEON, PBDB and Dinosauria database. Global latitudinal mean temperatures from both the model and the paelotemperature database were plotted on a series of latitudinal graphs along with the distributions of fossil plants and dinosaurs. It was found that most dinosaur localities through the Cretaceous tend to cluster within specific climate belts, or envelopes. Also, these Cretaceous maps show variance in biogeographic zonation of both plants and dinosaurs that is commensurate with reconstructed climate patterns and geography. These data are particularly useful for understanding the response of late Mesozoic ecosystems to geographic and climatic conditions that differed markedly from the present. Studies of past biotas and their changes may elucidate the role of climatic and geographic factors in driving changes in species distributions, ecosystem organization, and evolutionary dynamics over time.

Goswami, A.; Main, D. J.; Noto, C. R.; Moore, T. L.; Scotese, C.

2009-12-01

347

Pathologic bone tissues in a Turkey vulture and a nonavian dinosaur: implications for interpreting endosteal bone and radial fibrolamellar bone in fossil dinosaurs.  

PubMed

We report on similar pathological bone microstructure in an extant turkey vulture (Cathartes aura) and a nonavian dinosaur from Transylvania. Both these individuals exhibit distinctive periosteal reactive bone deposition accompanied by endosteal bone deposits in the medullary cavity. Our findings have direct implications on the two novel bone tissues recently described among nonavian dinosaurs, radial fibrolamellar bone tissue and medullary bone tissue. On the basis of the observed morphology of the periosteal reactive bone in the turkey vulture and the Transylvanian dinosaur, we propose that the radial fibrolamellar bone tissues observed in mature dinosaurs may have had a pathological origin. Our analysis also shows that on the basis of origin, location, and morphology, pathologically derived endosteal bone tissue can be similar to medullary bone tissues described in nonavian dinosaurs. As such, we caution the interpretation of all endosteally derived bone tissue as homologous to avian medullary bone. PMID:19711479

Chinsamy, Anusuya; Tumarkin-Deratzian, Allison

2009-09-01

348

What drove reversions to quadrupedality in ornithischian dinosaurs? Testing hypotheses using centre of mass modelling.  

PubMed

The exceptionally rare transition to quadrupedalism from bipedal ancestors occurred on three independent occasions in ornithischian dinosaurs. The possible driving forces behind these transitions remain elusive, but several hypotheses-including the development of dermal armour and the expansion of head size and cranial ornamentation-have been proposed to account for this major shift in stance. We modelled the position of the centre of mass (CoM) in several exemplar ornithischian taxa and demonstrate that the anterior shifts in CoM position associated with the development of an enlarged skull ornamented with horns and frills for display/defence may have been one of the drivers promoting ceratopsian quadrupedality. A posterior shift in CoM position coincident with the development of extensive dermal armour in thyreophorans demonstrates this cannot have been a primary causative mechanism for quadrupedality in this clade. Quadrupedalism developed in response to different selective pressures in each ornithischian lineage, indicating different evolutionary pathways to convergent quadrupedal morphology. PMID:25228349

Maidment, Susannah C R; Henderson, Donald M; Barrett, Paul M

2014-11-01

349

No evidence for directional evolution of body mass in herbivorous theropod dinosaurs  

PubMed Central

The correlation between large body size and digestive efficiency has been hypothesized to have driven trends of increasing mass in herbivorous clades by means of directional selection. Yet, to date, few studies have investigated this relationship from a phylogenetic perspective, and none, to our knowledge, with regard to trophic shifts. Here, we reconstruct body mass in the three major subclades of non-avian theropod dinosaurs whose ecomorphology is correlated with extrinsic evidence of at least facultative herbivory in the fossil record—all of which also achieve relative gigantism (more than 3000 kg). Ordinary least-squares regressions on natural log-transformed mean mass recover significant correlations between increasing mass and geological time. However, tests for directional evolution in body mass find no support for a phylogenetic trend, instead favouring passive models of trait evolution. Cross-correlation of sympatric taxa from five localities in Asia reveals that environmental influences such as differential habitat sampling and/or taphonomic filtering affect the preserved record of dinosaurian body mass in the Cretaceous. Our results are congruent with studies documenting that behavioural and/or ecological factors may mitigate the benefit of increasing mass in extant taxa, and suggest that the hypothesis can be extrapolated to herbivorous lineages across geological time scales. PMID:23193135

Zanno, Lindsay E.; Makovicky, Peter J.

2013-01-01

350

Bird-like anatomy, posture, and behavior revealed by an early jurassic theropod dinosaur resting trace  

USGS Publications Warehouse

Background: Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb. Methodology/Principal Findings: Here we describe a well-preserved theropod trackway in a Lower Jurassic (???198 millionyear- old) lacustrine beach sandstone in the Whitmore Point Member of the Moenave Formation in southwestern Utah. The trackway consists of prints of typical morphology, intermittent tail drags and, unusually, traces made by the animal resting on the substrate in a posture very similar to modern birds. The resting trace includes symmetrical pes impressions and well-defined impressions made by both hands, the tail, and the ischial callosity. Conclusions/Significance: The manus impressions corroborate that early theropods, like later birds, held their palms facing medially, in contrast to manus prints previously attributed to theropods that have forward-pointing digits. Both the symmetrical resting posture and the medially-facing palms therefore evolved by the Early Jurassic, much earlier in the theropod lineage than previously recognized, and may characterize all theropods.

Milner, A. R. C.; Harris, J. D.; Lockley, M. G.; Kirkland, J. I.; Matthews, N. A.

2009-01-01

351

Rates of dinosaur limb evolution provide evidence for exceptional radiation in Mesozoic birds.  

PubMed

Birds are the most diverse living tetrapod group and are a model of large-scale adaptive radiation. Neontological studies suggest a radiation within the avian crown group, long after the origin of flight. However, deep time patterns of bird evolution remain obscure because only limited fossil data have been considered. We analyse cladogenesis and limb evolution on the entire tree of Mesozoic theropods, documenting the dinosaur-bird transition and immediate origins of powered flight. Mesozoic birds inherited constraints on forelimb evolution from non-flying ancestors, and species diversification rates did not accelerate in the earliest flying taxa. However, Early Cretaceous short-tailed birds exhibit both phenotypic release of the hindlimb and increased diversification rates, unparalleled in magnitude at any other time in the first 155 Myr of theropod evolution. Thus, a Cretaceous adaptive radiation of stem-group birds was enabled by restructuring of the terrestrial locomotor module, which represents a key innovation. Our results suggest two phases of radiation in Avialae: with the Cretaceous diversification overwritten by extinctions of stem-group birds at the Cretaceous-Palaeogene boundary, and subsequent diversification of the crown group. Our findings illustrate the importance of fossil data for understanding the macroevolutionary processes generating modern biodiversity. PMID:23945695

Benson, Roger B J; Choiniere, Jonah N

2013-10-01

352

Rates of dinosaur limb evolution provide evidence for exceptional radiation in Mesozoic birds  

PubMed Central

Birds are the most diverse living tetrapod group and are a model of large-scale adaptive radiation. Neontological studies suggest a radiation within the avian crown group, long after the origin of flight. However, deep time patterns of bird evolution remain obscure because only limited fossil data have been considered. We analyse cladogenesis and limb evolution on the entire tree of Mesozoic theropods, documenting the dinosaur–bird transition and immediate origins of powered flight. Mesozoic birds inherited constraints on forelimb evolution from non-flying ancestors, and species diversification rates did not accelerate in the earliest flying taxa. However, Early Cretaceous short-tailed birds exhibit both phenotypic release of the hindlimb and increased diversification rates, unparalleled in magnitude at any other time in the first 155 Myr of theropod evolution. Thus, a Cretaceous adaptive radiation of stem-group birds was enabled by restructuring of the terrestrial locomotor module, which represents a key innovation. Our results suggest two phases of radiation in Avialae: with the Cretaceous diversification overwritten by extinctions of stem-group birds at the Cretaceous–Palaeogene boundary, and subsequent diversification of the crown group. Our findings illustrate the importance of fossil data for understanding the macroevolutionary processes generating modern biodiversity. PMID:23945695

Benson, Roger B. J.; Choiniere, Jonah N.

2013-01-01

353

Irreversible fate commitment in the Arabidopsis stomatal lineage requires a FAMA and RETINOBLASTOMA-RELATED module.  

PubMed

The presumed totipotency of plant cells leads to questions about how specific stem cell lineages and terminal fates could be established. In the Arabidopsis stomatal lineage, a transient self-renewing phase creates precursors that differentiate into one of two epidermal cell types, guard cells or pavement cells. We found that irreversible differentiation of guard cells involves RETINOBLASTOMA-RELATED (RBR) recruitment to regulatory regions of master regulators of stomatal initiation, facilitated through interaction with a terminal stomatal lineage transcription factor, FAMA. Disrupting physical interactions between FAMA and RBR preferentially reveals the role of RBR in enforcing fate commitment over its role in cell-cycle control in this developmental context. Analysis of the phenotypes linked to the modulation of FAMA and RBR sheds new light on the way iterative divisions and terminal differentiation are coordinately regulated in a plant stem-cell lineage. PMID:25303364

Matos, Juliana L; Lau, On Sun; Hachez, Charles; Cruz-Ramírez, Alfredo; Scheres, Ben; Bergmann, Dominique C

2014-01-01

354

Irreversible fate commitment in the Arabidopsis stomatal lineage requires a FAMA and RETINOBLASTOMA-RELATED module  

PubMed Central

The presumed totipotency of plant cells leads to questions about how specific stem cell lineages and terminal fates could be established. In the Arabidopsis stomatal lineage, a transient self-renewing phase creates precursors that differentiate into one of two epidermal cell types, guard cells or pavement cells. We found that irreversible differentiation of guard cells involves RETINOBLASTOMA-RELATED (RBR) recruitment to regulatory regions of master regulators of stomatal initiation, facilitated through interaction with a terminal stomatal lineage transcription factor, FAMA. Disrupting physical interactions between FAMA and RBR preferentially reveals the role of RBR in enforcing fate commitment over its role in cell-cycle control in this developmental context. Analysis of the phenotypes linked to the modulation of FAMA and RBR sheds new light on the way iterative divisions and terminal differentiation are coordinately regulated in a plant stem-cell lineage. DOI: http://dx.doi.org/10.7554/eLife.03271.001 PMID:25303364

Matos, Juliana L; Lau, On Sun; Hachez, Charles; Cruz-Ramírez, Alfredo; Scheres, Ben; Bergmann, Dominique C

2014-01-01

355

Gradual dinosaur extinction and simultaneous ungulate radiation in the hell creek formation.  

PubMed

Dinosaur extinction in Montana, Alberta, and Wyoming was a gradual process that began 7 million years before the end of the Cretaceous and accelerated rapidly in the final 0.3 million years of the Cretaceous, during the interval of apparent competition from rapidly evolving immigrating ungulates. This interval involves rapid reduction in both diversity and population density of dinosaurs. The last dinosaurs known are from a channel that contains teeth of Mantuan mammals, seven species of dinosaurs, and Paleocene pollen. The top of this channel is 1.3 meters above the likely position of the iridium anomaly, the Cretaceous/Tertiary boundary. PMID:17781415

Sloan, R E; Rigby, J K; VAN Valen, L M; Gabriel, D

1986-05-01

356

K-Pg events facilitated lineage transitions between terrestrial and aquatic ecosystems.  

PubMed

We use dated phylogenetic trees for tetrapod vertebrates to identify lineages that shifted between terrestrial and aquatic ecosystems in terms of feeding or development, and to assess the timing of such events. Both stem and crown lineage ages indicate a peak in transition events in correspondence with the K-Pg mass extinction. This meets the prediction that changes in competitive pressure and resource availability following mass extinction events should facilitate such transitions. PMID:24919699

Proche?, Serban; Polgar, Gianluca; Marshall, David J

2014-06-01

357

The Earliest Thymic T Cell Progenitors Sustain B Cell and Myeloid Lineage Potentials  

PubMed Central

The stepwise commitment from hematopoietic stem cells in the bone marrow (BM) to T lymphocyte-restricted progenitors in the thymus represents a paradigm for understanding the requirement for distinct extrinsic cues during different stages of lineage restriction from multipotent to lineage restricted progenitors. However, the commitment stage at which progenitors migrate from the BM to the thymus remains unclear. Here we provide functional and molecular evidence at the single cell level that the earliest progenitors in the neonatal thymus possessed combined granulocyte-monocyte, T and B lymphocyte, but not megakaryocyte-erythroid lineage potential. These potentials were identical to those of thymus-seeding progenitors in the BM, which were closely related at the molecular level. These findings establish the distinct lineage-restriction stage at which the T lineage commitment transits from the BM to the remote thymus. PMID:22344248

Luc, Sidinh; Luis, Tiago C.; Boukarabila, Hanane; Macaulay, Iain C.; Buza-Vidas, Natalija; Bouriez-Jones, Tiphaine; Lutteropp, Michael; Woll, Petter S.; Loughran, Stephen J.; Mead, Adam J.; Hultquist, Anne; Brown, John; Mizukami, Takuo; Matsuoka, Sahoko; Ferry, Helen; Anderson, Kristina; Duarte, Sara; Atkinson, Deborah; Soneji, Shamit; Domanski, Aniela; Farley, Alison; Sanjuan-Pla, Alejandra; Carella, Cintia; Patient, Roger; de Bruijn, Marella; Enver, Tariq; Nerlov, Claus; Blackburn, Clare; Godin, Isabelle; Jacobsen, Sten Eirik W.

2012-01-01

358

STEM, STEM Education, STEMmania  

ERIC Educational Resources Information Center

In this article, the author introduces integrative STEM (science, technology, engineering, and/or mathematics) education and discusses the importance of the program. The notion of integrative STEM education includes approaches that explore teaching and learning between/among any two or more of the STEM subject areas, and/or between a STEM subject…

Sanders, Mark

2009-01-01

359

A gigantic feathered dinosaur from the lower cretaceous of China.  

PubMed

Numerous feathered dinosaur specimens have recently been recovered from the Middle-Upper Jurassic and Lower Cretaceous deposits of northeastern China, but most of them represent small animals. Here we report the discovery of a gigantic new basal tyrannosauroid, Yutyrannus huali gen. et sp. nov., based on three nearly complete skeletons representing two distinct ontogenetic stages from the Lower Cretaceous Yixian Formation of Liaoning Province, China. Y. huali shares some features, particularly of the cranium, with derived tyrannosauroids, but is similar to other basal tyrannosauroids in possessing a three-fingered manus and a typical theropod pes. Morphometric analysis suggests that Y. huali differed from tyrannosaurids in its growth strategy. Most significantly, Y. huali bears long filamentous feathers, thus providing direct evidence for the presence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution. PMID:22481363

Xu, Xing; Wang, Kebai; Zhang, Ke; Ma, Qingyu; Xing, Lida; Sullivan, Corwin; Hu, Dongyu; Cheng, Shuqing; Wang, Shuo

2012-04-01

360

A bizarre predatory dinosaur from the Late Cretaceous of Madagascar.  

PubMed

Here we report the discovery of a small-bodied (approximately 1.8 m) predatory dinosaur from the Late Cretaceous (Maastrichtian) of Madagascar. Masiakasaurus knopfleri, gen. et sp. nov., represented by several skull elements and much of the postcranial skeleton, is unique in being the only known theropod with a highly procumbent and distinctly heterodont lower dentition. Such a derived dental morphology is otherwise unknown among dinosaurs. Numerous skeletal characteristics indicate that Masiakasaurus is a member of Abelisauroidea, an enigmatic clade of Gondwanan theropods. Previously, small-bodied abelisauroids were known only from Argentina. The occurrence of Masiakasaurus on Madagascar suggests that small-bodied abelisauroids, like their larger-bodied counterparts, were more cosmopolitan, radiating throughout much of Gondwana and paralleling the diversification of small coelurosaur theropods in Laurasia. PMID:11206544

Sampson, S D; Carrano, M T; Forster, C A

2001-01-25

361

An Abelisauroid Theropod Dinosaur from the Turonian of Madagascar  

PubMed Central

Geophysical evidence strongly supports the complete isolation of India and Madagascar (Indo-Madagascar) by ?100 million years ago, though sparse terrestrial fossil records from these regions prior to ?70 million years ago have limited insights into their biogeographic history during the Cretaceous. A new theropod dinosaur, Dahalokely tokana, from Turonian-aged (?90 million years old) strata of northernmost Madagascar is represented by a partial axial column. Autapomorphies include a prominently convex prezygoepipophyseal lamina on cervical vertebrae and a divided infraprezygapophyseal fossa through the mid-dorsal region, among others. Phylogenetic analysis definitively recovers the species as an abelisauroid theropod and weakly as a noasaurid. Dahalokely is the only known dinosaur from the interval during which Indo-Madagascar likely existed as a distinct landmass, but more complete material is needed to evaluate whether or not it is more closely related to later abelisauroids of Indo-Madagascar or those known elsewhere in Gondwana. PMID:23637961

Farke, Andrew A.; Sertich, Joseph J. W.

2013-01-01

362

An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures.  

PubMed

Ornithischia is one of the two major groups of dinosaurs, with heterodontosauridae as one of its major clades. Heterodontosauridae is characterized by small, gracile bodies and a problematic phylogenetic position. Recent phylogenetic work indicates that it represents the most basal group of all well-known ornithischians. Previous heterodontosaurid records are mainly from the Early Jurassic period (205-190 million years ago) of Africa. Here we report a new heterodontosaurid, Tianyulong confuciusi gen. et sp. nov., from the Early Cretaceous period (144-99 million years ago) of western Liaoning Province, China. Tianyulong extends the geographical distribution of heterodontosaurids to Asia and confirms the clade's previously questionable temporal range extension into the Early Cretaceous period. More surprisingly, Tianyulong bears long, singular and unbranched filamentous integumentary (outer skin) structures. This represents the first confirmed report, to our knowledge, of filamentous integumentary structures in an ornithischian dinosaur. PMID:19295609

Zheng, Xiao-Ting; You, Hai-Lu; Xu, Xing; Dong, Zhi-Ming

2009-03-19

363

Bone Cancer Rates in Dinosaurs Compared with Modern Vertebrates  

E-print Network

Data on the prevalence of bone cancer in dinosaurs is available from past radiological examination of preserved bones. We statistically test this data for consistency with rates extrapolated from information on bone cancer in modern vertebrates, and find that there is no evidence of a different rate. Thus, this test provides no support for a possible role of ionizing radiation in the K-T extinction event.

L. C. Natarajan; A. L. Melott; B. M. Rothschild; L. D. Martin

2007-04-15

364

No dinosaurs in microcanonical gravitation: No special "microcanonical phase transitions"  

E-print Network

It is shown that the recently introduced singularities of the microcanonical entropy like "microcanonical phase transitions", and exotic pattern of the microcanonical caloric curve T(E) like multi-valuednes or the appearance of "dinosaur's necks" are inconsistent with Boltzmann's fundamental definition of entropy S=ln[W(E)] for a system at equilibrium even for extremely large systems as astro-physical ones.

D. H. E. Gross

2003-07-22

365

Body temperatures in dinosaurs: what can growth curves tell us?  

PubMed

To estimate the body temperature (BT) of seven dinosaurs Gillooly, Alleen, and Charnov (2006) used an equation that predicts BT from the body mass and maximum growth rate (MGR) with the latter preserved in ontogenetic growth trajectories (BT-equation). The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006). I first studied whether BTs derived from the BT-equation of today's crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a larger number of dinosaurs than Gillooly, Alleen, and Charnov (2006) did. In particular, I estimated BT of Archaeopteryx (from two MGRs), ornithischians (two), theropods (three), prosauropods (three), and sauropods (nine). For extant species, the BT value estimated from the BT-equation was a poor estimate of an animal's core temperature. For birds, BT was always strongly overestimated and for crocodiles underestimated; for mammals the accuracy of BT was moderate. I argue that taxon-specific differences in the scaling of MGR (intercept and exponent of the regression line, log-log-transformed) and in the parameterization of the Arrhenius model both used in the BT-equation as well as ecological and evolutionary adaptations of species cause these inaccuracies. Irrespective of the found inaccuracy of BTs estimated from the BT-equation and contrary to the results of Gillooly, Alleen, and Charnov (2006) I found no increase in BT with increasing body mass across all dinosaurs (Sauropodomorpha, Sauropoda) studied. This observation questions that, due to overheating, the maximum size in Dinosauria was ultimately limited by BT. However, the general high inaccuracy of dinosaurian BTs derived from the BT-equation makes a reliable test of whether body size in dinosaurs was ultimately limited by overheating impossible. PMID:24204568

Griebeler, Eva Maria

2013-01-01

366

Ornithomimidae (Bird Mimics): The Ostrich-Like Dinosaurs  

NSDL National Science Digital Library

This site describes the Ornithomimids, a distinctive group of theropod dinosaurs who show a good example of convergent evolution with the ratite birds, such as ostriches. They were not as closely related to birds as the Dromaeosauridae were, but were still members of the well supported group Coelurosauria, which includes birds. The site describes their classification, morphology, locomotion, and eating habits. This site also includes active links for further study.

367

Body Temperatures in Dinosaurs: What Can Growth Curves Tell Us?  

PubMed Central

To estimate the body temperature (BT) of seven dinosaurs Gillooly, Alleen, and Charnov (2006) used an equation that predicts BT from the body mass and maximum growth rate (MGR) with the latter preserved in ontogenetic growth trajectories (BT-equation). The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006). I first studied whether BTs derived from the BT-equation of today’s crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a larger number of dinosaurs than Gillooly, Alleen, and Charnov (2006) did. In particular, I estimated BT of Archaeopteryx (from two MGRs), ornithischians (two), theropods (three), prosauropods (three), and sauropods (nine). For extant species, the BT value estimated from the BT-equation was a poor estimate of an animal’s core temperature. For birds, BT was always strongly overestimated and for crocodiles underestimated; for mammals the accuracy of BT was moderate. I argue that taxon-specific differences in the scaling of MGR (intercept and exponent of the regression line, log-log-transformed) and in the parameterization of the Arrhenius model both used in the BT-equation as well as ecological and evolutionary adaptations of species cause these inaccuracies. Irrespective of the found inaccuracy of BTs estimated from the BT-equation and contrary to the results of Gillooly, Alleen, and Charnov (2006) I found no increase in BT with increasing body mass across all dinosaurs (Sauropodomorpha, Sauropoda) studied. This observation questions that, due to overheating, the maximum size in Dinosauria was ultimately limited by BT. However, the general high inaccuracy of dinosaurian BTs derived from the BT-equation makes a reliable test of whether body size in dinosaurs was ultimately limited by overheating impossible. PMID:24204568

Griebeler, Eva Maria

2013-01-01

368

25 YEARS OF EPIDERMAL STEM CELLS  

PubMed Central

This is a chronicle of concepts in the field of epidermal stem cell biology and a historic look at their development over time. The last 25 years have seen the evolution of epidermal stem cell science, from first fundamental studies to a sophisticated science. The study of epithelial stem cell biology was aided by the ability to visualize the distribution of stem cells and their progeny through lineage analysis studies. The excellent progress we have made in understanding epidermal stem cell biology is discussed in this article. The challenges we still face in understanding epidermal stem cell include defining molecular markers for stem and progenitor subpopulations, determining the locations and contributions of the different stem cell niches, and mapping regulatory pathways of epidermal stem cell proliferation and differentiation. However, our rapidly evolving understanding of epidermal stem cells has many potential uses that promise to translate into improved patient therapy. PMID:22205306

Ghadially, Ruby

2012-01-01

369

Dental stem cells--characteristics and potential.  

PubMed

Soft dental tissues have been identified as easily accessible sources of multipotent postnatal stem cells. Dental stem cells are mesenchymal stem cells (MSC) capable of differentiating into at least three distinct cell lineages: osteo/odontogenic, adipogenic and neurogenic. They express various markers including those specific for MSC, embryonic stem cells and neural cells. Five different types of dental stem cells have been isolated from mature and immature teeth: dental pulp stem cells, stem cells from exfoliated deciduous teeth, periodontal ligament stem cells, stem cells from apical papilla and dental follicle progenitor cells. Dental stem cells may be used in dental tissue engineering including dental, enamel and periodontal tissue regeneration. They could also be used as a promising tool in potential treatment of neurodegenerative, ischemic and immune diseases. PMID:24446280

Bojic, Sanja; Volarevic, Vladislav; Ljujic, Biljana; Stojkovic, Miodrag

2014-06-01

370

Brain cancer stem cells  

Microsoft Academic Search

Cancers comprise heterogeneous cells, ranging from highly proliferative immature precursors to more differentiated cell lineages.\\u000a In the last decade, several groups have demonstrated the existence of cancer stem cells in both nonsolid solid tumors, including\\u000a some of the brain: glioblastoma multiforme (GBM), medulloblastoma, and ependymoma. These cells, like their normal counterpart\\u000a in homologous tissues, are multipotent, undifferentiated, self-sustaining, yet transformed

Sara G. M. Piccirillo; Elena Binda; Roberta Fiocco; Angelo L. Vescovi; Khalid Shah

2009-01-01

371

Philippe Matheron et Paul Gervais : deux pionniers de la découverte et de l'étude des os et des œufs de dinosaures de Provence (France)  

Microsoft Academic Search

Philippe Matheron and Paul Gervais: two pioneers of the discovery and study of dinosaur bones and eggs from Provence (France). Philippe Matheron was the first to describe dinosaur bones from Provence, and the first to discover in the history of paleontology dinosaur eggs. Paul Gervais used the shell fragments discovered by Matheron to take thin sections of dinosaur eggs for

Philippe TAQUET

372

Cell Stem Cell Induction of Multipotential Hematopoietic  

E-print Network

patients with hematologic diseases, including Fanconi anemia (Mu¨ ller et al., 2012), sickle cell anemiaCell Stem Cell Article Induction of Multipotential Hematopoietic Progenitors from Human Pluripotent Stem Cells via Respecification of Lineage-Restricted Precursors Sergei Doulatov,1,2 Linda T. Vo,1

Collins, James J.

373

A ceratopsian dinosaur from China and the early evolution of Ceratopsia  

Microsoft Academic Search

Ceratopsians (horned dinosaurs) represent one of the last and the most diverse radiations of non-avian dinosaurs. Although recent systematic work unanimously supports a basal division of Ceratopsia into parrot-like psittacosaurids and frilled neoceratopsians, the early evolution of the group remains poorly understood, mainly owing to its incomplete early fossil record. Here we describe a primitive ceratopsian from China. Cladistic analysis

Xing Xu; Peter J. Makovicky; Xiao-lin Wang; Mark A. Norell; Hai-lu You

2002-01-01

374

The Dinosaurs Were Not Alone (title provided or enhanced by cataloger)  

NSDL National Science Digital Library

This information about other types of living things that coexisted with the dinosaurs describes the major types of plants and animals that lived during the Mesozoic Era, what they did and how they interacted. It points out that the diet of dinosaurs and other animals is known through the existence of coprolites. There is also a section that describes the insects of that time.

375

A reinterpretation of dinosaur footprints with internal ridges from the Upper Cretaceous Uhangri Formation, Korea  

Microsoft Academic Search

Very unusual dinosaur footprints with radial internal ridges from the Late Cretaceous of southern Korea have been the subject of much controversy. All footprints are in black laminated mudstone\\/shale, and have gently curved cross-sections that show deformation of a flexible substrate by dinosaur footprint registration. These peculiar patterns have not been recorded at any other site in the world, although

Koo-Geun Hwang; Martin G. Lockley; Min Huh; In Sung Paik

2008-01-01

376

The socio-sexual behaviour of extant archosaurs: implications for understanding dinosaur behaviour  

Microsoft Academic Search

Dinosaur behaviour has little legacy in the fossil record and the rarity of fossil soft tissues makes it difficult to evaluate. Indirect evidence from bonebeds, trackways, nesting traces and in-group comparisons with extant Archosauria suggests that the only substantive arguments to be made for dinosaur sociality concern cranial ornamentation and herding behaviour. There is currently no reliable method to determine

Timothy E. Isles

2009-01-01

377

Possible oviraptorosaur (Theropoda, Dinosauria) specimens from the Early Cretaceous Otway Group of Dinosaur Cove, Australia  

Microsoft Academic Search

The Early Cretaceous Otway and Strzelecki Groups exposed on the southern coast of Victoria, Australia, have produced a fauna of dinosaurs that lived within the Antarctic Circle. As many as five or six species of hypsilophodontids numerically dominate the collections from there, but the rarer and more fragmentary theropod remains suggest a surprising diversity of carnivorous dinosaurs. A possible surangular

P. J. Currie; P. Vickers-Rich; T. H. Rich

1996-01-01

378

Sexual maturity in growing dinosaurs does not fit reptilian growth models  

PubMed Central

Recent histological studies suggest relatively rapid growth in dinosaurs. However, the timing of reproductive maturity (RM) in dinosaurs is poorly known because unambiguous indicators of RM are rare. One exception is medullary bone (MB), which is an ephemeral bony tissue that forms before ovulation in the marrow cavities of birds as a calcium source for eggshelling. Recently, MB also was described in a single specimen of the saurischian dinosaur Tyrannosaurus rex. Here, we report two other occurrences of MB: in another saurischian dinosaur, Allosaurus, and in the ornithischian dinosaur Tenontosaurus. We show by counting lines of arrested growth and performing growth curve reconstructions that Tenontosaurus, Allosaurus, and Tyrannosaurus were reproductively mature by 8, 10, and 18 years, respectively. RM in these dinosaurs coincided with a transition from growth acceleration to deceleration. It also far precedes predictions based on the growth rates of living reptiles scaled to similar size. Despite relatively rapid growth, dinosaurs were similar to reptiles in that RM developed before reaching asymptotic size. However, this reproductive strategy also occurs in medium- to large-sized mammals and correlates with a strategy of prolonged multiyear growth. RM in actively growing individuals suggests that these dinosaurs were born relatively precocial and experienced high adult mortality. The origin of the modern avian reproductive strategy in ornithuran birds likely coincided with their extreme elevations in growth rate and truncations to growth duration. PMID:18195356

Lee, Andrew H.; Werning, Sarah

2008-01-01

379

The first Lower Jurassic dinosaur from Scotland: limb bone of a ceratosaur theropod from Skye  

E-print Network

The first Lower Jurassic dinosaur from Scotland: limb bone of a ceratosaur theropod from Skye M. J right tibia of a carnivorous dinosaur is reported from the Lower Jurassic Broadford Beds Formation widespread during the Early Jurassic. This tibia, and a partial sauropod tibia from the Middle Jurassic

Benton, Michael

380

Occurrence of sauropod dinosaur tracks in the Upper Jurassic of Chile (redescription of Iguanodonichnus frenki)  

E-print Network

Occurrence of sauropod dinosaur tracks in the Upper Jurassic of Chile (redescription studied Upper Jurassic dinosaur unit in South America, the Ban~os del Flaco Formation, Chile characteristics might give clues about the pes morphology of the South American Jurassic sauropods, whose foot

Benton, Michael

381

NEW INFORMATION ON SEGISAURUS HALLI, A SMALL THEROPOD DINOSAUR FROM THE EARLY JURASSIC OF ARIZONA  

E-print Network

NEW INFORMATION ON SEGISAURUS HALLI, A SMALL THEROPOD DINOSAUR FROM THE EARLY JURASSIC OF ARIZONA, a small Early Jurassic dinosaur and the only theropod known from the Navajo Sandstone. Our study the Lower Jurassic Navajo Sandstone of Arizona (UCMP locality V3308). In his original description, Camp

Hutchinson, John

382

Stem Cells  

MedlinePLUS

Stem cells are cells with the potential to develop into many different types of cells in the body. They serve as a repair ... body. There are two main types of stem cells: embryonic stem cells and adult stem cells. Stem ...

383

Existence of Reserve Quiescent Stem Cells in Adults, From Amphibians to Humans  

Microsoft Academic Search

\\u000a Several theories have been proposed to explain the phenomenon of tissue restoration in amphibians and higher order animals.\\u000a These theories include dedifferentiation of damaged tissues, transdifferentiation of lineage-committed stem cells, and activation\\u000a of quiescent stem cells. Young and colleagues demonstrated that connective tissues throughout the body contain multiple populations\\u000a of quiescent lineagecommitted progenitor stem cells and lineage-uncommitted pluripotent stem cells.

H. E. Young

384

Geometric cues for directing the differentiation of mesenchymal stem cells  

E-print Network

Geometric cues for directing the differentiation of mesenchymal stem cells Kristopher A. Kiliana that influence the lineage commitment of stem cells. This paper demonstrates that cell shape, independent of soluble factors, has a strong influence on the differentiation of human mesenchymal stem cells (MSCs) from

Mrksich, Milan

385

Biomimetic interfacial interpenetrating polymer networks control neural stem cell behavior  

Microsoft Academic Search

Highly-regulated signals surrounding stem cells, such as growth factors at specific concentrations and matrix mechanical stiffness, have been implicated in modulating stem cell proliferation and maturation. However, tight con- trol of proliferation and lineage commitment signals is rarely achieved during growth outside the body, since the spectrum of biochemical and mechanical signals that govern stem cell renewal and maturation are

Krishanu Saha; Elizabeth F. Irwin; Julia Kozhukh; David V. Schaffer; Kevin E. Healy

2007-01-01

386

Adipose-Derived Stem Cells for Regenerative Medicine  

Microsoft Academic Search

Abstract—The emerging field of regenerative medicine will require a reliable source of stem cells in addition to biomaterial scaffolds and cytokine growth factors. Adipose tissue represents an abundant and accessible source of adult stem cells with the ability to differentiate along multiple lineage pathways. The isolation, characterization, and preclinical and clinical application of adipose-derived stem cells (ASCs) are reviewed in

Gary Lopaschuk; Jeffrey M. Gimble; Adam J. Katz; Bruce A. Bunnell

2010-01-01

387

Cell Stem Cell Limited Acquisition of Chromosomal Aberrations  

E-print Network

Cell Stem Cell Letters Limited Acquisition of Chromosomal Aberrations in Human Adult Mesenchymal 4Emory University Winship Cancer Institute, Atlanta, GA 30322, USA 5Section of Hematology, Stem Cell Acquisition of Lineage- Specific Chromosomal Aberrations in Human Adult Stem Cells,'' Ben-David and colleagues

Paris-Sud XI, Université de

388

Generation of oligodendroglial cells by direct lineage conversion  

PubMed Central

Transplantation of oligodendrocyte precursor cells (OPCs) is a promising potential therapeutic strategy for diseases affecting myelin. However, the derivation of engraftable OPCs from human pluripotent stem cells has proven difficult and primary OPCs are not readily available. Here we report the generation of induced OPCs (iOPCs) by direct lineage conversion. Forced expression of the three transcription factors Sox10, Olig2 and Zfp536 was sufficient to reprogram mouse and rat fibroblasts into iOPCs with morphologies and gene expression signatures resembling primary OPCs. More importantly, iOPCs gave rise to mature oligodendrocytes that could ensheath multiple host axons when co-cultured with primary dorsal root ganglion cells and formed myelin after transplantion into shiverer mice. We propose direct lineage reprogramming as a viable alternative approach for the generation of OPCs for use in disease modeling and regenerative medicine. PMID:23584610

Yang, Nan; Zuchero, J. Bradley; Ahlenius, Henrik; Marro, Samuele; Ng, Yi Han; Vierbuchen, Thomas; Hawkins, John S.; Geissler, Richard; Barres, Ben A.; Wernig, Marius

2013-01-01

389

Transdifferentiation of Stem Cells: A Critical View  

Microsoft Academic Search

\\u000a Recently a large amount of new data on the plasticity of stem cells of various lineages have emerged, providing new perspectives\\u000a especially for the therapeutic application of adult stem cells. Previously unknown possibilities of cell differentiation beyond\\u000a the known commitment of a given stem cell have been described using keywords such as “blood to liver,” or “bone to brain.”\\u000a Controversies

Ina Gruh; Ulrich Martin

2009-01-01

390

Matrix elasticity directs stem cell differentiation in 3D too  

NASA Astrophysics Data System (ADS)

Microenvironments appear important in stem cell lineage specification but can be difficult to adequately characterize or control with soft tissues. Naive mesenchymal stem cells (MSCs) are shown here to specify lineage andcommit to phenotypes with extreme sensitivity to tissue level elasticity. Soft matrices that mimic brain are neurogenic, stiffer matrices that mimic muscle are myogenic, and comparatively rigid matrices that mimic collagenous bone prove osteogenic. During the initial week in culture, reprogramming of these lineages is possible with addition of soluble induction factors, but after several weeks in culture, the cells commit to the lineage specified by matrix elasticity, consistent with the elasticity-insensitive commitment of differentiated cell types. Inhibition of nonmuscle myosin II blocks all elasticitydirected lineage specification--without strongly perturbing many other aspects of cell function and shape. The results have significant implications for understanding physical effects of the in vivo microenvironment and also for therapeutic uses of stem cells.

Zajac, Allison; Rehfeldt, Florian; Discher, Dennis

2009-03-01

391

Use of ground penetrating radar in detecting fossilized dinosaur bones  

NASA Astrophysics Data System (ADS)

Ground penetrating radar (GPR) has been used successfully to help archaeologists locate building foundations and other artifacts of past civilizations. Yet, little has been done to help paleontologists in their search for fossilized remains. Fossilized and partially fossilized dinosaur bones are located in a sandstone outcrop at the Dinosaur Ridge Natural Landmark outside Morrison, Colorado. The bones are located within a cliff face and in two large boulders located along the road. Little work has been done to characterize the size of these bones and to study the possibility of bones located deeper within the sandstone cliff face. Mineralogical studies have shown that these bones contain approximately 15% iron oxides (Fe2O3) along with smaller percentages of MgO and Al2O3. Due to the presence of Fe2O3, as strong reflection is expected on the GPR record. Data have been collected along the cliff face using a Sensors and Software pulseEKKO 1000 900 MHz antenna. The area of interest measures approximately 1 meter high and 3.5 meters long. Several strong hyperbolas stand out in the raw and processed data. Velocity estimations show the depth of investigation to be greater than 1.1 meters. Data have been collected along crosslines in order to judge size and orientation of any anomalies discovered. Full waveform modeling was performed on traces showing anomalies to better characterize the dielectric permittivity and magnetic permeability. These results will be analyzed to determine what anomalies have the possibility of being dinosaur bones.

Meglich, Todd M.

2000-04-01

392

Characterization of human mesenchymal stem cell secretome at early steps of adipocyte and osteoblast differentiation  

Microsoft Academic Search

BACKGROUND: It is well established that adipose tissue plays a key role in energy storage and release but is also a secretory organ and a source of stem cells. Among different lineages, stem cells are able to differentiate into adipocytes and osteoblasts. As secreted proteins could regulate the balance between both lineages, we aimed at characterizing the secretome of human

Chiara Chiellini; Olivia Cochet; Luc Negroni; Michel Samson; Marjorie Poggi; Gérard Ailhaud; Marie-Christine Alessi; Christian Dani; Ez-Zoubir Amri

2008-01-01

393

Localization of Putative Stem Cells in Dental Epithelium and Their Association with Notch and FGF Signaling  

Microsoft Academic Search

The continuously growing mouse incisor is an excellent model to analyze the mechanisms for stem cell lineage. We designed an organ culture method for the apical end of the incisor and analyzed the epithelial cell lineage by 5-bromo-2 9 -deoxyuridine and DiI label- ing. Our results indicate that stem cells reside in the cervical loop epithelium consisting of a central

Hidemitsu Harada; Päivi Kettunen; Han-Sung Jung; Tuija Mustonen; Y. Alan Wang; Irma Thesleff

1999-01-01

394

CELL LINEAGE PROJECTIONS IN LOW DIMENSIONAL SPACES Sabina Pfister*, Colette Dehay**, Henry Kennedy**, Rodney Douglas*  

E-print Network

CELL LINEAGE PROJECTIONS IN LOW DIMENSIONAL SPACES Sabina Pfister*, Colette Dehay**, Henry Kennedy**, Rodney Douglas* *Institute of Neuroinformatics, UNI/ETH, Zürich, Switzerland **Stem-cell and Brain@ini.phys.ethz.ch ABSTRACT Cortical neurogenesis is a complex process during which dividing cells have the ability to acquire

Paris-Sud XI, Université de

395

Distinct populations of adipogenic and myogenic Myf5-lineage progenitors in white adipose tissues[S  

PubMed Central

Brown adipose tissues (BAT) are derived from a myogenic factor 5 (Myf5)-expressing cell lineage and white adipose tissues (WAT) predominantly arise from non-Myf5 lineages, although a subpopulation of adipocytes in some WAT depots can be derived from the Myf5 lineage. However, the functional implication of the Myf5- and non-Myf5-lineage cells in WAT is unclear. We found that the Myf5-lineage constitution in subcutaneous WAT depots is negatively correlated to the expression of classical BAT and newly defined beige/brite adipocyte-specific genes. Consistently, fluorescent-activated cell sorting (FACS)-purified Myf5-lineage adipo-progenitors give rise to adipocytes expressing lower levels of BAT-specific Ucp1, Prdm16, Cidea, and Ppargc1a genes and beige adipocyte-specific CD137, Tmem26, and Tbx1 genes compared with the non-Myf5-lineage adipocytes from the same depots. Ablation of the Myf5-lineage progenitors in WAT stromal vascular cell (SVC) cultures leads to increased expression of BAT and beige cell signature genes. Strikingly, the Myf5-lineage cells in WAT are heterogeneous and contain distinct adipogenic [stem cell antigen 1(Sca1)-positive] and myogenic (Sca1-negative) progenitors. The latter differentiate robustly into myofibers in vitro and in vivo, and they restore dystrophin expression after transplantation into mdx mouse, a model for Duchenne muscular dystrophy. These results demonstrate the heterogeneity and functional differences of the Myf5- and non-Myf5-lineage cells in the white adipose tissue. PMID:23740968

Shan, Tizhong; Liang, Xinrong; Bi, Pengpeng; Zhang, Pengpeng; Liu, Weiyi; Kuang, Shihuan

2013-01-01

396

Turanoceratops tardabilis—the first ceratopsid dinosaur from Asia  

NASA Astrophysics Data System (ADS)

Turanoceratops tardabilis from the Upper Cretaceous (Turonian) Bissekty Formation of Dzharakuduk, Uzbekistan, represents the first definite ceratopsid dinosaur recorded from Asia. Reexamination of the original and study of newly collected material indicate that Turanoceratops has well-developed supraorbital horns and apparently lacks a nasal horn. Turanoceratops is more derived than the more or less coeval Zuniceratops from the Moreno Hill Formation of New Mexico in the presence of double-rooted teeth and of two or three teeth in each vertical dental file.

Sues, Hans-Dieter; Averianov, Alexander

2009-05-01

397

Reworking of Cretaceous dinosaurs into Paleocene channel deposits, upper Hell Creek Formation, Montana  

SciTech Connect

Dinosaur teeth from Paleocene channel fills have been interpreted as indicating dinosaur survival into the Paleocene. However, enormous potential for reworking exists because these records are restricted to large channel fills that are deeply incised into Cretaceous strata. Identification of reworked fossils is usually equivocal. This problem is illustrated by the Black Spring Coulee channel fill, a dinosaur-bearing Paleocene deposit in the upper Hell Creek Formation of eastern Montana. In this example, the reworked nature of well-preserved dinosaur bones is apparent only after detailed sedimentological and palynological analysis. Because of the potential for reworking, dinosaur remains derived from Paleocene fluvial deposits should not be assigned a Paleocene age unless the (1) are found in floodplain deposits, (2) are articulated, (3) are in channels that do not incise Cretaceous strata, or (4) are demonstrably reworked from Paleocene deposits. To date, reports of Paleocene dinosaurs do not fulfill any of these criteria. Thus, the proposal that dinosaurs persisted into the Paleocene remains unsubstantiated.

Lofgren, D.L. (Univ. of California, Berkeley (USA)); Hotton, C.L. (State Univ. of New York, Binghamton (USA)); Runkel, A.C. (Univ. of Texas, Austin (USA))

1990-09-01

398

Dinosaur eggshell geochemistry as an indicator of Central Asian Cretaceous paleoenvironments  

NASA Astrophysics Data System (ADS)

The Late Cretaceous fossiliferous beds of Mongolia's Gobi Desert have yielded spectacular articulated remains of an extraordinary diversity of fossil mammals, reptiles, birds, and dinosaurs. Paleoenvironmental interpretations of the deposits at these localities have ranged from arid wind-blown dune fields to more mesic, moist environments. Among the diversity of fossils, dinosaur eggshells are commonly found at these localities and dinosaur embryos, although rare, are also encountered. Dinosaur (including modern bird) eggs are constructed of calcite (CaCO3) allowing carbon and oxygen stable isotopes to be quantified to provide information about the environment the egg-laying animals were living in. Here we show that dinosaur eggshell from the Djadokhta Formation at one locality has not been significantly altered and reflects an environment that of dry-climate adapted C3 plants and isolated, ephemeral water sources during the egg-laying season. Carbonate nodules from the same eggshell-bearing layers also independently reflects a similar environmental signal. This study represents the first geochemical analysis of dinosaur remains from the Cretaceous of Mongolia and illustrates the potential of utilizing dinosaur eggshell geochemistry to reconstruct Mesozoic environments.
Mean, n, standard deviation, and range for both carbon and oxygen isotope values for all materials sampled

Montanari, S.; Higgins, P.; Norell, M.

2011-12-01

399

Out of the Box Thinking: Kinematics from a 163 Million-Year-Old Dinosaur Trackway  

NASA Astrophysics Data System (ADS)

Dinosaurs always grab the interest of students. Information about dinosaur locomotion is accessible from the trackways they left. In a unique connection to kinematics, evidence of the acceleration of a meat-eating dinosaur (theropod) is evident in Trackway 13 in Ardley Quarry in Oxfordshire, UK. This particular trackway is described by J.J. Day, D.B. Norman, P. Upchuch and H.P. Powell in Vol. 415 of Nature on pages 494 and 495, published in 2002. This particular theropod underwent an acceleration of about g/3. This example provides a fun and engaging exercise for students studying kinematics.

Lee, Scott

2012-02-01

400

Phylogenetic lineages in the Botryosphaeriaceae  

PubMed Central

Botryosphaeria is a species-rich genus with a cosmopolitan distribution, commonly associated with dieback and cankers of woody plants. As many as 18 anamorph genera have been associated with Botryosphaeria, most of which have been reduced to synonymy under Diplodia (conidia mostly ovoid, pigmented, thick-walled), or Fusicoccum (conidia mostly fusoid, hyaline, thin-walled). However, there are numerous conidial anamorphs having morphological characteristics intermediate between Diplodia and Fusicoccum, and there are several records of species outside the Botryosphaeriaceae that have anamorphs apparently typical of Botryosphaeria s.str. Recent studies have also linked Botryosphaeria to species with pigmented, septate ascospores, and Dothiorella anamorphs, or Fusicoccum anamorphs with Dichomera synanamorphs. The aim of this study was to employ DNA sequence data of the 28S rDNA to resolve apparent lineages within the Botryosphaeriaceae. From these data, 12 clades are recognised. Two of these lineages clustered outside the Botryosphaeriaceae, namely Diplodia-like anamorphs occurring on maize, which are best accommodated in Stenocarpella (Diaporthales), as well as an unresolved clade including species of Camarosporium/Microdiplodia. We recognise 10 lineages within the Botryosphaeriaceae, including an unresolved clade (Diplodia/Lasiodiplodia/Tiarosporella), Botryosphaeria s.str. (Fusicoccum anamorphs), Macrophomina, Neoscytalidium gen. nov., Dothidotthia (Dothiorella anamorphs), Neofusicoccum gen. nov. (Botryosphaeria-like teleomorphs, Dichomera-like synanamorphs), Pseudofusicoccum gen. nov., Saccharata (Fusicoccum- and Diplodia-like synanamorphs), “Botryosphaeria” quercuum (Diplodia-like anamorph), and Guignardia (Phyllosticta anamorphs). Separate teleomorph and anamorph names are not provided for newly introduced genera, even where both morphs are known. The taxonomy of some clades and isolates (e.g. B. mamane) remains unresolved due to the absence of ex-type cultures. PMID:18490983

Crous, Pedro W.; Slippers, Bernard; Wingfield, Michael J.; Rheeder, John; Marasas, Walter F.O.; Philips, Alan J.L.; Alves, Artur; Burgess, Treena; Barber, Paul; Groenewald, Johannes Z.

2006-01-01

401

Secondary Cartilage Revealed in a Non-Avian Dinosaur Embryo  

PubMed Central

The skull and jaws of extant birds possess secondary cartilage, a tissue that arises after bone formation during embryonic development at articulations, ligamentous and muscular insertions. Using histological analysis, we discovered secondary cartilage in a non-avian dinosaur embryo, Hypacrosaurus stebingeri (Ornithischia, Lambeosaurinae). This finding extends our previous report of secondary cartilage in post-hatching specimens of the same dinosaur species. It provides the first information on the ontogeny of avian and dinosaurian secondary cartilages, and further stresses their developmental similarities. Secondary cartilage was found in an embryonic dentary within a tooth socket where it is hypothesized to have arisen due to mechanical stresses generated during tooth formation. Two patterns were discerned: secondary cartilage is more restricted in location in this Hypacrosaurus embryo, than it is in Hypacrosaurus post-hatchlings; secondary cartilage occurs at far more sites in bird embryos and nestlings than in Hypacrosaurus. This suggests an increase in the number of sites of secondary cartilage during the evolution of birds. We hypothesize that secondary cartilage provided advantages in the fine manipulation of food and was selected over other types of tissues/articulations during the evolution of the highly specialized avian beak from the jaws of their dinosaurian ancestors. PMID:23418610

Bailleul, Alida M.; Hall, Brian K.; Horner, John R.

2013-01-01

402

Bioprinting for stem cell research  

PubMed Central

Recently, there has been a growing interest to apply bioprinting techniques to stem cell research. Several bioprinting methods have been developed utilizing acoustics, piezoelectricity, and lasers to deposit living cells onto receiving substrates. Using these technologies, spatially defined gradients of immobilized proteins can be engineered to direct stem cell differentiation into multiple subpopulations of different lineages. Stem cells can also be patterned in a high-throughput manner onto flexible implementation patches for tissue regeneration or onto substrates with the goal of accessing encapsulated stem cell of interest for genomic analysis. Here, we review recent achievements with bioprinting technologies in stem cell research, and identify future challenges and potential applications including tissue engineering and regenerative medicine, wound healing, and genomics. PMID:23260439

Tasoglu, Savas; Demirci, Utkan

2012-01-01

403

Author's personal copy Rolling bones Taphonomy of Jurassic dinosaur bones inferred from diagenetic  

E-print Network

, the altered chemical composition of fossil bones, especially rare earth elements (REE) (e.g. Trueman and Bento their fossilization. Characteristic desiccation cracks in the dinosaur bones indicate deposition on the soil surface

Schöne, Bernd R.

404

Evidence of the growth plate and the growth of long bones in juvenile dinosaurs.  

PubMed

Histological and ultrastructural evaluation of the ends of long bones of juvenile dinosaurs from the Upper Cretaceous Two Medicine Formation of Montana revealed the preservation of growth plates. Growth plates are discs of cartilage present near the ends of growing long bones that generate bone elongation. Comparison of the fossils with modern taxa demonstrated homology of the growth plate in birds and dinosaurs. The presence of an avian-type growth plate in dinosaurs adds a shared derived anatomical character corroborating inclusion of birds within the Dinosauria. Additionally, possession of a growth plate, which in birds is capable of producing rapid determinate long bone growth, implies that an avian developmental pattern may have been present in these dinosaurs. PMID:17794968

Barreto, C; Albrecht, R M; Bjorling, D E; Horner, J R; Wilsman, N J

1993-12-24

405

Study Documents Bird-like Breathing Systems in Long-extinct Dinosaurs  

NSF Publications Database

... to living reptiles, like crocodiles. The avian pulmonary system uses "flow-through ventilation ... to have been present in dinosaurs, so, many avian features may really be dinosaurian," said O'Connor ...

406

Divergent functions of hematopoietic transcription factors in lineage priming and differentiation during erythro-megakaryopoiesis  

PubMed Central

Combinatorial actions of relatively few transcription factors control hematopoietic differentiation. To investigate this process in erythro-megakaryopoiesis, we correlated the genome-wide chromatin occupancy signatures of four master hematopoietic transcription factors (GATA1, GATA2, TAL1, and FLI1) and three diagnostic histone modification marks with the gene expression changes that occur during development of primary cultured megakaryocytes (MEG) and primary erythroblasts (ERY) from murine fetal liver hematopoietic stem/progenitor cells. We identified a robust, genome-wide mechanism of MEG-specific lineage priming by a previously described stem/progenitor cell-expressed transcription factor heptad (GATA2, LYL1, TAL1, FLI1, ERG, RUNX1, LMO2) binding to MEG-associated cis-regulatory modules (CRMs) in multipotential progenitors. This is followed by genome-wide GATA factor switching that mediates further induction of MEG-specific genes following lineage commitment. Interaction between GATA and ETS factors appears to be a key determinant of these processes. In contrast, ERY-specific lineage priming is biased toward GATA2-independent mechanisms. In addition to its role in MEG lineage priming, GATA2 plays an extensive role in late megakaryopoiesis as a transcriptional repressor at loci defined by a specific DNA signature. Our findings reveal important new insights into how ERY and MEG lineages arise from a common bipotential progenitor via overlapping and divergent functions of shared hematopoietic transcription factors. PMID:25319996

Pimkin, Maxim; Kossenkov, Andrew V.; Mishra, Tejaswini; Morrissey, Christapher S.; Wu, Weisheng; Keller, Cheryl A.; Blobel, Gerd A.; Lee, Dongwon; Beer, Michael A.; Hardison, Ross C.

2014-01-01

407

Implications of ecological energetics and biophysical and developmental constraints for life history variation in dinosaurs  

SciTech Connect

There has been much recent speculation concerning the nature of life history variation in dinosaurs (Case, 1978; Bakker, 1986; Horner, 1982, 1984a). The purpose of this paper is to review the data on dinosaur life histories and to examine the nature and magnitude of the demographic and physiological factors that must have constrained life history variation in this group. 145 refs., 8 figs., 3 tabs.

Dunham, A.E.; Overall, K.L.; Forster, C.A.; Porter, W.P.

1988-01-01

408

Non-avian theropod dinosaurs from the early Late Cretaceous of central Europe  

Microsoft Academic Search

Quantitative and qualitative analyses of isolated teeth and postcranial elements of non-avian theropod dinosaurs from the Upper Cretaceous (Santonian) Csehbánya Formation, Iharkút (western Hungary) indicate that these remains represent multiple dinosaur groups. Based on comparative and statistical analyses, 58 teeth and tooth fragments are identified as belonging to medium-sized basal tetanuran theropods that may have represented the top-predator of the

Attila ?si; Sebastián Apesteguía; Micha? Kowalewski

2010-01-01

409

Boom and bust: ancient and recent diversification in bichirs (Polypteridae: Actinopterygii), a relictual lineage of ray-finned fishes.  

PubMed

Understanding the history that underlies patterns of species richness across the Tree of Life requires an investigation of the mechanisms that not only generate young species-rich clades, but also those that maintain species-poor lineages over long stretches of evolutionary time. However, diversification dynamics that underlie ancient species-poor lineages are often hidden due to a lack of fossil evidence. Using information from the fossil record and time calibrated molecular phylogenies, we investigate the history of lineage diversification in Polypteridae, which is the sister lineage of all other ray-finned fishes (Actinopterygii). Despite originating at least 390 million years (Myr) ago, molecular timetrees support a Neogene origin for the living polypterid species. Our analyses demonstrate polypterids are exceptionally species depauperate with a stem lineage duration that exceeds 380 million years (Ma) and is significantly longer than the stem lineage durations observed in other ray-finned fish lineages. Analyses of the fossil record show an early Late Cretaceous (100.5-83.6 Ma) peak in polypterid genus richness, followed by 60 Ma of low richness. The Neogene species radiation and evidence for high-diversity intervals in the geological past suggest a "boom and bust" pattern of diversification that contrasts with common perceptions of relative evolutionary stasis in so-called "living fossils." PMID:24274466

Near, Thomas J; Dornburg, Alex; Tokita, Masayoshi; Suzuki, Dai; Brandley, Matthew C; Friedman, Matt

2014-04-01

410

First trace and body fossil evidence of a burrowing, denning dinosaur  

PubMed Central

A fossil discovery in the mid-Cretaceous Blackleaf Formation of southwest Montana, USA, has yielded the first trace and body fossil evidence of burrowing behaviour in a dinosaur. Skeletal remains of an adult and two juveniles of Oryctodromeus cubicularis gen. et sp. nov., a new species of hypsilophodont-grade dinosaur, were found in the expanded distal chamber of a sediment-filled burrow. Correspondence between burrow and adult dimensions supports Oryctodromeus as the burrow maker. Additionally, Oryctodromeus exhibits features of the snout, shoulder girdle and pelvis consistent with digging habits while retaining cursorial hindlimb proportions. Association of adult and young within a terminal chamber provides definitive evidence of extensive parental care in the Dinosauria. As with modern vertebrate cursors that dig, burrowing in Oryctodromeus may have been an important adaptation for the rearing of young. Burrowing also represents a mechanism by which small dinosaurs may have exploited the extreme environments of polar latitudes, deserts and high mountain areas. The ability among dinosaurs to find or make shelter may contradict some scenarios of the Cretaceous–Paleogene impact event. Burrowing habits expand the known range of nonavian dinosaur behaviours and suggest that the cursorial ancestry of dinosaurs did not fully preclude the evolution of different functional regimes, such as fossoriality. PMID:17374596

Varricchio, David J; Martin, Anthony J; Katsura, Yoshihiro

2007-01-01

411

Oxygen isotopes from biogenic apatites suggest widespread endothermy in Cretaceous dinosaurs  

NASA Astrophysics Data System (ADS)

The much debated question of dinosaur thermophysiology has not yet been conclusively solved despite numerous attempts. We used the temperature-dependent oxygen isotope fractionation between vertebrate body water (? 18O body water) and phosphatic tissues (? 18O p) to compare the thermophysiology of dinosaurs with that of non-dinosaurian ectothermic reptiles. Present-day ? 18O p values of vertebrate apatites show that ectotherms have higher ? 18O p values than endotherms at high latitudes due to their lower body temperature, and conversely lower ? 18O p values than endotherms at low latitudes. Using a data set of 80 new and 49 published ? 18O p values, we observed similar and systematic differences in ? 18O p values (? 18O) between four groups of Cretaceous dinosaurs (theropods, sauropods, ornithopods and ceratopsians) and associated fresh water crocodiles and turtles. Expressed in terms of body temperatures ( Tb), these ? 18O values indicate that dinosaurs maintained rather constant Tb in the range of endotherms whatever ambient temperatures were. This implies that high metabolic rates were widespread among Cretaceous dinosaurs belonging to widely different taxonomic groups and suggest that endothermy may be a synapomorphy of dinosaurs, or may have been acquired convergently in the studied taxa.

Amiot, Romain; Lécuyer, Christophe; Buffetaut, Eric; Escarguel, Gilles; Fluteau, Frédéric; Martineau, François

2006-06-01

412

First trace and body fossil evidence of a burrowing, denning dinosaur.  

PubMed

A fossil discovery in the mid-Cretaceous Blackleaf Formation of southwest Montana, USA, has yielded the first trace and body fossil evidence of burrowing behaviour in a dinosaur. Skeletal remains of an adult and two juveniles of Oryctodromeus cubicularis gen. et sp. nov. a new species of hypsilophodont-grade dinosaur, were found in the expanded distal chamber of a sediment-filled burrow. Correspondence between burrow and adult dimensions supports Oryctodromeus as the burrow maker. Additionally, Oryctodromeus exhibits features of the snout, shoulder girdle and pelvis consistent with digging habits while retaining cursorial hindlimb proportions. Association of adult and young within a terminal chamber provides definitive evidence of extensive parental care in the Dinosauria. As with modern vertebrate cursors that dig, burrowing in Oryctodromeus may have been an important adaptation for the rearing of young. Burrowing also represents a mechanism by which small dinosaurs may have exploited the extreme environments of polar latitudes, deserts and high mountain areas. The ability among dinosaurs to find or make shelter may contradict some scenarios of the Cretaceous-Paleogene impact event. Burrowing habits expand the known range of nonavian dinosaur behaviours and suggest that the cursorial ancestry of dinosaurs did not fully preclude the evolution of different functional regimes, such as fossoriality. PMID:17374596

Varricchio, David J; Martin, Anthony J; Katsura, Yoshihiro

2007-06-01

413

Generalized Potential of Adult Neural Stem Cells  

NASA Astrophysics Data System (ADS)

The differentiation potential of stem cells in tissues of the adult has been thought to be limited to cell lineages present in the organ from which they were derived, but there is evidence that some stem cells may have a broader differentiation repertoire. We show here that neural stem cells from the adult mouse brain can contribute to the formation of chimeric chick and mouse embryos and give rise to cells of all germ layers. This demonstrates that an adult neural stem cell has a very broad developmental capacity and may potentially be used to generate a variety of cell types for transplantation in different diseases.

Clarke, Diana L.; Johansson, Clas B.; Wilbertz, Johannes; Veress, Biborka; Nilsson, Erik; Karlström, Helena; Lendahl, Urban; Frisén, Jonas

2000-06-01

414

CD117+ amniotic fluid stem cells  

PubMed Central

Broadly multipotent stem cells can be isolated from amniotic fluid by selection for the expression of the membrane stem cell factor receptor c-Kit, a common marker for multipotential stem cells. They have clonogenic capability and can be directed into a wide range of cell types representing the three primary embryonic lineages. Amniotic fluid stem cells maintained for over 250 population doublings retained long telomeres and a normal karyotype. Clonal human lines verified by retroviral marking were induced to differentiate into cell types representing each embryonic germ layer, including cells of adipogenic, osteogenic, myogenic, endothelial, neuronal and hepatic lineages. AFS cells could be differentiate toward cardiomyogenic lineages, when co-cultured with neonatal cardiomyocytes, and have the potential to generate myogenic and hematopoietic lineages both in vitro and in vivo. Very recently first trimester AFS cells could be reprogrammed without any genetic manipulation opening new possibilities in the field of fetal/neonatal therapy and disease modeling. In this review we are aiming to summarize the knowledge on amniotic fluid stem cells and highlight the most promising results. PMID:23037870

Cananzi, Mara; De Coppi, Paolo

2012-01-01

415

Analysis of complete neuroblast cell lineages in the Drosophila embryonic brain via DiI labeling.  

PubMed

Proper functioning of the brain relies on an enormous diversity of neural cells generated by neural stem cell-like neuroblasts (NBs). Each of the about 100 NBs in each side of brain generates a nearly invariant and unique cell lineage, consisting of specific neural cell types that develop in defined time periods. In this chapter we describe a method that labels entire NB lineages in the embryonic brain. Clonal DiI labeling allows us to follow the development of a NB lineage starting from the neuroectodermal precursor cell up to the fully developed cell clone in the first larval instar brain. We also show how to ablate individual cells within a NB clone, which reveals information about the temporal succession in which daughter cells are generated. Finally, we describe how to combine clonal DiI labeling with fluorescent antibody staining that permits relating protein expression to individual cells within a labeled NB lineage. These protocols make it feasible to uncover precise lineage relationships between a brain NB and its daughter cells, and to assign gene expression to individual clonal cells. Such lineage-based information is a critical key for understanding the cellular and molecular mechanisms that underlie specification of cell fates in spatial and temporal dimension in the embryonic brain. PMID:24048925

Kraft, Karoline F; Urbach, Rolf

2014-01-01

416

New dinosaurs link southern landmasses in the Mid-Cretaceous.  

PubMed Central

Abelisauroid predators have been recorded almost exclusively from South America, India and Madagascar, a distribution thought to document persistent land connections exclusive of Africa. Here, we report fossils from three stratigraphic levels in the Cretaceous of Niger that provide definitive evidence that abelisauroid dinosaurs and their immediate antecedents were also present on Africa. The fossils include an immediate abelisauroid antecedent of Early Cretaceous age (ca. 130-110 Myr ago), early members of the two abelisauroid subgroups (Noasauridae, Abelisauridae) of Mid-Cretaceous age (ca. 110 Myr ago) and a hornless abelisaurid skull of early Late Cretaceous age (ca. 95 Myr ago). Together, these fossils fill in the early history of the abelisauroid radiation and provide key evidence for continued faunal exchange among Gondwanan landmasses until the end of the Early Cretaceous (ca. 100 Myr ago). PMID:15306329

Sereno, Paul C.; Wilson, Jeffrey A.; Conrad, Jack L.

2004-01-01

417

Tipsy punters: sauropod dinosaur pneumaticity, buoyancy and aquatic habits.  

PubMed Central

Sauropod dinosaurs were the largest terrestrial animals to have ever existed, and are difficult to interpret as living animals owing to their lack of living descendants. With computer models that employ the basic physics of buoyancy and equilibrium, it is possible to investigate how the bodies of these animals would have reacted when immersed in water. Multi-tonne sauropods are found to be extremely buoyant and unstable in water when aspects of their probable respiratory anatomy are considered, which obviates the old problem of them being unable to breathe when fully immersed. Interpretations of 'manus-only' trackways made by floating sauropods will depend on the details of buoyancy as not all sauropods float in the same manner. PMID:15252977

Henderson, Donald M

2004-01-01

418

Evolution of High Tooth Replacement Rates in Sauropod Dinosaurs  

PubMed Central

Background Tooth replacement rate can be calculated in extinct animals by counting incremental lines of deposition in tooth dentin. Calculating this rate in several taxa allows for the study of the evolution of tooth replacement rate. Sauropod dinosaurs, the largest terrestrial animals that ever evolved, exhibited a diversity of tooth sizes and shapes, but little is known about their tooth replacement rates. Methodology/Principal Findings We present tooth replacement rate, formation time, crown volume, total dentition volume, and enamel thickness for two coexisting but distantly related and morphologically disparate sauropod dinosaurs Camarasaurus and Diplodocus. Individual tooth formation time was determined by counting daily incremental lines in dentin. Tooth replacement rate is calculated as the difference between the number of days recorded in successive replacement teeth. Each tooth family in Camarasaurus has a maximum of three replacement teeth, whereas each Diplodocus tooth family has up to five. Tooth formation times are about 1.7 times longer in Camarasaurus than in Diplodocus (315 vs. 185 days). Average tooth replacement rate in Camarasaurus is about one tooth every 62 days versus about one tooth every 35 days in Diplodocus. Despite slower tooth replacement rates in Camarasaurus, the volumetric rate of Camarasaurus tooth replacement is 10 times faster than in Diplodocus because of its substantially greater tooth volumes. A novel method to estimate replacement rate was developed and applied to several other sauropodomorphs that we were not able to thin section. Conclusions/Significance Differences in tooth replacement rate among sauropodomorphs likely reflect disparate feeding strategies and/or food choices, which would have facilitated the coexistence of these gigantic herbivores in one ecosystem. Early neosauropods are characterized by high tooth replacement rates (despite their large tooth size), and derived titanosaurs and diplodocoids independently evolved the highest known tooth replacement rates among archosaurs. PMID:23874921

Smith, Kathlyn M.; Fisher, Daniel C.; Wilson, Jeffrey A.

2013-01-01

419

Human Lineage-specific Gene Inactivation  

E-print Network

Human Lineage-specific Gene Inactivation Wendy E Grus, University of Michigan, Ann Arbor, Michigan vestiges of genes. Investigating genes that were inactivated specifically on the human lineage can reveal the genetic basis of inter- species differences between humans and chimpanzees and inter

Zhang, Jianzhi

420

Human Lineage-Specific Gene Inactivation  

E-print Network

Human Lineage-Specific Gene Inactivation Wendy E Grus, University of Michigan, Ann Arbor, Michigan vestiges of genes. Inves- tigating genes that were inactivated specifically on the human lineage or within humans can reveal the genetic basis of interspecies differences between humans and chimpanzees

Zhang, Jianzhi

421

Cretaceous Vertebrate Tracksites - Korean Cretaceous Dinosaur Coast World Heritage Nomination Site  

NASA Astrophysics Data System (ADS)

South Korea is one of the best known regions in the world for Cretaceous fossil footprints, which are also world-renowned. Korea has produced more scientifically named bird tracks (ichnotaxa) than any other region in the world. It has also produced the world's largest pterosaur tracks. Dinosaur tracksites also have the highest frequency of vertebrate track-bearing levels currently known in any stratigraphic sequence. Among the areas that have the best track records, and the greatest scientific significance with best documentation, Korea ranks very highly. Objective analysis of important individual tracksites and tracksite regions must be based on multiple criteria including: size of site, number of tracks, trackways and track bearing levels, number of valid named ichnotaxa including types, number of scientific publications, quality of preservation. The unique and distinctive dinosaur tracksites are known as one of the world's most important dinosaur track localities. In particular, the dinosaur track sites in southern coastal area of Korea are very unique. In the sites, we have excavated over 10,000 dinosaur tracks. The Hwasun sites show diverse gaits with unusual walking patterns and postures in some tracks. The pterosaur tracks are the most immense in the world. The longest pterosaur trackway yet known from any track sites suggests that pterosaurs were competent terrestrial locomotors. This ichnofauna contains the first pterosaur tracks reported from Asia. The Haenam Uhangri pterosaur assigns to a new genus Haenamichnus which accomodates the new ichnospecies, Haenamichnus uhangriensis. At least 12 track types have been reported from the Haman and Jindong Formations (probably late Lower Cretaceous). These include the types of bird tracks assigned to Koreanornis, Jindongornipes, Ignotornis and Goseongornipes. In addition the bird tracks Hwangsanipes, Uhangrichnus, the pterosaur track Haenamichnus and the dinosaur tracks, Brontopodus, Caririchnium, Minisauripus and at least three other unnamed morphotypes are known . A total of 52 clutches containing 390 dinosaur eggs occur in several stratigraphic formations including seven dinosaur egg localities. The other fossils including turtles, crocodiles, fishes, wood fossil, plants, trace fossils and microfossils have also been discovered. The occurrences of Korean dinosaurs in diverse stratigraphic formations and sedimentological setting and in diverse sizes and morphotypes provide an opportunity to study the palaeoecologic and palaeoenvironmental conditions of the sites of the Late Cretaceous dinosaurs. Korea could serve as a global vertebrate ichnological standard for Cretaceous terrestrial sequences, and allow correlation with Japanese marine sequences to the east and classic Chinese sites to the west. The region plays a pivotal role in helping us understand vertebrate evolution and paleoecology on the margins of the Asian continent during the Cretaceous.

Huh, M.; Woo, K. S.; Lim, J. D.; Paik, I. S.

2009-04-01

422

Using growth factor arrays and micropatterned co-cultures to induce hepatic differentiation of embryonic stem cells  

E-print Network

of embryonic stem cells Nazgul Tuleuova a,b , Ji Youn Lee a , Jennifer Lee a , Erlan Ramanculov b , Mark A stem cells a b s t r a c t The success in driving embryonic stem cells towards hepatic lineage has been cultivation and differentiation of mouse embryonic stem cells (mESCs) on printed arrays of GFs. Hepatocyte

Revzin, Alexander

423

Neural Stem Cell Niches: Critical Roles for the Hyaluronan-Based Extracellular Matrix in Neural Stem Cell Proliferation and Differentiation  

PubMed Central

Neural stem/progenitor cells capable of differentiating into the neurons and glial cells that populate the mammalian central nervous system (CNS) persist in specific neural stem cell niches that regulate stem cell proliferation, survival and differentiation. There is growing evidence that the extracellular matrix within neural stem cell niches is required for neural stem cell maintenance. Here, we review findings supporting a pivotal role for the glycosaminoglycan hyaluronan (HA) and its transmembrane receptors in neural stem/progenitor cell proliferation, differentiation and maturation. We also outline findings supporting changing roles for HA as cells become committed to distinct lineages in the brain and spinal cord. PMID:21622263

Preston, Marnie; Sherman, Larry S.

2012-01-01

424

Derivation of extraembryonic endoderm stem (XEN) cells from mouse embryos and embryonic stem cells  

PubMed Central

At the time of implantation in the maternal uterus, the mouse blastocyst possesses an inner cell mass comprising two lineages: epiblast (Epi) and primitive endoderm (PrE). Representative stem cells derived from these two cell lineages can be expanded and maintained indefinitely in vitro as either embryonic stem (ES ) or XEN cells, respectively. Here we describe protocols that can be used to establish XEN cell lines. These include the establishment of XEN cells from blastocyst-stage embryos in either standard embryonic or trophoblast stem (TS ) cell culture conditions. We also describe protocols for establishing XEN cells directly from ES cells by either retinoic acid and activin-based conversion or by overexpression of the GATA transcription factor Gata6. XEN cells are a useful model of PrE cells, with which they share gene expression, differentiation potential and lineage restriction. The robust protocols for deriving XEN cells described here can be completed within 2–3 weeks. PMID:23640167

Niakan, Kathy K; Schrode, Nadine; Cho, Lily T Y; Hadjantonakis, Anna-Katerina

2014-01-01

425

Alginate encapsulation and hepatic differentiation of embryonic stem cells  

Microsoft Academic Search

The emergence of cell based clinical technologies has been limited by the need for large cell masses (>1011 cells). Embryonic stem cells are a promising solution to this cell source limitation because they are highly proliferative, renewable and pluripotent. Although many investigators have described techniques to effectively differentiate stem cells into a variety of mature cell lineages, these fall short

T. J. Maguire; E. I. Novik; R. Schloss; M. L. Yarmush

2005-01-01

426

Shh signaling regulates adrenocortical development and identifies progenitors of steroidogenic lineages  

PubMed Central

The adrenal cortex is a critical steroidogenic endocrine tissue, generated at least in part from the coelomic epithelium of the urogenital ridge. Neither the intercellular signals that regulate cortical development and maintenance nor the lineage relationships within the adrenal are well defined. We have explored adrenal Shh activity and found that Shh is expressed in relatively undifferentiated steroidogenic cells, which signal to the overlying capsule and subjacent nonsteroidogenic mesenchyme cells that we also find are progenitors of steroidogenic lineages. Shh-expressing cells also generate all steroidogenic cell types, but not nonsteroidogenic ones. Shh mutant adrenals have a thin capsule and small cortex. Our findings both support a novel dual lineage, Shh-independent and Shh-dependent, model of adrenocortical development, and identify distinct populations of adrenocortical progenitor and candidate stem cells. PMID:19955443

King, Peter; Paul, Alex; Laufer, Ed

2009-01-01

427

Last updated 8/1/2008 Genus List for Holtz (2008) Dinosaurs 1 Primitive Dinosauromorphs--the Dinosaurs' Closest Relatives (Chapter 11)  

E-print Network

Last updated 8/1/2008 Genus List for Holtz (2008) Dinosaurs 1 Primitive Dinosauromorphs away: a sort of "negative fossil." Scleromochlus hard fulcrum Late Triassic (216.5-203.6 MYA) 8 in (20 Triassic (228-216.5 MYA) 2.6 ft (80 cm) Chicken New Mexico Very similar to Argentina's Lagerpeton

Holtz Jr., Thomas R.

428

Last updated 1/28/11 Genus List for Holtz (2007) Dinosaurs 1 Primitive Dinosauromorphs--Dinosaurs' Closest Relatives (Chapter 11)  

E-print Network

Last updated 1/28/11 Genus List for Holtz (2007) Dinosaurs 1 Primitive Dinosauromorphs left in the rock where its bones had dissolved away: a sort of "negative fossil." Scleromochlus hard Triassic (228-216.5 MYA) 2.6 ft (80 cm) Chicken Arizona, New Mexico, Texas Very similar to Argentina

Holtz Jr., Thomas R.

429

Diversification of Two Lineages of Symbiotic Photobacterium  

PubMed Central

Understanding of processes driving bacterial speciation requires examination of closely related, recently diversified lineages. To gain an insight into diversification of bacteria, we conducted comparative genomic analysis of two lineages of bioluminescent symbionts, Photobacterium leiognathi and ‘P. mandapamensis’. The two lineages are evolutionary and ecologically closely related. Based on the methods used in bacterial taxonomy for classification of new species (DNA-DNA hybridization and ANI), genetic relatedness of the two lineages is at a cut-off point for species delineation. In this study, we obtained the whole genome sequence of a representative P. leiognathi strain lrivu.4.1, and compared it to the whole genome sequence of ‘P. mandapamensis’ svers.1.1. Results of the comparative genomic analysis suggest that P. leiognathi has a more plastic genome and acquired genes horizontally more frequently than ‘P. mandapamensis’. We predict that different rates of recombination and gene acquisition contributed to diversification of the two lineages. Analysis of lineage-specific sequences in 25 strains of P. leiognathi and ‘P. mandapamensis’ found no evidence that bioluminescent symbioses with specific host animals have played a role in diversification of the two lineages. PMID:24349398

Urbanczyk, Henryk; Urbanczyk, Yoshiko; Hayashi, Tetsuya; Ogura, Yoshitoshi

2013-01-01

430

Lineage fusion in Galápagos giant tortoises.  

PubMed

Although many classic radiations on islands are thought to be the result of repeated lineage splitting, the role of past fusion is rarely known because during these events, purebreds are rapidly replaced by a swarm of admixed individuals. Here, we capture lineage fusion in action in a Galápagos giant tortoise species, Chelonoidis becki, from Wolf Volcano (Isabela Island). The long generation time of Galápagos tortoises and dense sampling (841 individuals) of genetic and demographic data were integral in detecting and characterizing this phenomenon. In C. becki, we identified two genetically distinct, morphologically cryptic lineages. Historical reconstructions show that they colonized Wolf Volcano from Santiago Island in two temporally separated events, the first estimated to have occurred ~199 000 years ago. Following arrival of the second wave of colonists, both lineages coexisted for approximately ~53 000 years. Within that time, they began fusing back together, as microsatellite data reveal widespread introgressive hybridization. Interestingly, greater mate selectivity seems to be exhibited by purebred females of one of the lineages. Forward-in-time simulations predict rapid extinction of the early arriving lineage. This study provides a rare example of reticulate evolution in action and underscores the power of population genetics for understanding the past, present and future consequences of evolutionary phenomena associated with lineage fusion. PMID:25223395

Garrick, Ryan C; Benavides, Edgar; Russello, Michael A; Hyseni, Chaz; Edwards, Danielle L; Gibbs, James P; Tapia, Washington; Ciofi, Claudio; Caccone, Adalgisa

2014-11-01

431

Establishing Clonal Cell Lines with Endothelial-Like Potential from CD9hi, SSEA-1- Cells in Embryonic Stem Cell-Derived Embryoid Bodies  

Microsoft Academic Search

BackgroundDifferentiation of embryonic stem cells (ESCs) into specific cell types with minimal risk of teratoma formation could be efficiently directed by first reducing the differentiation potential of ESCs through the generation of clonal, self-renewing lineage-restricted stem cell lines. Efforts to isolate these stem cells are, however, mired in an impasse where the lack of purified lineage-restricted stem cells has hindered

Qizhou Lian; Kengsuan Yeo; Jianwen Que; Eileenkhiaway Tan; Fenggang Yu; Yijun Yin; Manuel Salto-Tellez; Reida Mensh