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1

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, Nicolás E.; Carrano, Matthew T.; Mannion, Philip D.; Sullivan, Corwin; Upchurch, Paul; Evans, David C.

2014-01-01

2

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

3

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

4

Matrix elasticity directs stem cell lineage specification  

Microsoft Academic Search

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

Dennis Discher

2010-01-01

5

Dinosaurs  

NSDL National Science Digital Library

This video segment from IdahoPTV's D4K shows us what paleontologists think dinosaurs looked like, what they ate, and why they might have disappeared. We see paleontologists at work studying dinosaurs fossils.

Idaho PTV

2011-09-21

6

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

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

Cytoskeleton-based forecasting of stem cell lineage fates  

E-print Network

for stem cell tissue regeneration. During the process of lineage commitment, cells undergo a numberCytoskeleton-based forecasting of stem cell lineage fates Matthew D. Treisera , Eric H. Yanga, and approved November 13, 2009 (received for review August 24, 2009) Stem cells that adopt distinct lineages

Androulakis, Ioannis (Yannis)

9

Dinosaurs  

NSDL National Science Digital Library

On this site students will find three separate website, all with lots of information. Students will then be asked to answer the questions after reviewing the website. First is Dino Data, this website contains the names, classifications, and time line of all dinosaurs. Dino Data 1) What was the time line of dinosaurs, and why did they become extinct. 2) What was the most interesting Dino Data you found? The next website was chosen for it's wonderful description of dinosaur names. Dino Names: Why they are named and why 1) What ...

Morton, Mr.

2010-09-27

10

Dinosaur  

NSDL National Science Digital Library

This is a series of experiments about dinosaurs and paleontology that was designed for use in the second grade. Each activity gives the needed materials, what to do, and what to think about. All are designed so the student uses everyday, inexpensive materials and they reinforce information that has already been taught. The Teacher's Notes provide the purpose of the activity, preparation, and notes.

Candelora, D. M.; Program, The H.

2007-12-12

11

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

12

Researcharticle Molecular Signatures of the Three Stem Cell Lineages in  

E-print Network

Researcharticle Molecular Signatures of the Three Stem Cell Lineages in Hydra and the Emergence of Stem Cell Function at the Base of Multicellularity Georg Hemmrich,y,1 Konstantin Khalturin,y,1 Anna, Zagreb, Croatia 6 Laboratory for Pluripotent Stem Cell Studies, RIKEN Center for Developmental Biology

13

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

14

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

15

Notch Promotes Neural Lineage Entry by Pluripotent Embryonic Stem Cells  

Microsoft Academic Search

A central challenge in embryonic stem (ES) cell biology is to understand how to impose direction on primary lineage commitment. In basal culture conditions, the majority of ES cells convert asynchronously into neural cells. However, many cells resist differentiation and others adopt nonneural fates. Mosaic activation of the neural reporter Sox-green fluorescent protein suggests regulation by cell-cell interactions. We detected

Sally Lowell; Alexandra Benchoua; Barry Heavey; Austin G Smith

2006-01-01

16

Generation of enteroendocrine cell diversity in midgut stem cell lineages.  

PubMed

The endocrine system mediates long-range peptide hormone signaling to broadcast changes in metabolic status to distant target tissues via the circulatory system. In many animals, the diffuse endocrine system of the gut is the largest endocrine tissue, with the full spectrum of endocrine cell subtypes not yet fully characterized. Here, we combine molecular mapping, lineage tracing and genetic analysis in the adult fruit fly to gain new insight into the cellular and molecular mechanisms governing enteroendocrine cell diversity. Neuropeptide hormone distribution was used as a basis to generate a high-resolution cellular map of the diffuse endocrine system. Our studies show that cell diversity is seen at two distinct levels: regional and local. We find that class I and class II enteroendocrine cells can be distinguished locally by combinatorial expression of secreted neuropeptide hormones. Cell lineage tracing studies demonstrate that class I and class II cells arise from a common stem cell lineage and that peptide profiles are a stable feature of enteroendocrine cell identity during homeostasis and following challenge with the enteric pathogen Pseudomonas entomophila. Genetic analysis shows that Notch signaling controls the establishment of class II cells in the lineage, but is insufficient to reprogram extant class I cells into class II enteroendocrine cells. Thus, one mechanism by which secretory cell diversity is achieved in the diffuse endocrine system is through cell-cell signaling interactions within individual adult stem cell lineages. PMID:25670792

Beehler-Evans, Ryan; Micchelli, Craig A

2015-02-15

17

Reduced lymphoid lineage priming promotes human hematopoietic stem cell expansion.  

PubMed

The hematopoietic system sustains regeneration throughout life by balancing self-renewal and differentiation. To stay poised for mature blood production, hematopoietic stem cells (HSCs) maintain low-level expression of lineage-associated genes, a process termed lineage priming. Here, we modulated expression levels of Inhibitor of DNA binding (ID) proteins to ask whether lineage priming affects self-renewal of human HSCs. We found that lentiviral overexpression of ID proteins in cord blood HSCs biases myeloerythroid commitment at the expense of lymphoid differentiation. Conversely, reducing ID2 expression levels increases lymphoid potential. Mechanistically, ID2 inhibits the transcription factor E47 to attenuate B-lymphoid priming in HSCs and progenitors. Strikingly, ID2 overexpression also results in a 10-fold expansion of HSCs in serial limiting dilution assays, indicating that early lymphoid transcription factors antagonize human HSC self-renewal. The relationship between lineage priming and self-renewal can be exploited to increase expansion of transplantable human HSCs and points to broader implications for other stem cell populations. PMID:24388174

van Galen, Peter; Kreso, Antonija; Wienholds, Erno; Laurenti, Elisa; Eppert, Kolja; Lechman, Eric R; Mbong, Nathan; Hermans, Karin; Dobson, Stephanie; April, Craig; Fan, Jian-Bing; Dick, John E

2014-01-01

18

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

19

Lineage tracing quantification reveals symmetric stem cell division in Drosophila male germline stem cells  

PubMed Central

Summary In the homeostatic state, adult stem cells divide either symmetrically to increase the stem cell number to compensate stem cell loss, or asymmetrically to maintain the population while producing differentiated cells. We have investigated the mode of stem cell division in the testes of Drosophila melanogaster by lineage tracing and confirm the presence of symmetric stem cell division in this system. We found that the rate of symmetric division is limited to 1-2% of total germline stem cell (GSC) divisions, but it increases with expression of a cell adhesion molecule, E-cadherin, or a regulator of the actin cytoskeleton, Moesin, which may modulate adhesiveness of germ cells to the stem cell niche. Our results indicate that the decision regarding asymmetric vs. symmetric division is a dynamically regulated process that contributes to tissue homeostasis, responding to the needs of the tissue. PMID:24465278

Salzmann, Viktoria; Inaba, Mayu; Cheng, Jun; Yamashita, Yukiko M.

2014-01-01

20

Slit/Robo signaling regulates cell fate decisions in the intestinal stem cell lineage of Drosophila.  

PubMed

In order to maintain tissue homeostasis, cell fate decisions within stem cell lineages have to respond to the needs of the tissue. This coordination of lineage choices with regenerative demand remains poorly characterized. Here, we identify a signal from enteroendocrine cells (EEs) that controls lineage specification in the Drosophila intestine. We find that EEs secrete Slit, a ligand for the Robo2 receptor in intestinal stem cells (ISCs) that limits ISC commitment to the endocrine lineage, establishing negative feedback control of EE regeneration. Furthermore, we show that this lineage decision is made within ISCs and requires induction of the transcription factor Prospero in ISCs. Our work identifies a function for the conserved Slit/Robo pathway in the regulation of adult stem cells, establishing negative feedback control of ISC lineage specification as a critical strategy to preserve tissue homeostasis. Our results further amend the current understanding of cell fate commitment within the Drosophila ISC lineage. PMID:24931602

Biteau, Benoît; Jasper, Heinrich

2014-06-26

21

Dermal Stem Cells Can Differentiate Down an Endothelial Lineage  

PubMed Central

In this study, we have demonstrated that cells of neural crest origin located in the dermal papilla (DP) exhibit endothelial marker expression and a functional activity. When grown in endothelial growth media, DP primary cultures upregulate expression of vascular endothelial growth factor receptor 1 (FLT1) mRNA and downregulate expression of the dermal stem cell marker ?-smooth muscle actin. DP cells have demonstrated functional characteristics of endothelial cells, including the ability to form capillary-like structures on Matrigel, increase uptake of low-density lipoprotein and upregulate ICAM1 (CD54) in response to tumour necrosis factor alpha (TNF-?) stimulation. We confirmed that these observations were not due to contaminating endothelial cells, by using DP clones. We have also used the WNT1cre/ROSA26R and WNT1cre/YFP lineage-tracing mouse models to identify a population of neural crest-derived cells in DP cultures that express the endothelial marker PECAM (CD31); these cells also form capillary-like structures on Matrigel. Importantly, cells of neural crest origin that express markers of endothelial and mesenchymal lineages exist within the dermal sheath of the vibrissae follicle. PMID:22571645

Bell, Emma; Richardson, Gavin D.; Jahoda, Colin A.; Gledhill, Karl; Phillips, Helen M.; Henderson, Deborah; Owens, W. Andrew

2012-01-01

22

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

23

Lineage specification of hematopoietic stem cells: mathematical modeling and biological implications.  

PubMed

Lineage specification of hematopoietic stem cells is considered a progressive restriction in lineage potential. This view is consistent with observations that differentiation and lineage specification is preceded by a low-level coexpression of lineage specific, potentially antagonistic genes in early progenitor cells. This coexistence, commonly referred to as priming, disappears in the course of differentiation when certain lineage-restricted genes are upregulated while others are downregulated. Based on this phenomenological description, we propose a quantitative model that describes lineage specification as a competition process between different interacting lineage propensities. The competition is governed by environmental stimuli promoting a drift from a multipotent coexpression to the dominance of one lineage. The assumption of a context-dependent intracellular differentiation control is consistently embedded into our previously proposed model of hematopoietic stem cell organization. The extended model, which comprises self-renewal and lineage specification, is verified using available data on the lineage specification potential of primary hematopoietic stem cells and on the differentiation kinetics of the FDCP-mix cell line. The model provides a number of experimentally testable predictions. From our results, we conclude that lineage specification is best described as a flexible and temporally extended process in which lineage commitment emerges as the result of a sequence of small decision steps. The proposed model provides a novel systems biological view on the functioning of lineage specification in adult tissue stem cells and its connections to the self-renewal properties of these cells. Disclosure of potential conflicts of interest is found at the end of this article. PMID:17412891

Glauche, Ingmar; Cross, Michael; Loeffler, Markus; Roeder, Ingo

2007-07-01

24

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

25

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

26

Tawa hallae - Dinosaur Ancient History  

NSDL National Science Digital Library

When paleontologists unearthed the ancient dinosaur Tawa hallae, they knew it was different--and remarkably well preserved. What they did not know is that the animal has an intriguing lineage, one that answers questions about the earliest evolution of dinosaurs.

27

Origins of adult pigmentation: diversity in pigment stem cell lineages and implications for pattern evolution.  

PubMed

Teleosts comprise about half of all vertebrate species and exhibit an extraordinary diversity of adult pigment patterns that function in shoaling, camouflage, and mate choice and have played important roles in speciation. Here, we review studies that have identified several distinct neural crest lineages, with distinct genetic requirements, that give rise to adult pigment cells in fishes. These lineages include post-embryonic, peripheral nerve-associated stem cells that generate black melanophores and iridescent iridophores, cells derived directly from embryonic neural crest cells that generate yellow-orange xanthophores, and bipotent stem cells that generate both melanophores and xanthophores. This complexity in adult chromatophore lineages has implications for our understanding of adult traits, melanoma, and the evolutionary diversification of pigment cell lineages and patterns. PMID:25421288

Parichy, David M; Spiewak, Jessica E

2015-01-01

28

Independent stem cell lineages regulate adipose organogenesis and adipose homeostasis  

PubMed Central

Summary Adipose tissues have striking plasticity, highlighted by childhood and adult obesity. Using adipose lineage analyses, smooth muscle actin (SMA)-mural cell fate mapping, and conditional PPAR? deletion to block adipocyte differentiation, we find two phases of adipocyte generation that emanate from two independent adipose progenitor compartments, Developmental and Adult. These two compartments are sequentially required for organ formation and maintenance. Although both Developmental and Adult progenitors are specified during the developmental period and express PPAR?, they have distinct micro-anatomical, functional, morphogenetic and molecular profiles. Further, the two compartments derive from different lineages, while adult adipose progenitors fate map from an SMA+ mural lineage, Developmental progenitors do not. Remarkably, the Adult progenitor compartment appears to be specified earlier than the Developmental cells, and then enters the already developmentally formed adipose depots. Thus, two distinct cell compartments control adipose organ development and organ homeostasis, which may provide discrete therapeutic target for childhood and adult obesity. PMID:25437556

Jiang, Yuwei; Berry, Daniel C.; Tang, Wei; Graff, Jonathan M.

2014-01-01

29

Sox2+ Stem Cells Contribute to All Epithelial Lineages of the Tooth via Sfrp5+ Progenitors  

PubMed Central

SUMMARY The continuously growing mouse incisor serves as a valuable model to study stem cell regulation during organ renewal. Epithelial stem cells are localized in the proximal end of the incisor in the labial cervical loop. Here, we show that the transcription factor Sox2 is a specific marker for these stem cells. Sox2+ cells became restricted to the labial cervical loop during tooth morphogenesis, and they contributed to the renewal of enamel-producing ameloblasts as well as all other epithelial cell lineages of the tooth. The early progeny of Sox2-positive stem cells transiently expressed the Wnt inhibitor Sfrp5. Sox2 expression was regulated by the tooth initiation marker FGF8 and specific miRNAs, suggesting a fine-tuning to maintain homeostasis of the dental epithelium. The identification of Sox2 as a marker for the dental epithelial stem cells will facilitate further studies on their lineage segregation and differentiation during tooth renewal. PMID:22819339

Juuri, Emma; Saito, Kan; Ahtiainen, Laura; Seidel, Kerstin; Tummers, Mark; Hochedlinger, Konrad; Klein, Ophir D.; Thesleff, Irma; Michon, Frederic

2012-01-01

30

Reproductive stem cell differentiation: extracellular matrix, tissue microenvironment, and growth factors direct the mesenchymal stem cell lineage commitment.  

PubMed

The mesenchymal stem cells (MSCs) have awakened interest in regenerative medicine due to its high capability to proliferate and differentiate in multiple specialized lineages under defined conditions. The reproductive system is considered a valuable source of MSCs, which needs further investigations. Many factors have been reported as critical for these cell lineage specification and determination. In this review, we discuss the main effects of extracellular matrix or tissue environment and growth factors in the cell lineage commitment, including the reproductive stem cells. The MSCs responses to culture medium stimuli or to soluble factors probably occur through several intracellular activation pathways. However, the molecular mechanisms in which the cells respond to these mechanical or chemical perturbations remain elusive. Recent findings suggest a synergic effect of microenvironment and soluble cell culture factors affecting cell differentiation. For future applications in cell therapy, protocols of reproductive MSCs differentiation must be established. PMID:23420825

Vidane, Atanásio S; Zomer, Helena D; Oliveira, Bruna M M; Guimarães, Carina F; Fernandes, Cláudia B; Perecin, Felipe; Silva, Luciano A; Miglino, Maria A; Meirelles, Flávio V; Ambrósio, Carlos E

2013-10-01

31

Dinosaur Day!  

ERIC Educational Resources Information Center

In this article, the authors describe how they capitalized on their first-grade students' love of dinosaurs by hosting a fun-filled Dinosaur Day in their classroom. On Dinosaur Day, 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…

Nakamura, Sandra; Baptiste, H. Prentice

2006-01-01

32

Modeling spatial population dynamics of stem cell lineage in wound healing and cancerogenesis  

E-print Network

Modeling spatial population dynamics of stem cell lineage in wound healing and cancerogenesis study the effects of different strengths of wound signals to wound healing behaviors. We also study the correlations between chronic wound and cancerogenesis. I. INTRODUCTION Wound healing is a complex process

Dai, Yang

33

Stem cells, progenitor cells, and lineage decisions in the ovary.  

PubMed

Exploring stem cells in the mammalian ovary has unleashed a Pandora's box of new insights and questions. Recent evidence supports the existence of stem cells of a number of the different cell types within the ovary. The evidence for a stem cell model producing mural granulosa cells and cumulus cells is strong, despite a limited number of reports. The recent identification of a precursor granulosa cell, the gonadal ridge epithelial-like cell, is exciting and novel. The identification of female germline (oogonial) stem cells is still very new and is currently limited to just a few species. Their origins and physiological roles, if any, are unknown, and their potential to produce oocytes and contribute to follicle formation in vivo lacks robust evidence. The precursor of thecal cells remains elusive, and more compelling data are needed. Similarly, claims of very small embryonic-like cells are also preliminary. Surface epithelial cells originating from gonadal ridge epithelial-like cells and from the mesonephric epithelium at the hilum of the ovary have also been proposed. Another important issue is the role of the stroma in guiding the formation of the ovary, ovigerous cords, follicles, and surface epithelium. Immune cells may also play key roles in developmental patterning, given their critical roles in corpora lutea formation and regression. Thus, while the cellular biology of the ovary is extremely important for its major endocrine and fertility roles, there is much still to be discovered. This review draws together the current evidence and perspectives on this topic. PMID:25541635

Hummitzsch, Katja; Anderson, Richard A; Wilhelm, Dagmar; Wu, Ji; Telfer, Evelyn E; Russell, Darryl L; Robertson, Sarah A; Rodgers, Raymond J

2015-02-01

34

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

35

FGF signalling as a mediator of lineage transitions--evidence from embryonic stem cell differentiation.  

PubMed

The fibroblast growth factor (FGF) signalling pathway is one of the most ubiquitous in biology. It has diverse roles in development, differentiation and cancer. Embryonic stem (ES) cells are in vitro cell lines capable of differentiating into all the lineages of the conceptus. As such they have the capacity to differentiate into derivatives of all three germ layers and to some extent the extra-embryonic lineages as well. Given the prominent role of FGF signalling in early embryonic development, we explore the role of this pathway in early ES cell differentiation towards the major lineages of the embryo. As early embryonic differentiation is intricately choreographed at the level of morphogenetic movement, adherent ES cell culture affords a unique opportunity to study the basic steps in early lineage specification in the absence of ever shifting complex in vivo microenvironments. Thus recent experiments in ES cell differentiation are able to pinpoint specific FGF dependent lineage transitions that are difficult to resolve in vivo. Here we review the role of FGF signalling in early development alongside the ES cell data and suggest that FGF dependent signalling via phospho-Erk activation maybe a major mediator of transitions in lineage specification. PMID:20336694

Villegas, Santiago Nahuel; Canham, Maurice; Brickman, Joshua M

2010-05-01

36

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

37

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.

38

Polycomb group protein expression during differentiation of human embryonic stem cells into pancreatic lineage in vitro  

PubMed Central

Background Polycomb Group (PcG) proteins are chromatin modifiers involved in early embryonic development as well as in proliferation of adult stem cells and cancer cells. PcG proteins form large repressive complexes termed Polycomb Repressive Complexes (PRCs) of which PRC1 and PRC2 are well studied. Differentiation of human Embryonic Stem (hES) cells into insulin producing cells has been achieved to limited extent, but several aspects of differentiation remain unexplored. The PcG protein dynamics in human embryonic stem (hES) cells during differentiation into pancreatic lineage has not yet been reported. In the present study, the expression of RING1A, RING1B, BMI1, CBX2, SUZ12, EZH2, EED and JARID2 during differentiation of hES cells towards pancreatic lineage was examined. Results In-house derived hES cell line KIND1 was used to study expression of PcG protein upon spontaneous and directed differentiation towards pancreatic lineage. qRT-PCR analysis showed expression of gene transcripts for various lineages in spontaneously differentiated KIND1 cells, but no differentiation into pancreatic lineage was observed. Directed differentiation induced KIND1 cells grown under feeder-free conditions to transition from definitive endoderm (Day 4), primitive gut tube stage (Day 8) and pancreatic progenitors (Day 12-Day 16) as evident from expression of SOX17, PDX1 and SOX9 by qRT-PCR and Western blotting. In spontaneously differentiating KIND1 cells, RING1A and SUZ12 were upregulated at day 15, while other PcG transcripts were downregulated. qRT-PCR analysis showed transcripts of RING1B, BMI1, SUZ12, EZH2 and EED were upregulated, while RING1A and CBX2 expression remained low and JARID2 was downregulated during directed differentiation of KIND1 cells. Upregulation of BMI1, EZH2 and SUZ12 during differentiation into pancreatic lineage was also confirmed by Western blotting. Histone modifications such as H3K27 trimethylation and monoubiquitinylation of H2AK119 increased during differentiation into pancreatic lineage as seen by Western blotting. Conclusion Our study shows expression of PcG proteins was distinct during spontaneous and directed differentiation. Differentiation into pancreatic lineage was achieved by directed differentiation approach and was associated with increased expression of PcG proteins RING1B, BMI1, EZH2 and SUZ12 accompanied by increase in monoubiquitinylation of H2AK119 and trimethylation of H3K27. PMID:24885493

2014-01-01

39

Dinosaur Interaction  

NSDL National Science Digital Library

In this activity, learners explore why animals, specifically dinosaurs, live in families. Learners examine Dinosphere scenes (drawing of dinosaurs in groups) and sort the scenes by reasons the animals are living in groups. Then, learners glue together geometric shapes to create dinosaurs interacting in groups and families. This activity is featured on page 26 of the "Dinosphere" unit of study for K-2 learners.

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

2004-01-01

40

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.

41

The Dinosaur Database  

NSDL National Science Digital Library

This database contains detailed information on hundreds of dinosaurs and dinosaur related topics. It features a dinosaur dictionary, dinosaur clip art and flex-art, and links to lesson plans and dinosaur experiments for teachers.

42

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

43

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

44

Constitutive Notch2 signaling in neural stem cells promotes tumorigenic features and astroglial lineage entry  

PubMed Central

Recent studies identified a highly tumorigenic subpopulation of glioma stem cells (GSCs) within malignant gliomas. GSCs are proposed to originate from transformed neural stem cells (NSCs). Several pathways active in NSCs, including the Notch pathway, were shown to promote proliferation and tumorigenesis in GSCs. Notch2 is highly expressed in glioblastoma multiforme (GBM), a highly malignant astrocytoma. It is therefore conceivable that increased Notch2 signaling in NSCs contributes to the formation of GBM. Here, we demonstrate that mice constitutively expressing the activated intracellular domain of Notch2 in NSCs display a hyperplasia of the neurogenic niche and reduced neuronal lineage entry. Neurospheres derived from these mice show increased proliferation, survival and resistance to apoptosis. Moreover, they preferentially differentiate into astrocytes, which are the characteristic cellular population of astrocytoma. Likewise, we show that Notch2 signaling increases proliferation and resistance to apoptosis in human GBM cell lines. Gene expression profiling of GBM patient tumor samples reveals a positive correlation of Notch2 transcripts with gene transcripts controlling anti-apoptotic processes, stemness and astrocyte fate, and a negative correlation with gene transcripts controlling proapoptotic processes and oligodendrocyte fate. Our data show that Notch2 signaling in NSCs produces features of GSCs and induces astrocytic lineage entry, consistent with a possible role in astrocytoma formation. PMID:22717580

Tchorz, J S; Tome, M; Cloëtta, D; Sivasankaran, B; Grzmil, M; Huber, R M; Rutz-Schatzmann, F; Kirchhoff, F; Schaeren-Wiemers, N; Gassmann, M; Hemmings, B A; Merlo, A; Bettler, B

2012-01-01

45

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

46

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

47

Dinosaur News  

NSDL National Science Digital Library

Publishing the latest findings and theories in the wide world of dinosaur science since 1998, Dinosaur News will raise the eyebrows of even the least paleontologically inclined. Did you know that tyrannosauruses may have hunted in packs? Are you curious where the apocalyptic asteroid that wiped out the dinosaurs came from? Want to hear about the latest dinosaur exhibits from around the country â and the world? The Dinosaur News has all this and more. Visitors can explore a variety of features, including Links We Like and What Readers Say, but may wish to start with The Dinosaurnews Daily. This newsfeed-style site is updated daily and offers exciting headlines, photos, videos, and more. Make sure to sign up for the Dinosaur News Newsletter, then tour the well-appointed bookstore and the gift shop if so desired.

48

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_.

49

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

50

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

51

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.

52

Dinosaur Detectives  

NSDL National Science Digital Library

This lesson plan will help students learn that discoveries about dinosaurs have a long history and that each paleontologist adds his or her work to a body of fossil evidence used to support theories about dinosaurs. In it, students will use the internet to explore the discovery of fossils and dinosaurs. The website includes the lesson plan, extensions, guidelines for evaluation, and MCREL standards alignment.

Carangelo, Audrey

2008-01-01

53

Zoom Dinosaurs  

NSDL National Science Digital Library

This colorful, informative and cluttered site is "a comprehensive on-line hypertext book about dinosaurs" by Enchanted Learning Software. Designed for students "of all ages and levels of comprehension," Zoom Dinosaurs is most appropriate for the K-12 level. Topics are presented at a basic level (e.g., All About Dinosaurs, Anatomy & Behavior, Mesozoic Era), but by clicking on hyperlinked text, users may progress to more advanced information. Classroom activities include dinosaur-related word games, quizzes, art projects, and fossil record/geologic timeline activities. A selection of links connects curious users to additional K-12 educational sites.

54

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

55

Cytokine-regulated GADD45G induces differentiation and lineage selection in hematopoietic stem cells.  

PubMed

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

2014-07-01

56

Sequential changes at differentiation gene promoters as they become active in a stem cell lineage.  

PubMed

Transcriptional silencing of terminal differentiation genes by the Polycomb group (PcG) machinery is emerging as a key feature of precursor cells in stem cell lineages. How, then, is this epigenetic silencing reversed for proper cellular differentiation? Here, we investigate how the developmental program reverses local PcG action to allow expression of terminal differentiation genes in the Drosophila male germline stem cell (GSC) lineage. We find that the silenced state, set up in precursor cells, is relieved through developmentally regulated sequential events at promoters once cells commit to spermatocyte differentiation. The programmed events include global downregulation of Polycomb repressive complex 2 (PRC2) components, recruitment of hypophosphorylated RNA polymerase II (Pol II) to promoters, as well as the expression and action of testis-specific homologs of TATA-binding protein-associated factors (tTAFs). In addition, action of the testis-specific meiotic arrest complex (tMAC), a tissue-specific version of the MIP/dREAM complex, is required both for recruitment of tTAFs to target differentiation genes and for proper cell type-specific localization of PRC1 components and tTAFs within the spermatocyte nucleolus. Together, the action of the tMAC and tTAF cell type-specific chromatin and transcription machinery leads to loss of Polycomb and release of stalled Pol II from the terminal differentiation gene promoters, allowing robust transcription. PMID:21610025

Chen, Xin; Lu, Chenggang; Morillo Prado, Jose Rafael; Eun, Suk Ho; Fuller, Margaret T

2011-06-01

57

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

58

Dinosaur Dig  

NSDL National Science Digital Library

4th Grade Fossils Unit Your mission is to write a story about a dinosaur that lived and died in Utah. Include in your story what kind of dinosaur your story is about, where it lived, how it lived, what it ate, how it died, and how it became fossilized. Find or draw ...

Vincent, Teanna

2009-11-09

59

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

60

Dinosaur Names  

NSDL National Science Digital Library

In this activity, students will appreciate how descriptive dinosaur names are formed. They will use multiple combining forms added to the suffix "-saurus" (Greek for lizard) to form the name of a "dinosaur" which they will then draw. This activity contains background information, materials, directions, and extension activities.

Craig Munsart

61

Dinosaur Homes  

NSDL National Science Digital Library

In this activity about dinosaurs and survival, learners use scrap materials to create a miniature dinosaur habitat that includes a food source, water source, and shelter. This resource includes definitions of key words (habitat, carnivores, herbivores, omnivores, extinct) as well as discussion questions to further learning.

Omsi

2004-01-01

62

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.

63

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

PubMed

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 progenitors, 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 instruction, the initiation of HSC commitment is generally thought to be triggered by stochastic fluctuation in cell-intrinsic regulators such as lineage-specific transcription factors, leaving cytokines to ensure survival and proliferation of the progeny cells. 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

2013-05-01

64

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

65

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

66

Axes of differentiation in breast cancer: untangling stemness, lineage identity, and the epithelial to mesenchymal transition.  

PubMed

Differentiation-associated regulatory programs are central in determining tumor phenotype, and contribute to heterogeneity between tumors and between individual cells within them. The transcriptional programs that control luminal and basal lineage identity in the normal mammary epithelium, as well as progenitor and stem cell function, are active in breast cancers, and show distinct associations with different disease subtypes. Also active in some tumors is the epithelial to mesenchymal transition (EMT) program, which endows carcinoma cells with mesenchymal as well as stem cell traits. The differentiation state of breast cancer cells is thus dictated by the complex combination of regulatory programs, and these can dramatically affect tumor growth and metastatic capacity. Breast cancer differentiation is often viewed along an axis between a basal–mesenchymal–stem cell state and a luminal–epithelial–differentiated state. Here we consider the links, as well as the distinctions, between the three components of this axis: basal versus luminal, mesenchymal versus epithelial, and stem cell versus differentiated identity. Analysis on a multidimensional scale, in which each of these axes is assessed separately, may offer increased resolution of tumor differentiation state. Cancer cells possessing a high degree of stemness would display increased capacity to shift between positions on such a multidimensional scale, and to acquire intermediate phenotypes on its different axes. Further molecular analysis of breast cancer cells with a focus on single-cell profiling, and the development of improved tools for dissection of the circuits controlling gene activity, are essential for the elucidation of the programs dictating breast cancer differentiation state. PMID:24741710

Granit, Roy Z; Slyper, Michal; Ben-Porath, Ittai

2014-01-01

67

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

68

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.

69

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

70

Small Molecules Greatly Improve Conversion of Human-Induced Pluripotent Stem Cells to the Neuronal Lineage  

PubMed Central

Efficient in vitro differentiation into specific cell types is more important than ever after the breakthrough in nuclear reprogramming of somatic cells and its potential for disease modeling and drug screening. Key success factors for neuronal differentiation are the yield of desired neuronal marker expression, reproducibility, length, and cost. Three main neuronal differentiation approaches are stromal-induced neuronal differentiation, embryoid body (EB) differentiation, and direct neuronal differentiation. Here, we describe our neurodifferentiation protocol using small molecules that very efficiently promote neural induction in a 5-stage EB protocol from six induced pluripotent stem cells (iPSC) lines from patients with Parkinson's disease and controls. This protocol generates neural precursors using Dorsomorphin and SB431542 and further maturation into dopaminergic neurons by replacing sonic hedgehog with purmorphamine or smoothened agonist. The advantage of this approach is that all patient-specific iPSC lines tested in this study were successfully and consistently coaxed into the neural lineage. PMID:22567022

Mak, Sally K.; Huang, Y. Anne; Iranmanesh, Shifteh; Vangipuram, Malini; Sundararajan, Ramya; Nguyen, Loan; Langston, J. William; Schüle, Birgitt

2012-01-01

71

Lineage-specific regulation of imprinted X inactivation in extraembryonic endoderm stem cells  

PubMed Central

Background Silencing of the paternal X chromosome (Xp), a phenomenon known as imprinted X-chromosome inactivation (I-XCI), characterises, amongst mouse extraembryonic lineages, the primitive endoderm and the extraembryonic endoderm (XEN) stem cells derived from it. Results Using a combination of chromatin immunoprecipitation characterisation of histone modifications and single-cell expression studies, we show that whilst the Xp in XEN cells, like the inactive X chromosome in other cell types, globally accumulates the repressive histone mark H3K27me3, a large number of Xp genes locally lack H3K27me3 and escape from I-XCI. In most cases this escape is specific to the XEN cell lineage. Importantly, the degree of escape and the genes concerned remain unchanged upon XEN conversion into visceral endoderm, suggesting stringent control of I-XCI in XEN derivatives. Surprisingly, chemical inhibition of EZH2, a member of the Polycomb repressive complex 2 (PRC2), and subsequent loss of H3K27me3 on the Xp, do not drastically perturb the pattern of silencing of Xp genes in XEN cells. Conclusions The observations that we report here suggest that the maintenance of gene expression profiles of the inactive Xp in XEN cells involves a tissue-specific mechanism that acts partly independently of PRC2 catalytic activity. PMID:25053977

2014-01-01

72

Germline stem cell lineage tracing by free-floating immunofluorescent assay of mouse seminiferous tubule.  

PubMed

Whole-mount immunohistochemistry (whole-mount IH) of the seminiferous tubule is widely used to investigate the self-renewal and differentiation of spermatogonial stem cells (SSCs). Examination of the length of spermatogonial cysts is critical for tracing SSCs lineage by using Whole-mount IH. However, it is difficult for antibody molecules to penetrate into the depth of seminiferous epithelium because its thickness and the tight peritubular myoid and basement membrane outside. Here, we developed a free-floating immunofluorescent procedure of mouse seminiferous tubules using regular incubation time and normal antibody concentration. Microscopic results showed that undifferentiated spermatogonia were positively labeled by promyelocytic leukemia zinc finger protein, E-cadherin, and glial cell line-derived neurotrophic factor family receptor alpha 1, respectively. Spermatogonial cysts in varied length were revealed clearly and spermatogonia subpopulations including A(single) (A(s)), A(paired) (A(pr)), and A(aligned) (A(al)) were distinguished in lower background images. This method provides us an alternate simple way to trace the lineage of individual SSCs and show their three-dimensional locations and distributions within their niches anatomically in next step. PMID:22711565

Jin, Bo; Guo, Bin; Che, Guanyu; Sun, Yixue; Liu, Yang; Zhang, Xueming

2012-08-01

73

Mechanical modulation of nascent stem cell lineage commitment in tissue engineering scaffolds.  

PubMed

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 stem 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; Knothe Tate, Melissa L

2013-07-01

74

Dinosaur Predation  

Microsoft Academic Search

\\u000a Carnivorous dinosaurs (Theropoda) such as Tyrannosaurus rex, Velociraptor mongoliensis, and Spinosaurus aegyptiacus are among the most popularly known fossil species and (perhaps together with the felid Smilodon and the synapsid Dimetrodon) represent the public’s primary vision of extinct predators. Numerous restorations of theropods engaged in mortal combat\\u000a with each other or with one of the many clades of herbivorous dinosaurs

75

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

76

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

77

Reactive oxygen species enhance differentiation of human embryonic stem cells into mesendodermal lineage.  

PubMed

Recently, reactive oxygen species (ROS) have been studied as a regulator of differentiation into specific cell types in embryonic stem cells (ESCs). However, ROS role in human ESCs (hESCs) is unknown because mouse ESCs have been used mainly for most studies. Herein we suggest that ROS generation may play a critical role in differentiation of hESCs; ROS enhances differentiation of hESCs into bi-potent mesendodermal cell lineage via ROS-involved signaling pathways. In ROS-inducing conditions, expression of pluripotency markers (Oct4, Tra 1-60, Nanog, and Sox2) of hESCs was decreased, while expression of mesodermal and endodermal markers was increased. Moreover, these differentiation events of hESCs in ROS-inducing conditions were decreased by free radical scavenger treatment. hESC-derived embryoid bodies (EBs) also showed similar differentiation patterns by ROS induction. In ROS-related signaling pathway, some of the MAPKs family members in hESCs were also affected by ROS induction. p38 MAPK and AKT (protein kinases B, PKB) were inactivated significantly by buthionine sulfoximine (BSO) treatment. JNK and ERK phosphorylation levels were increased at early time of BSO treatment but not at late time point. Moreover, MAPKs family-specific inhibitors could prevent the mesendodermal differentiation of hESCs by ROS induction. Our results demonstrate that stemness and differentiation of hESCs can be regulated by environmental factors such as ROS. PMID:20164681

Ji, Ae-Ri; Ku, Seung-Yup; Cho, Myung Soo; Kim, Yoon Young; Kim, Yong Jin; Oh, Sun Kyung; Kim, Seok Hyun; Moon, Shin Yong; Choi, Young Min

2010-03-31

78

Fam40b is required for lineage commitment of murine embryonic stem cells  

PubMed Central

FAM40B (STRIP2) is a member of the striatin-interacting phosphatase and kinase (STRIPAK) complex that is involved in the regulation of various processes such as cell proliferation and differentiation. Its role for differentiation processes in embryonic stem cells (ESCs) is till now completely unknown. Short hairpin RNA (shRNA)-mediated silencing of Fam40b expression in ESCs and differentiating embryoid bodies (EBs) led to perturbed differentiation to embryonic germ layers and their derivatives including a complete abrogation of cardiomyogenesis. Pluripotency factors such as Nanog, Oct4 and Sox2 as well as epigenetic factors such as histone acetyltransferase type B (HAT1) and DNA (cytosine-5)-methyltransferase 3-? (Dnmt3b) were highly upregulated in Fam40b knockdown EBs as compared with control and scrambled EBs. To examine the relevance of Fam40b for development in vivo, Fam40b was knocked down in developing zebrafish. Morpholino-mediated knockdown of Fam40b led to severe abnormalities of the cardiovascular system, including an impaired expression of ventricular myosin heavy chain (vmhc) and of cardiac myosin light chain 2 (cmlc2) in the heart. We identified the gene product of Fam40b in ESCs as a perinuclear and nucleolar protein with a molecular weight of 96?kDa. We conclude that the expression of Fam40b is essential for the lineage commitment of murine embryonic stem cells (mESCs) into differentiated somatic cells via mechanisms involving pluripotency and epigenetic networks. PMID:25010986

Wagh, V; Doss, M X; Sabour, D; Niemann, R; Meganathan, K; Jagtap, S; Gaspar, J A; Ardestani, M A; Papadopoulos, S; Gajewski, M; Winkler, J; Hescheler, J; Sachinidis, A

2014-01-01

79

Dinosaurs 1: Where Are the Dinosaurs ?  

NSDL National Science Digital Library

This Science NetLinks lesson is the first of a two-part series on dinosaurs. This lesson taps into student curiosity about dinosaurs in order to lead them to consider life forms that no longer exist. A variety of activities are suggested, including viewing online video clips, creating dinosaur puppets, and constructing dinosaur eggs.

Science Netlinks;

2003-04-15

80

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

81

Matrix elasticity perturbation and Lamin-A/C expression in stem cells modulate their mechanics and lineage specification  

NASA Astrophysics Data System (ADS)

Commitment of stem cells to different lineages is regulated by many cues in their local microenvironment. They are particularly sensitive to the mechanical properties of their extracellular matrix. Nuclear lamins are fibrous proteins providing structural function and transcriptional regulation in the cell nucleus. In particular Lamin A/C levels could influence cellular mechanical sensitivity. Here we show that perturbation of the extracellular matrix and nucleus mechanics can direct stem cells lineage specification. We studied the behavior of human mensechymal stem cells (hMSC) cultured on thin highly ordered collagen nanofilms. To tune the mechanical properties of the nanofilms we used the enzyme transglutaminase as a crosslinking agent. AFM imaging and manipulation is used to examine the nano topography and mechanical properties of the films and cells. Film stiffening affects cells morphology, cytoskeleton organization and their elastic response. hMSCs cultured for two weeks on collagen nanofilms initially tune their stiffness with matrix elasticity but later continuously change it with time. We observed upregulation of osteogenic markers on cross-linked films and increased lamin A/C expression. We show that manipulating Lamin-A/C expression in stem cells also directs cell lineage with knockdown favoring adipogenesis and over expression favoring osteogenesis. We found positive correlation between matrix and nucleus mechanics and that they have a synergistic effect on hMSCs differentiation potential.

Ivanovska, Irena; Discher, Dennis

2012-02-01

82

Dinosaur Paleobiology Geology 331  

E-print Network

Dinosaur Paleobiology Geology 331 Paleontology #12;Dinosaurs are popular with the public #12;Jack Horner, Montana State Univ. #12;Field Work in Montana #12;A dinosaur "drumstick" in its field jacket. #12;Abundant vascular canals in dinosaur bone support the warm- blooded theory #12;Thin section of dinosaur

Kammer, Thomas

83

Changes in glycosaminoglycan structure on differentiation of human embryonic stem cells towards mesoderm and endoderm lineages  

E-print Network

Changes in glycosaminoglycan structure on differentiation of human embryonic stem cells towards proteoglycans with stem cell differentiation. Methods: Human embryonic stem cell line WA09 (H9. Conclusions: Differentiation of embryonic stem cells markedly changes the proteoglycanome. General

Linhardt, Robert J.

84

Life Cycle and Morphology of a Cambrian Stem-Lineage Loriciferan  

PubMed Central

Cycloneuralians form a rich and diverse element within Cambrian assemblages of exceptionally preserved fossils. Most resemble priapulid worms whereas other Cycloneuralia (Nematoda, Nematomorpha, Kinorhyncha, Loricifera), well known at the present day, have little or no fossil record. First reports of Sirilorica Peel, 2010 from the lower Cambrian Sirius Passet fauna of North Greenland described a tubular lorica covering the abdomen and part of a well developed introvert with a circlet of 6 grasping denticles near the lorica. The introvert is now known to terminate in a narrow mouth tube, while a conical anal field is also developed. Broad muscular bands between the plates in the lorica indicate that it was capable of movement by rhythmic expansion and contraction of the lorica. Sirilorica is regarded as a macrobenthic member of the stem-lineage of the miniaturised, interstitial, present day Loricifera. Like loriciferans, Sirilorica is now known to have grown by moulting. Evidence of the life cycle of Sirilorica is described, including a large post-larval stage and probably an initial larva similar to that of the middle Cambrian fossil Orstenoloricusshergoldii. PMID:23991198

Peel, John S.; Stein, Martin; Kristensen, Reinhardt Møbjerg

2013-01-01

85

Ddx46 Is Required for Multi-Lineage Differentiation of Hematopoietic Stem Cells in Zebrafish  

PubMed Central

Balanced and precisely controlled processes between self-renewal and differentiation of hematopoietic stem cells (HSCs) into all blood lineages are critical for vertebrate definitive hematopoiesis. However, the molecular mechanisms underlying the maintenance and differentiation of HSCs have not been fully elucidated. Here, we show that zebrafish Ddx46, encoding a DEAD-box RNA helicase, is expressed in HSCs of the caudal hematopoietic tissue (CHT). The number of HSCs expressing the molecular markers cmyb or T-cell acute lymphocytic leukemia 1 (tal1) was markedly reduced in Ddx46 mutants. However, massive cell death of HSCs was not detected, and proliferation of HSCs was normal in the CHT of the mutants at 48?h postfertilization. We found that myelopoiesis occurred, but erythropoiesis and lymphopoiesis were suppressed, in Ddx46 mutants. Consistent with these results, the expression of spi1, encoding a regulator of myeloid development, was maintained, but the expression of gata1a, encoding a regulator of erythrocyte development, was downregulated in the mutants. Taken together, our results provide the first genetic evidence that zebrafish Ddx46 is required for the multilineage differentiation of HSCs during development, through the regulation of specific gene expressions. PMID:23635340

Hirabayashi, Ryo; Hozumi, Shunya; Higashijima, Shin-ichi

2013-01-01

86

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

87

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

88

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

89

Dinosaur Dioramas.  

ERIC Educational Resources Information Center

Describes an art project for second-grade students where in over five class periods, they create fired clay dinosaur sculptures with dioramas as the background. States that this project, the culminating activity for a sculpture unit, teaches students many art terms and uses of different media. (CMK)

Scheinkman, Nancy

2001-01-01

90

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.

91

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.

92

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.

93

Asymmetric Division and Lineage Commitment at the Level of Hematopoietic Stem Cells: Inference from Differentiation in Daughter Cell and Granddaughter Cell Pairs  

Microsoft Academic Search

How hematopoietic stem cells (HSCs) commit to a particular lineage is unclear. A high degree of HSC purification enabled us to address this issue at the clonal level. Single-cell transplantation studies revealed that 40% of the CD34 ? \\/low , c-Kit ? , Sca-1 ? , and lineage marker ? (CD34 ? KSL) cells in adult mouse bone marrow were

Hina Takano; Hideo Ema; Kazuhiro Sudo; Hiromitsu Nakauchi

2004-01-01

94

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

95

Adult Thymus Contains FoxN1? Epithelial Stem Cells that Are Bipotent for Medullary and Cortical Thymic Epithelial Lineages  

PubMed Central

Summary 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

2014-01-01

96

Paracrine Factors of Mesenchymal Stem Cells Recruit Macrophages and Endothelial Lineage Cells and Enhance Wound Healing  

PubMed Central

Bone marrow derived mesenchymal stem cells (BM-MSCs) have been shown to enhance wound healing; however, the mechanisms involved are barely understood. In this study, we examined paracrine factors released by BM-MSCs and their effects on the cells participating in wound healing compared to those released by dermal fibroblasts. Analyses of BM-MSCs with Real-Time PCR and of BM-MSC-conditioned medium by antibody-based protein array and ELISA indicated that BM-MSCs secreted distinctively different cytokines and chemokines, such as greater amounts of VEGF-?, IGF-1, EGF, keratinocyte growth factor, angiopoietin-1, stromal derived factor-1, macrophage inflammatory protein-1alpha and beta and erythropoietin, compared to dermal fibroblasts. These molecules are known to be important in normal wound healing. BM-MSC-conditioned medium significantly enhanced migration of macrophages, keratinocytes and endothelial cells and proliferation of keratinocytes and endothelial cells compared to fibroblast-conditioned medium. Moreover, in a mouse model of excisional wound healing, where concentrated BM-MSC-conditioned medium was applied, accelerated wound healing occurred compared to administration of pre-conditioned or fibroblast-conditioned medium. Analysis of cell suspensions derived from the wound by FACS showed that wounds treated with BM-MSC-conditioned medium had increased proportions of CD4/80-postive macrophages and Flk-1-, CD34- or c-kit-positive endothelial (progenitor) cells compared to wounds treated with pre-conditioned medium or fibroblast-conditioned medium. Consistent with the above findings, immunohistochemical analysis of wound sections showed that wounds treated with BM-MSC-conditioned medium had increased abundance of macrophages. Our results suggest that factors released by BM-MSCs recruit macrophages and endothelial lineage cells into the wound thus enhancing wound healing. PMID:18382669

Chen, Liwen; Tredget, Edward E.; Wu, Philip Y. G.; Wu, Yaojiong

2008-01-01

97

Metabolic Biomarkers of Prenatal Alcohol Exposure in Human Embryonic Stem Cell-derived Neural Lineages  

PubMed Central

Background Fetal alcohol spectrum disorders (FASD) are a leading cause of neurodevelopmental disability. The mechanisms underlying FASD are incompletely understood, and biomarkers to identify those at risk are lacking. Here, we perform metabolomic analysis of embryoid bodies and neural lineages derived from human embryonic stem (hES) cell to identify the neural secretome produced in response to ethanol exposure. Methods WA01 and WA09 hES cells were differentiated into embryoid bodies, neural progenitors or neurons. Cells along this progression were cultured for four days with 0%, 0.1% or 0.3% ethanol. Supernatants were subjected to C18 chromatography followed by ESI-QTOF-MS. Features were annotated using public databases and the identities of four putative biomarkers were confirmed with purified standards and comparative MS/MS. Results Ethanol treatment induced statistically significant changes to metabolite abundance in human embryoid bodies (180 features), neural progenitors (76 features) and neurons (42 features). There were no shared significant features between different cell types. Fifteen features showed a dose-response to ethanol. Four chemical identities were confirmed; L-thyroxine, 5’-methylthioadenosine, and the tryptophan metabolites L-kynurenine, and indoleacetaldehyde. One feature with a putative annotation of succinyladenosine was significantly increased in both ethanol treatments. Additional features were selective to ethanol treatment but were not annotated in public databases. Conclusions Ethanol exposure induces statistically significant changes to the metabolome profile of human embryoid bodies, neural progenitors and neurons. Several of these metabolites are normally present in human serum, suggesting their usefulness as potential serum FASD biomarkers. These findings suggest the biochemical pathways that are affected by ethanol in the developing nervous system and delineate mechanisms of alcohol injury during human development. PMID:22324771

Palmer, Jessica A.; Poenitzsch, Ashley M.; Smith, Susan M.; Conard, Kevin R.; West, Paul R.; Cezar, Gabriela G.

2012-01-01

98

Convergence of stem cell behaviors and genetic regulation between animals and plants: insights from the Arabidopsis thaliana stomatal lineage  

PubMed Central

Plants and animals are two successful, but vastly different, forms of complex multicellular life. In the 1600 million years since they shared a common unicellular ancestor, representatives of these kingdoms have had ample time to devise unique strategies for building and maintaining themselves, yet they have both developed self-renewing stem cell populations. Using the cellular behaviors and the genetic control of stomatal lineage of Arabidopsis as a focal point, we find current data suggests convergence of stem cell regulation at developmental and molecular levels. Comparative studies between evolutionary distant groups, therefore, have the power to reveal the logic behind stem cell behaviors and benefit both human regenerative medicine and plant biomass production. PMID:25184043

Matos, Juliana L.

2014-01-01

99

Dinosaur Breath  

NSDL National Science Digital Library

Through discussion and hands-on experimentation, learners examine 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. Learners 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.

Boulder, University O.

2007-01-01

100

Thymopentin enhances the generation of T-cell lineage derived from human embryonic stem cells in vitro.  

PubMed

Thymopentin is a group of biologically active peptide secreted mainly by the epithelial cells of thymic cortex and medulla. Whether it promotes T cells production from human embryonic stem cells(hESCs) in vitro remains an elusive issue. In the present study, we develop a novel strategy that enhances T-cell lineage differentiation of hESCs in collagen matrix culture by sequential cytokine cocktails treatment combined with thymopentin stimulation. We observed that approximately 30.75% cells expressed CD34 on day 14 of the cultures and expressed the surface markers of erythroid, lymphoid and myeloid lineages. The results of colony assays and gene expressions by RT-PCR analysis also demonstrated that hematopoietic progenitor cells (HPCs) derived from hESCs were capable of multi-lineage differentiation. Further study revealed that culturing with thymopentin treatment, the CD34(+)CD45RA(+)CD7(+) cells sorted from HPCs expressed T-cell-related genes, IKAROS, DNTT, TCR? and TCR?, and T-cell surface markers, CD3, cytoplasmic CD3, CD5, CD27, TCR??, CD4 and CD8. The differentiated cells produced the cytokines including IFN-?, IL-2 and TNF-? in response to stimulation, providing the evidence for T-cell function of these cells. In conclusion, thymopentin enhances T-cell lineage differentiation from hESCs in vitro by mimicking thymus peptide environment in vivo. PMID:25576384

Zhu, Ming-Xia; Wan, Wen-Li; Li, Hai-Shen; Wang, Jing; Chen, Gui-An; Ke, Xiao-Yan

2015-02-15

101

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.

102

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

103

Dinosaur biomechanics.  

PubMed

Biomechanics has made large contributions to dinosaur biology. It has enabled us to estimate both the speeds at which dinosaurs generally moved and the maximum speeds of which they may have been capable. It has told us about the range of postures they could have adopted, for locomotion and for feeding, and about the problems of blood circulation in sauropods with very long necks. It has made it possible to calculate the bite forces of predators such as Tyrannosaurus, and the stresses they imposed on its skull; and to work out the remarkable chewing mechanism of hadrosaurs. It has shown us how some dinosaurs may have produced sounds. It has enabled us to estimate the effectiveness of weapons such as the tail spines of Stegosaurus. In recent years, techniques such as computational tomography and finite element analysis, and advances in computer modelling, have brought new opportunities. Biomechanists should, however, be especially cautious in their work on animals known only as fossils. The lack of living specimens and even soft tissues oblige us to make many assumptions. It is important to be aware of the often wide ranges of uncertainty that result. PMID:16822743

Alexander, R McNeill

2006-08-01

104

TECHNICAL RESPONSE DINOSAUR EVOLUTION  

E-print Network

TECHNICAL RESPONSE DINOSAUR EVOLUTION Response to Comment on "A Jurassic ornithischian dinosaur ornithischian dinosaur Kulindadromeus as feather-like appendages and alternatively proposes that the compound of >150-million-year-old fossils (1), he fails to explain the marked regionalization across the dinosaur

Benton, Michael

105

Dinosaur Books for Kids  

NSDL National Science Digital Library

This dinosaur reference list has 25 kid-friendly books on a range of related topics. The author, publisher, and publication date are given for each title. The list includes illustrated compilations of the wide variety of dinosaurs that once roamed the Earth, accounts of what it's like to go digging for dinosaurs and theories about what killed off the dinosaurs.

106

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.

107

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

108

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.

2014-04-14

109

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.

110

Muscle-derived stem cells isolated as non-adherent population give rise to cardiac, skeletal muscle and neural lineages  

SciTech Connect

Stem cells with the ability to differentiate in specialized cell types can be extracted from a wide array of adult tissues including skeletal muscle. Here we have analyzed a population of cells isolated from skeletal muscle on the basis of their poor adherence on uncoated or collagen-coated dishes that show multi-lineage differentiation in vitro. When analysed under proliferative conditions, these cells express stem cell surface markers Sca-1 (65%) and Bcrp-1 (80%) but also MyoD (15%), Neuronal {beta} III-tubulin (25%), GFAP (30%) or Nkx2.5 (1%). Although capable of growing as non-attached spheres for months, when given an appropriate matrix, these cells adhere giving rise to skeletal muscle, neuronal and cardiac muscle cell lineages. A similar cell population could not be isolated from either bone marrow or cardiac tissue suggesting their specificity to skeletal muscle. When injected into damaged muscle, these non-adherent muscle-derived cells are retrieved expressing Pax7, in a sublaminar position characterizing satellite cells and participate in forming new myofibers. These data show that a non-adherent stem cell population can be specifically isolated and expanded from skeletal muscle and upon attachment to a matrix spontaneously differentiate into muscle, cardiac and neuronal lineages in vitro. Although competing with resident satellite cells, these cells are shown to significantly contribute to repair of injured muscle in vivo supporting that a similar muscle-derived non-adherent cell population from human muscle may be useful in treatment of neuromuscular disorders.

Arsic, Nikola; Mamaeva, Daria; Lamb, Ned J. [Cell Biology Unit, Institute for Human Genetics, CNRS, 141 rue de la Cardonille, Montpellier (France); Fernandez, Anne [Cell Biology Unit, Institute for Human Genetics, CNRS, 141 rue de la Cardonille, Montpellier (France)], E-mail: af@acrux.igh.cnrs.fr

2008-04-01

111

Expression Patterns of Cancer-Testis Antigens in Human Embryonic Stem Cells and Their Cell Derivatives Indicate Lineage Tracks  

PubMed Central

Pluripotent stem cells can differentiate into various lineages but undergo genetic and epigenetic changes during long-term cultivation and, therefore, require regular monitoring. The expression patterns of cancer-testis antigens (CTAs) MAGE-A2, -A3, -A4, -A6, -A8, -B2, and GAGE were examined in undifferentiated human embryonic stem (hES) cells, their differentiated derivatives, teratocarcinoma (hEC) cells, and cancer cell lines of neuroectodermal and mesodermal origin. Undifferentiated hES cells and embryoid body cells expressed MAGE-A3, -A6, -A4, -A8, and GAGEs while later differentiated derivatives expressed only MAGE-A8 or MAGE-A4. Likewise, mouse pluripotent stem cells also express CTAs of Magea but not Mageb family. Despite similarity of the hES and hEC cell expression patterns, MAGE-A2 and MAGE-B2 were detected only in hEC cells but not in hES cells. Moreover, our analysis has shown that CTAs are aberrantly expressed in cancer cell lines and display low tissue specificity. The identification of CTA expression patterns in pluripotent stem cells and their derivatives may be useful for isolation of abnormally CTA-expressing cells to improve the safety of stem-cell based therapy. PMID:21785609

Lifantseva, Nadya; Koltsova, Anna; Krylova, Tatyana; Yakovleva, Tatyana; Poljanskaya, Galina; Gordeeva, Olga

2011-01-01

112

Transcriptomic and phenotypic analysis of murine embryonic stem cell derived BMP2 + lineage cells: an insight into mesodermal patterning  

Microsoft Academic Search

Background  Bone morphogenetic protein (BMP)2 is a late mesodermal marker expressed during vertebrate development and plays a crucial\\u000a role in early embryonic development. The nature of the BMP2-expressing cells during the early stages of embryonic development,\\u000a their transcriptome and cell phenotypes developed from these cells have not yet been characterized.\\u000a \\u000a \\u000a \\u000a \\u000a Results  We generated a transgenic BMP2 embryonic stem (ES) cell lineage expressing

Michael Xavier Doss; Shuhua Chen; Johannes Winkler; Rita Hippler-Altenburg; Margareta Odenthal; Claudia Wickenhauser; Sridevi Balaraman; Herbert Schulz; Oliver Hummel; Norbert Hübner; Nandini Ghosh-Choudhury; Isaia Sotiriadou; Jürgen Hescheler; Agapios Sachinidis

2007-01-01

113

Lineage switching in acute leukemias: a consequence of stem cell plasticity?  

PubMed

Acute leukemias are the most common cancer in childhood and characterized by the uncontrolled production of hematopoietic precursor cells of the lymphoid or myeloid series within the bone marrow. Even when a relatively high efficiency of therapeutic agents has increased the overall survival rates in the last years, factors such as cell lineage switching and the rise of mixed lineages at relapses often change the prognosis of the illness. During lineage switching, conversions from lymphoblastic leukemia to myeloid leukemia, or vice versa, are recorded. The central mechanisms involved in these phenomena remain undefined, but recent studies suggest that lineage commitment of plastic hematopoietic progenitors may be multidirectional and reversible upon specific signals provided by both intrinsic and environmental cues. In this paper, we focus on the current knowledge about cell heterogeneity and the lineage switch resulting from leukemic cells plasticity. A number of hypothetical mechanisms that may inspire changes in cell fate decisions are highlighted. Understanding the plasticity of leukemia initiating cells might be fundamental to unravel the pathogenesis of lineage switch in acute leukemias and will illuminate the importance of a flexible hematopoietic development. PMID:22852088

Dorantes-Acosta, Elisa; Pelayo, Rosana

2012-01-01

114

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.

115

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

116

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

117

The effect of bioartificial constructs that mimic myocardial structure and biomechanical properties on stem cell commitment towards cardiac lineage.  

PubMed

Despite the enormous progress in the treatment of coronary artery diseases, they remain the most common cause of heart failure in the Western countries. New translational therapeutic approaches explore cardiomyogenic differentiation of various types of stem cells in combination with tissue-engineered scaffolds. In this study we fabricated PHBHV/gelatin constructs mimicking myocardial structural properties. Chemical structure and molecular interaction between material components induced specific properties to the substrate in terms of hydrophilicity degree, porosity and mechanical characteristics. Viability and proliferation assays demonstrated that these constructs allow adhesion and growth of mesenchymal stem cells (MSCs) and cardiac resident non myocytic cells (NMCs). Immunofluorescence analysis demonstrated that stem cells cultured on these constructs adopt a distribution mimicking the three-dimensional cell alignment of myocardium. qPCR and immunofluorescence analyses showed the ability of this construct to direct initial MSC and NMC lineage specification towards cardiomyogenesis: both MSCs and NMCs showed the expression of the cardiac transcription factor GATA-4, fundamental for early cardiac commitment. Moreover NMCs also acquired the expression of the cardiac transcription factors Nkx2.5 and TBX5 and produced sarcomeric proteins. This work may represent a new approach to induce both resident and non-resident stem cells to cardiac commitment in a 3-D structure, without using additional stimuli. PMID:24099712

Cristallini, Caterina; Cibrario Rocchietti, Elisa; Accomasso, Lisa; Folino, Anna; Gallina, Clara; Muratori, Luisa; Pagliaro, Pasquale; Rastaldo, Raffaella; Raimondo, Stefania; Saviozzi, Silvia; Sprio, Andrea E; Gagliardi, Mariacristina; Barbani, Niccoletta; Giachino, Claudia

2014-01-01

118

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

119

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.

120

mTORC2 regulates mechanically induced cytoskeletal reorganization and lineage selection in marrow derived mesenchymal stem cells  

PubMed Central

The cell cytoskeleton interprets and responds to physical cues from the microenvironment. Applying mechanical force to mesenchymal stem cells induces formation of a stiffer cytoskeleton, which biases against adipogenic differentiation and toward osteoblastogenesis. mTORC2, the mTOR complex defined by its binding partner rictor, is implicated in resting cytoskeletal architecture and is activated by mechanical force. We asked if mTORC2 played a role in mechanical adaptation of the cytoskeleton. We found that during bi-axial strain induced cytoskeletal restructuring, mTORC2 and Akt co-localize with newly assembled focal adhesions (FA). Disrupting the function of mTORC2, or that of its downstream substrate Akt, prevented mechanically-induced F-actin stress fiber development. mTORC2 becomes associated with vinculin during strain, and knock-down of vinculin prevents mTORC2 activation. In contrast, mTORC2 is not recruited to the FA complex during its activation by insulin, nor does insulin alter cytoskeletal structure. Further, when rictor was knocked down, the ability of MSC to enter the osteoblastic lineage was reduced, and when cultured in adipogenic medium, rictor-deficient MSC showed accelerated adipogenesis. This indicated that cytoskeletal remodeling promotes osteogenesis over adipogenesis. In sum, our data show that mTORC2 is involved in stem cell responses to biophysical stimuli, regulating both signaling and cytoskeletal reorganization. As such, mechanical activation of mTORC2 signaling participates in mesenchymal stem cell lineage selection, preventing adipogenesis by preserving ?-catenin and stimulating osteogenesis by generating a stiffer cytoskeleton. PMID:23821483

Sen, Buer; Xie, Zhihui; Case, Natasha; Thompson, William R.; Uzer, Gunes; Styner, Maya; Rubin, Janet

2013-01-01

121

Brushing up on Dinosaurs.  

ERIC Educational Resources Information Center

Describes new methods of reconstruction of dinosaurs using skeletons, mummified skin, and muscle scars, along with clay and paint. Examines some inaccuracies in dinosaur's physical characteristics and behaviors suggested by recent findings. (TW)

Weisburd, Stefi

1986-01-01

122

Dinosaur Sock Puppet  

NSDL National Science Digital Library

In this activity about dinosaurs, learners first participate in a group discussion about where and when dinosaurs lived, how big they were, and who studies them and how. Then, learners use their imaginations to create dinosaur puppets with recycled art supplies and a sock, while considering what features their dinosaurs need. Learners make up stories to go along with their puppets and are encouraged to put on impromptu shows. A list of discussion questions is included in this resource to further the learning.

Omsi

2004-01-01

123

Specific MicroRNAs Are Preferentially Expressed by Skin Stem Cells To Balance Self-Renewal and Early Lineage Commitment  

PubMed Central

Summary Increasing evidence suggests that microRNAs may play important roles in regulating self-renewal and differentiation in mammalian stem cells (SCs). Here, we explore this issue in skin. We first characterize microRNA expression profiles of skin SCs versus their committed proliferative progenies and identify a microRNA subset associating with “stemness”. Of these, miR-125b is dramatically downregulated in early SC-progeny. We engineer an inducible mice system and show that when miR-125b is sustained in SC-progenies, tissue balance is reversibly skewed towards stemness at the expense of epidermal, oil-gland and HF differentiation. Using gain-and-loss of function in vitro, we further implicate miR-125b as a repressor of SC differentiation. In vivo, transcripts repressed upon miR-125b induction are enriched >700% for predicted miR-125b targets normally downregulated upon SC-lineage commitment. We verify some of these miR-125b targets, and show that Blimp1 and VDR in particular can account for many tissue imbalances we see when miR-125b is deregulated. PMID:21362569

Zhang, Liang; Stokes, Nicole; Polak, Lisa; Fuchs, Elaine

2011-01-01

124

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

125

Palaeontology Dinosaur extinction  

E-print Network

Palaeontology Dinosaur extinction: closing the `3 m gap' Tyler R. Lyson1,2,*, Antoine Bercovici3- avian dinosaurs was ignited by the publication of the Cretaceous­Tertiary (K­T) asteroid impact theory and has seen 30 years of dispute over the position of the stratigraphically youngest in situ dinosaur

Sargis, Eric J.

126

Dinosaur Extinction: Changing Views  

E-print Network

99 Dinosaur Extinction: Changing Views J. David Archibald Department of Biology San Diego State Asia. His 1996 book Dinosaur Extinction and the End of an Era: What the Fossils Say (Columbia University Press) documents what we know of the fossil record at the time of dinosaur extinction

Archibald, J. David

127

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

128

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

129

ERK2 suppresses self-renewal capacity of embryonic stem cells, but is not required for multi-lineage commitment.  

PubMed

Activation of the FGF-ERK pathway is necessary for naïve mouse embryonic stem (ES) cells to exit self-renewal and commit to early differentiated lineages. Here we show that genetic ablation of Erk2, the predominant ERK isozyme expressed in ES cells, results in hyper-phosphorylation of ERK1, but an overall decrease in total ERK activity as judged by substrate phosphorylation and immediate-early gene (IEG) induction. Normal induction of this subset of canonical ERK targets, as well as p90RSK phosphorylation, was rescued by transgenic expression of either ERK1 or ERK2 indicating a degree of functional redundancy. In contrast to previously published work, Erk2-null ES cells exhibited no detectable defect in lineage specification to any of the three germ layers when induced to differentiate in either embryoid bodies or in defined neural induction conditions. However, under self-renewing conditions Erk2-null ES cells express increased levels of the pluripotency-associated transcripts, Nanog and Tbx3, a decrease in Nanog-GFP heterogeneity, and exhibit enhanced self-renewal in colony forming assays. Transgenic add-back of ERK2 is capable of restoring normal pluripotent gene expression and self-renewal capacity. We show that ERK2 contributes to the destabilization of ES cell self-renewal by reducing expression of pluripotency genes, such as Nanog, but is not specifically required for the early stages of germ layer specification. PMID:23613754

Hamilton, William B; Kaji, Keisuke; Kunath, Tilo

2013-01-01

130

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

131

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

132

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

133

Transcription factor-induced lineage programming of noradrenaline and motor neurons from embryonic stem cells.  

PubMed

An important goal in stem cell biology is to develop methods for efficient generation of clinically interesting cell types from relevant stem cell populations. This is particularly challenging for different types of neurons of the central nervous system where hundreds of distinct neuronal cell types are generated during embryonic development. We previously used a strategy based on forced transcription factor expression in embryonic stem cell-derived neural progenitors to generate specific types of neurons, including dopamine and serotonin neurons. Here, we extend these studies and show that noradrenergic neurons can also be generated from pluripotent embryonic stem cells by forced expression of the homeobox transcription factor Phox2b under the signaling influence of fibroblast growth factor 8 (FGF8) and bone morphogenetic proteins. In neural progenitors exposed to FGF8 and sonic hedgehog both Phox2b and the related Phox2a instead promoted the generation of neurons with the characteristics of mid- and hindbrain motor neurons. The efficient generation of these neuron types enabled a comprehensive genome-wide gene expression analysis that provided further validation of the identity of generated cells. Moreover, we also demonstrate that the generated cell types are amenable to drug testing in vitro and we show that variants of the differentiation protocols can be applied to cultures of human pluripotent stem cells for the generation of human noradrenergic and visceral motor neurons. Thus, these studies provide a basis for characterization of yet an additional highly clinically relevant neuronal cell type. PMID:24549637

Mong, Jamie; Panman, Lia; Alekseenko, Zhanna; Kee, Nigel; Stanton, Lawrence W; Ericson, Johan; Perlmann, Thomas

2014-03-01

134

Knocking off their Sox: lineage-specific repression by Polycomb in epidermal stem cells  

PubMed Central

EMBO J 32 14, 1990–2000 doi:10.1038/emboj.2013.110; published online 05142013 A recent publication in The EMBO Journal (Bardot et al, 2013) provides novel insights into lineage specification during the development of the mouse skin. Ezhkova and colleagues demonstrate that Ezh1 and Ezh2, core enzymes of the Polycomb Repressive Complex (PRC), restrict differentiation of Merkel cells, a specialized population of mechanosensory cells by directly repressing the cell fate determinant transcription factor (TF) Sox2 in epidermal progenitors. PMID:23727885

Tumbar, Tudorita

2013-01-01

135

Research potential of multi-lineage chicken amniotic mesenchymal stem cells.  

PubMed

Amniotic mesenchymal stem cells (AMSCs) express octamer binding transcription factor 4 (Oct-4), which is necessary for maintaining the undifferentiated state of pluripotent stem cells. AMSCs also express CD29, CD44 and vimentin, which are specific markers of mesenchymal cells. We studied the biological characteristics and potential for cell therapy of AMSCs derived from 8-day-old chicken embryos. We induced the AMSCs to differentiate into adipocytes, osteoblasts and myocardial cells and used immunofluorescence, reverse transcription-polymerase chain reaction (RT-PCR) assays to detect the expressions of specific markers of AMSCs and differentiated cells. To assess the differentiation capacity of AMSCs, passage four cells were induced to differentiate into adipocytes, osteoblasts and myocardial cells. These results suggested that AMSCs isolated from chicken embryos exhibited the characteristics of multipotent stem cells. AMSCs, therefore, may be potential candidates for cellular transplantation therapy and tissue engineering. PMID:24047150

Li, X; Gao, Y; Hua, J; Bian, Y; Mu, R; Guan, W; Ma, Y

2014-04-01

136

The osteogenic or adipogenic lineage commitment of human mesenchymal stem cells is determined by protein kinase C delta.  

PubMed

BackgroundMesenchymal stem cells (MSCs) have the potential to differentiate into specialized cell lineages such as osteoblasts and adipocytes in vitro. There exists a reciprocal relationship between osteogenic and adipogenic differentiation of MSCs that an osteogenic phenotype occurs at the expense of an adipogenic phenotype and vice versa, which in turn influence one another¿s phenotype through negative feedback loops. Thus, it is important to understand what signaling molecules modulate the lineage commitment of MSCs. Protein kinase C (PKC) plays a central role in cellular signal transduction for mediating diverse biological functions, and dysregulation of PKC activity is involved in various metabolic diseases including cancer, diabetes, and heart disease. Although the role of individual PKC isoforms has been investigated in various fields, the potential role of PKC in bone metabolism is not completely understood. In this study, we investigated the potential role of PKC¿ in osteogenic lineage commitment of human bone marrow-derived mesenchymal stem cells (hBMSCs).ResultsWe observed that expression and phosphorylation of PKC¿ were increased during osteogenic differentiation of hBMSCs. Pharmacological inhibition and genetic ablation of PKC¿ in hBMSCs resulted in a significant attenuation of osteogenic differentiation as evidenced by reduced ALP activity and ECM mineralization, as well as down-regulation of the expression of osteoblast-specific genes. These effects were also accompanied by induction of adipogenic differentiation and up-regulation of the expression of adipocyte-specific genes involved in lipid synthesis in osteogenic induction of hBMSCs. Additionally, the activation of AMPK, which is a key cellular energy sensor, induced osteogenesis of hBMSCs. However, the inhibition of AMPK activity by compound C did not affect the activation of PKC¿ at all, indicating that there is no direct correlation between AMPK and PKC¿ in osteogenesis of hBMSCs.ConclusionsThese results suggest that PKC¿ is a critical regulator for the balance between osteogenesis and adipogenesis of hBMSCs and thus has a potential novel therapeutic target for the treatment of metabolic bone diseases. PMID:25420887

Lee, Sooho; Cho, Hee-Yeon; Bui, Hang; Kang, Dongchul

2014-11-25

137

Prohibitin 2 Regulates the Proliferation and Lineage-Specific Differentiation of Mouse Embryonic Stem Cells in Mitochondria  

PubMed Central

Background The pluripotent state of embryonic stem (ES) cells is controlled by a network of specific transcription factors. Recent studies also suggested the significant contribution of mitochondria on the regulation of pluripotent stem cells. However, the molecules involved in these regulations are still unknown. Methodology/Principal Findings In this study, we found that prohibitin 2 (PHB2), a pleiotrophic factor mainly localized in mitochondria, is a crucial regulatory factor for the homeostasis and differentiation of ES cells. PHB2 was highly expressed in undifferentiated mouse ES cells, and the expression was decreased during the differentiation of ES cells. Knockdown of PHB2 induced significant apoptosis in pluripotent ES cells, whereas enhanced expression of PHB2 contributed to the proliferation of ES cells. However, enhanced expression of PHB2 strongly inhibited ES cell differentiation into neuronal and endodermal cells. Interestingly, only PHB2 with intact mitochondrial targeting signal showed these specific effects on ES cells. Moreover, overexpression of PHB2 enhanced the processing of a dynamin-like GTPase (OPA1) that regulates mitochondrial fusion and cristae remodeling, which could induce partial dysfunction of mitochondria. Conclusions/Significance Our results suggest that PHB2 is a crucial mitochondrial regulator for homeostasis and lineage-specific differentiation of ES cells. PMID:24709813

Komazaki, Shinji; Enomoto, Kei; Seki, Yasuhiro; Wang, Ying Ying; Ishigaki, Yohei; Ninomiya, Naoto; Noguchi, Taka-aki K.; Kokubu, Yuko; Ohnishi, Keigoh; Nakajima, Yoshiro; Kato, Kaoru; Intoh, Atsushi; Takada, Hitomi; Yamakawa, Norio; Wang, Pi-Chao; Asashima, Makoto; Kurisaki, Akira

2014-01-01

138

CD271/p75(NTR) inhibits the differentiation of mesenchymal stem cells into osteogenic, adipogenic, chondrogenic, and myogenic lineages.  

PubMed

We describe a novel role for CD271 in the differentiation of mesenchymal stem cells (MSCs), including deciduous dental pulp stem cells (DDPSCs) and murine multipotent MSCs (C3H10T1/2 cells). The CD271(+) subpopulation of deciduous dental pulp cells (CD271(+)/DDPSCs) and the forced expression of CD271 in C3H10T1/2 (10T271) were analyzed by fluorescence-activated cell sorting. CD271 expression was detected in DDPSCs that expressed both CD44 and CD90, simultaneously, and the clonogenic capacity of the CD271(+)/DDPSCs was higher than that of the CD271(-)/DDPSCs that expressed both CD44 and CD90. Further, the differentiation of CD271(+)/DDPSCs into osteoblasts and adipocytes was inhibited although CD271(-)/DDPSCs were capable of differentiating into osteoblasts and adipocytes. CD271 was overexpressed in C3H10T1/2 cells, which have the potential to differentiate into osteoblasts, adipocytes, chondrocytes, and myocytes. CD271 inhibited the differentiation of C3H10T1/2 cells into any of these lineages. These results indicate a role for CD271 in inhibiting the differentiation of MSCs. PMID:21142793

Mikami, Yoshikazu; Ishii, Yumiko; Watanabe, Nobukazu; Shirakawa, Tetsuo; Suzuki, Shinnosuke; Irie, Seiko; Isokawa, Keitaro; Honda, Masaki J

2011-05-01

139

Dual small-molecule targeting of SMAD signaling stimulates human induced pluripotent stem cells toward neural lineages.  

PubMed

Incurable neurological disorders such as Parkinson's disease (PD), Huntington's disease (HD), and Alzheimer's disease (AD) are very common and can be life-threatening because of their progressive disease symptoms with limited treatment options. To provide an alternative renewable cell source for cell-based transplantation and as study models for neurological diseases, we generated induced pluripotent stem cells (iPSCs) from human dermal fibroblasts (HDFs) and then differentiated them into neural progenitor cells (NPCs) and mature neurons by dual SMAD signaling inhibitors. Reprogramming efficiency was improved by supplementing the histone deacethylase inhibitor, valproic acid (VPA), and inhibitor of p160-Rho associated coiled-coil kinase (ROCK), Y-27632, after retroviral transduction. We obtained a number of iPS colonies that shared similar characteristics with human embryonic stem cells in terms of their morphology, cell surface antigens, pluripotency-associated gene and protein expressions as well as their in vitro and in vivo differentiation potentials. After treatment with Noggin and SB431542, inhibitors of the SMAD signaling pathway, HDF-iPSCs demonstrated rapid and efficient differentiation into neural lineages. Six days after neural induction, neuroepithelial cells (NEPCs) were observed in the adherent monolayer culture, which had the ability to differentiate further into NPCs and neurons, as characterized by their morphology and the expression of neuron-specific transcripts and proteins. We propose that our study may be applied to generate neurological disease patient-specific iPSCs allowing better understanding of disease pathogenesis and drug sensitivity assays. PMID:25207966

Wattanapanitch, Methichit; Klincumhom, Nuttha; Potirat, Porntip; Amornpisutt, Rattaya; Lorthongpanich, Chanchao; U-pratya, Yaowalak; Laowtammathron, Chuti; Kheolamai, Pakpoom; Poungvarin, Niphon; Issaragrisil, Surapol

2014-01-01

140

Intracellular Inactivation of Thyroid Hormone Is a Survival Mechanism for Muscle Stem Cell Proliferation and Lineage Progression  

PubMed Central

Summary Precise control of the thyroid hormone (T3)-dependent transcriptional program is required by multiple cell systems, including muscle stem cells. Deciphering how this is achieved and how the T3 signal is controlled in stem cell niches is essentially unknown. We report that in response to proliferative stimuli such as acute skeletal muscle injury, type 3 deiodinase (D3), the thyroid hormone-inactivating enzyme, is induced in satellite cells where it reduces intracellular thyroid signaling. Satellite cell-specific genetic ablation of dio3 severely impairs skeletal muscle regeneration. This impairment is due to massive satellite cell apoptosis caused by exposure of activated satellite cells to the circulating TH. The execution of this proapoptotic program requires an intact FoxO3/MyoD axis, both genes positively regulated by intracellular TH. Thus, D3 is dynamically exploited in vivo to chronically attenuate TH signaling under basal conditions while also being available to acutely increase gene programs required for satellite cell lineage progression. PMID:25456740

Dentice, Monica; Ambrosio, Raffaele; Damiano, Valentina; Sibilio, Annarita; Luongo, Cristina; Guardiola, Ombretta; Yennek, Siham; Zordan, Paola; Minchiotti, Gabriella; Colao, Annamaria; Marsili, Alessandro; Brunelli, Silvia; Del Vecchio, Luigi; Larsen, P. Reed; Tajbakhsh, Shahragim; Salvatore, Domenico

2014-01-01

141

Intracellular inactivation of thyroid hormone is a survival mechanism for muscle stem cell proliferation and lineage progression.  

PubMed

Precise control of the thyroid hormone (T3)-dependent transcriptional program is required by multiple cell systems, including muscle stem cells. Deciphering how this is achieved and how the T3 signal is controlled in stem cell niches is essentially unknown. We report that in response to proliferative stimuli such as acute skeletal muscle injury, type 3 deiodinase (D3), the thyroid hormone-inactivating enzyme, is induced in satellite cells where it reduces intracellular thyroid signaling. Satellite cell-specific genetic ablation of dio3 severely impairs skeletal muscle regeneration. This impairment is due to massive satellite cell apoptosis caused by exposure of activated satellite cells to the circulating TH. The execution of this proapoptotic program requires an intact FoxO3/MyoD axis, both genes positively regulated by intracellular TH. Thus, D3 is dynamically exploited in vivo to chronically attenuate TH signaling under basal conditions while also being available to acutely increase gene programs required for satellite cell lineage progression. PMID:25456740

Dentice, Monica; Ambrosio, Raffaele; Damiano, Valentina; Sibilio, Annarita; Luongo, Cristina; Guardiola, Ombretta; Yennek, Siham; Zordan, Paola; Minchiotti, Gabriella; Colao, Annamaria; Marsili, Alessandro; Brunelli, Silvia; Del Vecchio, Luigi; Larsen, P Reed; Tajbakhsh, Shahragim; Salvatore, Domenico

2014-12-01

142

Dinosaur eggs discovered inside mother  

NSDL National Science Digital Library

Scientists have discovered a dinosaur that died right before it laid two eggs. Finding dinosaur eggs inside the female, in almost the same position they were in when she died, might answer some tough questions about dinosaur egg-laying.

American Association for the Advancement of Science (AAAS;)

2005-04-14

143

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, Micha?; Richter, Magdalena; Pawlicz, Jaros?aw; Suchorska, Wiktoria M

2014-01-01

144

Generation and Applications of Human Pluripotent Stem Cells Induced into Neural Lineages and Neural Tissues  

PubMed Central

Human pluripotent stem cells (hPSCs) represent a new and exciting field in modern medicine, now the focus of many researchers and media outlets. The hype is well-earned because of the potential of stem cells to contribute to disease modeling, drug screening, and even therapeutic approaches. In this review, we focus first on neural differentiation of these cells. In a second part we compare the various cell types available and their advantages for in vitro modeling. Then we provide a “state-of-the-art” report about two major biomedical applications: (1) the drug and toxicity screening and (2) the neural tissue replacement. Finally, we made an overview about current biomedical research using differentiated hPSCs. PMID:22457650

Martinez, Y.; Dubois-Dauphin, M.; Krause, K.-H.

2012-01-01

145

EphB signaling controls lineage plasticity of adult neural stem cell niche cells  

PubMed Central

Stem cells remain in specialized niches over the lifespan of the organism in many organs to ensure tissue homeostasis and enable regeneration. How the niche is maintained is not understood, but is likely as important as intrinsic stem cell self-renewal capacity for tissue integrity. We here demonstrate a high degree of phenotypic plasticity of the two main niche cell types, ependymal cells and astrocytes, in the neurogenic lateral ventricle walls in the adult mouse brain. In response to a lesion, astrocytes give rise to ependymal cells and ependymal cells give rise to niche astrocytes. We identify EphB2 forward signaling as a key pathway regulating niche cell plasticity. EphB2 acts downstream of Notch and is required for the maintenance of ependymal cell characteristics, thereby inhibiting the transition from ependymal cell to astrocyte. Our results show that niche cell identity is actively maintained and that niche cells retain a high level of plasticity. PMID:21112567

Nomura, Tadashi; Göritz, Christian; Catchpole, Timothy; Henkemeyer, Mark; Frisén, Jonas

2010-01-01

146

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

147

Paracrine Factors of Mesenchymal Stem Cells Recruit Macrophages and Endothelial Lineage Cells and Enhance Wound Healing  

Microsoft Academic Search

Bone marrow derived mesenchymal stem cells (BM-MSCs) have been shown to enhance wound healing; however, the mechanisms involved are barely understood. In this study, we examined paracrine factors released by BM-MSCs and their effects on the cells participating in wound healing compared to those released by dermal fibroblasts. Analyses of BM-MSCs with Real-Time PCR and of BM-MSC-conditioned medium by antibody-based

Liwen Chen; Edward E. Tredget; Philip Y. G. Wu; Yaojiong Wu; Patricia Bozza

2008-01-01

148

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

149

Piwi Is Required in Multiple Cell Types to Control Germline Stem Cell Lineage Development in the Drosophila Ovary  

PubMed Central

The piRNA pathway plays an important role in maintaining genome stability in the germ line by silencing transposable elements (TEs) from fly to mammals. As a highly conserved piRNA pathway component, Piwi is widely expressed in both germ cells and somatic cells in the Drosophila ovary and is required for piRNA production in both cell types. In addition to its known role in somatic cap cells to maintain germline stem cells (GSCs), this study has demonstrated that Piwi has novel functions in somatic cells and germ cells of the Drosophila ovary to promote germ cell differentiation. Piwi knockdown in escort cells causes a reduction in escort cell (EC) number and accumulation of undifferentiated germ cells, some of which show active BMP signaling, indicating that Piwi is required to maintain ECs and promote germ cell differentiation. Simultaneous knockdown of dpp, encoding a BMP, in ECs can partially rescue the germ cell differentiation defect, indicating that Piwi is required in ECs to repress dpp. Consistent with its key role in piRNA production, TE transcripts increase significantly and DNA damage is also elevated in the piwi knockdown somatic cells. Germ cell-specific knockdown of piwi surprisingly causes depletion of germ cells before adulthood, suggesting that Piwi might control primordial germ cell maintenance or GSC establishment. Finally, Piwi inactivation in the germ line of the adult ovary leads to gradual GSC loss and germ cell differentiation defects, indicating the intrinsic role of Piwi in adult GSC maintenance and differentiation. This study has revealed new germline requirement of Piwi in controlling GSC maintenance and lineage differentiation as well as its new somatic function in promoting germ cell differentiation. Therefore, Piwi is required in multiple cell types to control GSC lineage development in the Drosophila ovary. PMID:24658126

Ma, Xing; Wang, Su; Do, Trieu; Song, Xiaoqing; Inaba, Mayu; Nishimoto, Yoshiya; Liu, Lu-ping; Gao, Yuan; Mao, Ying; Li, Hui; McDowell, William; Park, Jungeun; Malanowski, Kate; Peak, Allison; Perera, Anoja; Li, Hua; Gaudenz, Karin; Haug, Jeff; Yamashita, Yukiko; Lin, Haifan; Ni, Jian-quan; Xie, Ting

2014-01-01

150

Electrospun fibre diameter, not alignment, affects mesenchymal stem cell differentiation into the tendon/ligament lineage.  

PubMed

Efforts to develop engineered tendons and ligaments have focused on the use of a biomaterial scaffold and a stem cell source. However, the ideal scaffold microenvironment to promote stem cell differentiation and development of organized extracellular matrix is unknown. Through electrospinning, fibre scaffolds can be designed with tailorable architectures to mimic the intended tissue. In this study, the effects of fibre diameter and orientation were examined by electrospinning thin mats, consisting of small (< 1?µm), medium (1-2?µm) or large (> 2?µm) diameter fibres with either random or aligned fibre orientation. C3H10T1/2 model stem cells were cultured on the six different electrospun mats, as well as smooth spin-coated films, and the morphology, growth and expression of tendon/ligament genes were evaluated. The results demonstrated that fibre diameter affects cellular behaviour more significantly than fibre alignment. Initially, cell density was greater on the small fibre diameter mats, but similar cell densities were found on all mats after an additional week in culture. After 2?weeks, gene expression of collagen 1?1 and decorin was increased on all mats compared to films. Expression of the tendon/ligament transcription factor scleraxis was suppressed on all electrospun mats relative to spin-coated films, but expression on the large-diameter fibre mats was consistently greater than on the medium-diameter fibre mats. These results suggest that larger-diameter fibres (e.g. > 2?µm) may be more suitable for in vitro development of a tendon/ligament tissue. PMID:23038413

Cardwell, Robyn D; Dahlgren, Linda A; Goldstein, Aaron S

2014-12-01

151

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

152

Classroom Dinosaur Dig  

NSDL National Science Digital Library

In this activity, learners participate in a simulated dig to discover fossilized dinosaur bones. Learners take notes, make a map and propose theories about dinosaurs. This can be used as a culminating activity at the end of a unit on dinosaurs, paleontology or archeology. This activity is featured on pp.48-50 (part of a lesson that begins on p.47) of the "Dinosphere" unit of study for grades 3-5.

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

2004-01-01

153

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.

154

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

155

Concise Review: Skeletal Muscle Stem Cells and Cardiac Lineage: Potential for Heart Repair  

PubMed Central

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

2014-01-01

156

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

157

Individual hematopoietic stem cells in human bone marrow of patients with aplastic anemia or myelodysplastic syndrome stably give rise to limited cell lineages.  

PubMed

Mutation of the phosphatidylinositol N-acetylglucosaminyltransferase subunit A (PIG-A) gene in hematopoietic stem cells (HSCs) results in the loss of glycosylphosphatidylinositol-anchored proteins (GPI-APs) on HSCs, but minimally affects their development, and thus can be used as a clonal maker of HSCs. We analyzed GPI-APs expression on six major lineage cells in a total of 574 patients with bone marrow (BM) failure in which microenvironment itself is thought to be unaffected, including aplastic anemia (AA) or myelodysplastic syndrome (MDS). GPI-APs-deficient (GPI-APs(-) ) cells were detected in 250 patients. Whereas the GPI-APs(-) cells were seen in all six lineages in a majority of patients who had higher proportion ([dbmtequ]3%) of GPI-APs(-) cells, they were detected in only limited lineages in 92.9% of cases in the lower proportion (<3%) group. In all 250 cases, the same lineages of GPI-APs(-) cells were detected even after 6-18-month intervals, indicating that the GPI-APs(-) cells reflect hematopoiesis maintained by a self-renewing HSC in most of cases. The frequency of clones with limited lineages seen in mild cases of AA was similar to that in severe cases, and clones with limited lineages were seen even in two health volunteer cases. These results strongly suggest most individual HSCs produce only restricted lineages even in a steady state. While this restriction could reflect heterogeneity in the developmental potential of HSCs, we propose an alternative model in which the BM microenvironment is mosaic in supporting commitment of progenitors toward distinct lineages. Our computer simulation based on this model successfully recapitulated the observed clinical data. PMID:23316019

Katagiri, Takamasa; Kawamoto, Hiroshi; Nakakuki, Takashi; Ishiyama, Ken; Okada-Hatakeyama, Mariko; Ohtake, Shigeki; Seiki, Yu; Hosokawa, Kohei; Nakao, Shinji

2013-03-01

158

Fossilized Dinosaur Teeth Adaptations  

NSDL National Science Digital Library

In this activity, learners use models of fossilized dinosaur teeth to understand how dinosaur teeth were used. Learners specifically research Tyrannosaurus rex and Triceratops horridus dinosaurs and determine that Triceratops teeth work the way pliers and scissors operate, and T. rex teeth are like sharp knives. Learners match and sort dinosaurs by the type and use of their teeth. This activity is featured on pp.14-18 (part of a lesson that begins on p.7) of the "Dinosphere" unit of study for grades 3-5.

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

2004-01-01

159

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.

160

What Is a Dinosaur?  

NSDL National Science Digital Library

In this classroom activity, young students learn what distinguishes dinosaurs from other animals. The activity opens with background information for teachers about these prehistoric reptiles. Working in small groups, students look through dinosaur books to gather interesting facts to share. As a class, students use their facts to create a semantic map. Then they explore the differences in dinosaur and lizard legs, and examine how these differences affect their stances. The activity concludes with a student worksheet that challenges them to identify the dinosaurs within a collection of animal illustrations.

161

Transcriptomic and phenotypic analysis of murine embryonic stem cell derived BMP2+ lineage cells: an insight into mesodermal patterning  

PubMed Central

Background Bone morphogenetic protein (BMP)2 is a late mesodermal marker expressed during vertebrate development and plays a crucial role in early embryonic development. The nature of the BMP2-expressing cells during the early stages of embryonic development, their transcriptome and cell phenotypes developed from these cells have not yet been characterized. Results We generated a transgenic BMP2 embryonic stem (ES) cell lineage expressing both puromycin acetyltransferase and enhanced green fluorescent protein (EGFP) driven by the BMP2 promoter. Puromycin resistant and EGFP positive BMP2+ cells with a purity of over 93% were isolated. Complete transcriptome analysis of BMP2+ cells in comparison to the undifferentiated ES cells and the control population from seven-day-old embryoid bodies (EBs; intersection of genes differentially expressed between undifferentiated ES cells and BMP2+ EBs as well as differentially expressed between seven-day-old control EBs and BMP2+ EBs by t-test, p < 0.01, fold change >2) by microarray analysis led to identification of 479 specifically upregulated and 193 downregulated transcripts. Transcription factors, apoptosis promoting factors and other signaling molecules involved in early embryonic development are mainly upregulated in BMP2+ cells. Long-term differentiation of the BMP2+ cells resulted in neural crest stem cells (NCSCs), smooth muscle cells, epithelial-like cells, neuronal-like cells, osteoblasts and monocytes. Interestingly, development of cardiomyocytes from the BMP2+ cells requires secondary EB formation. Conclusion This is the first study to identify the complete transcriptome of BMP2+ cells and cell phenotypes from a mesodermal origin, thus offering an insight into the role of BMP2+ cells during embryonic developmental processes in vivo. PMID:17784959

Doss, Michael Xavier; Chen, Shuhua; Winkler, Johannes; Hippler-Altenburg, Rita; Odenthal, Margareta; Wickenhauser, Claudia; Balaraman, Sridevi; Schulz, Herbert; Hummel, Oliver; Hübner, Norbert; Ghosh-Choudhury, Nandini; Sotiriadou, Isaia; Hescheler, Jürgen; Sachinidis, Agapios

2007-01-01

162

Dual Small-Molecule Targeting of SMAD Signaling Stimulates Human Induced Pluripotent Stem Cells toward Neural Lineages  

PubMed Central

Incurable neurological disorders such as Parkinson’s disease (PD), Huntington’s disease (HD), and Alzheimer’s disease (AD) are very common and can be life-threatening because of their progressive disease symptoms with limited treatment options. To provide an alternative renewable cell source for cell-based transplantation and as study models for neurological diseases, we generated induced pluripotent stem cells (iPSCs) from human dermal fibroblasts (HDFs) and then differentiated them into neural progenitor cells (NPCs) and mature neurons by dual SMAD signaling inhibitors. Reprogramming efficiency was improved by supplementing the histone deacethylase inhibitor, valproic acid (VPA), and inhibitor of p160-Rho associated coiled-coil kinase (ROCK), Y-27632, after retroviral transduction. We obtained a number of iPS colonies that shared similar characteristics with human embryonic stem cells in terms of their morphology, cell surface antigens, pluripotency-associated gene and protein expressions as well as their in vitro and in vivo differentiation potentials. After treatment with Noggin and SB431542, inhibitors of the SMAD signaling pathway, HDF-iPSCs demonstrated rapid and efficient differentiation into neural lineages. Six days after neural induction, neuroepithelial cells (NEPCs) were observed in the adherent monolayer culture, which had the ability to differentiate further into NPCs and neurons, as characterized by their morphology and the expression of neuron-specific transcripts and proteins. We propose that our study may be applied to generate neurological disease patient-specific iPSCs allowing better understanding of disease pathogenesis and drug sensitivity assays. PMID:25207966

Wattanapanitch, Methichit; Klincumhom, Nuttha; Potirat, Porntip; Amornpisutt, Rattaya; Lorthongpanich, Chanchao; U-pratya, Yaowalak; Laowtammathron, Chuti; Kheolamai, Pakpoom; Poungvarin, Niphon; Issaragrisil, Surapol

2014-01-01

163

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

E-print Network

Name: UID: 1 GEOL 104 Dinosaurs: A Natural History Homework 3: Dinosaur Relationships DUE: Wed. Nov. Thyreophora 7. Ankylosauria 8. What is the hypothesized diet of the dinosaurs in the cladogram above ]. Extra Credit) The diet of the dinosaur shown above was most likely [ meat | plants ]. For questions 20

Holtz Jr., Thomas R.

164

GEOL 104 Dinosaurs: A Natural History Homework 5: Dinosaur Physiology  

E-print Network

Name: 1 GEOL 104 Dinosaurs: A Natural History Homework 5: Dinosaur Physiology DUE: Mon. Nov. 27th (Dinosaur) Radiation 5th (Mammal) Radiation Locality Pred/Prey ratio Locality Pred/Prey ratio Morrison 3.5% Wasatch 4.4% Cloverly 3.7% Chadron 5.4% Dinosaur Park 3.5% Harrison 4.3% Hell Creek 1

Holtz Jr., Thomas R.

165

EZH2 and KDM6A act as an epigenetic switch to regulate mesenchymal stem cell lineage specification.  

PubMed

The methyltransferase, Enhancer of Zeste homology 2 (EZH2), trimethylates histone 3 lysine 27 (H3K27me3) on chromatin and this repressive mark is removed by lysine demethylase 6A (KDM6A). Loss of these epigenetic modifiers results in developmental defects. We demonstrate that Ezh2 and Kdm6a transcript levels change during differentiation of multipotential human bone marrow-derived mesenchymal stem cells (MSC). Enforced expression of Ezh2 in MSC promoted adipogenic in vitro and inhibited osteogenic differentiation potential in vitro and in vivo, whereas Kdm6a inhibited adipogenesis in vitro and promoted osteogenic differentiation in vitro and in vivo. Inhibition of EZH2 activity and knockdown of Ezh2 gene expression in human MSC resulted in decreased adipogenesis and increased osteogenesis. Conversely, knockdown of Kdm6a gene expression in MSC leads to increased adipogenesis and decreased osteogenesis. Both Ezh2 and Kdm6a were shown to affect expression of master regulatory genes involved in adipogenesis and osteogenesis and H3K27me3 on the promoters of master regulatory genes. These findings demonstrate an important epigenetic switch centered on H3K27me3 which dictates MSC lineage determination. PMID:24123378

Hemming, Sarah; Cakouros, Dimitrios; Isenmann, Sandra; Cooper, Lachlan; Menicanin, Danijela; Zannettino, Andrew; Gronthos, Stan

2014-03-01

166

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 álamo, Juan C.; Chang, Zee-Fen; Tang, Ming-Jer; Khoo, Kay-Hooi; Kuo, Jean-Cheng

2014-01-01

167

Lineage potential, plasticity and environmental reprogramming of epithelial stem/progenitor cells.  

PubMed

Recent evidence supports and reinforces the concept that environmental cues may reprogramme somatic cells and change their natural fate. In the present review, we concentrate on environmental reprogramming and fate potency of different epithelial cells. These include stratified epithelia, such as the epidermis, hair follicle, cornea and oesophagus, as well as the thymic epithelium, which stands alone among simple and stratified epithelia, and has been shown recently to contain stem cells. In addition, we briefly discuss the pancreas as an example of plasticity of intrinsic progenitors and even differentiated cells. Of relevance, examples of plasticity and fate change characterize pathologies such as oesophageal metaplasia, whose possible cell origin is still debated, but has important implications as a pre-neoplastic event. Although much work remains to be done in order to unravel the full potential and plasticity of epithelial cells, exploitation of this phenomenon has already entered the clinical arena, and might provide new avenues for future cell therapy of these tissues. PMID:24849231

Amici, Alessandro W; Onikoyi, Fatai O; Bonfanti, Paola

2014-06-01

168

From weird wonders to stem lineages: the second reclassification of the Burgess Shale fauna.  

PubMed

The Burgess Shale, a set of fossil beds containing the exquisitely preserved remains of marine invertebrate organisms from shortly after the Cambrian explosion, was discovered in 1909, and first brought to widespread popular attention by Stephen Jay Gould in his 1989 bestseller Wonderful life: The Burgess Shale and the nature of history. Gould contrasted the initial interpretation of these fossils, in which they were 'shoehorned' into modern groups, with the first major reexamination begun in the 1960s, when the creatures were perceived as 'weird wonders', possessing unique body plans and unrelated to modern organisms. More recently, a third phase of Burgess Shale studies has arisen, which has not yet been historically examined. This third phase represents a revolutionary new understanding, brought about, I believe, by a change in taxonomic methodology that led to a new perception of the Burgess creatures, and a new way to comprehend their relationships with modern organisms. The adoption of cladistics, and its corollary, the stem group concept, has forged a new understanding of the Burgess Shale ... but has it also changed the questions we are allowed to ask about evolution? PMID:18761282

Brysse, Keynyn

2008-09-01

169

Dinosaur Extinction, Early Childhood Style  

ERIC Educational Resources Information Center

Do dinosaurs have bellybuttons? This intriguing question launched a journey into inquiry science that captivated a class of four-year-olds for eight months. As students enjoyed dinosaur books, examined dinosaur artifacts, drew pictures, watched videos, and generally immersed themselves in all things dinosaur, the authors built a culture of…

Murray, Mary; Valentine-Anand, Lesley

2008-01-01

170

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

171

Proposal on Dinosaur Extinction  

Microsoft Academic Search

The extinction of the dinosaurs is an import issue that can shed light on the repeated occurrences of mass extinctions .It is very important that we don't blindly accept theories because they are lavish and extravagant. Our aim is to show that dinosaurs didn't die out due one catastrophic celestial event. On the contrary we intend to prove that their

Chirag Shah; Viren Amin; Harit Desai

172

In search of rat stem Leydig cells: Identification, isolation, and lineage-specific development  

PubMed Central

Leydig cells (LCs) are thought to differentiate from spindle-shaped precursor cells that exhibit some aspects of differentiated function, including 3?-hydroxysteroid dehydrogenase (3?HSD) activity. The precursor cells ultimately derive from undifferentiated stem LCs (SLCs), which are postulated to be present in testes before the onset of precursor cell differentiation. We searched for cells in the neonatal rat testis with the abilities to: (i) proliferate and expand indefinitely in vitro (self renew); (ii) differentiate (i.e., 3?HSD and ultimately synthesize testosterone); and (iii) when transplanted into host rat testes, colonize the interstitium and subsequently differentiate in vivo. At 1 week postpartum, spindle-shaped cells were seen in the testicular interstitium that differed from the precursor cells in that they were 3?HSD-negative, luteinizing hormone (LH) receptor (LHR)-negative, and platelet-derived growth factor receptor ? (PDGFR?)-positive. These cells were purified from the testes of 1-week-old rats. The cells contained proteins known to be involved in LC development, including GATA4, c-kit receptor, and leukemia inhibitory factor receptor. The putative SLCs expanded over the course of 6 months while remaining undifferentiated. When treated in media that contained thyroid hormone, insulin-like growth factor I, and LH, 40% of the putative SLCs came to express 3?HSD and to synthesize testosterone. When transplanted into host rat testes from which LCs had been eliminated, the putative SLCs colonized the interstitium and subsequently expressed 3?HSD, demonstrating their ability to differentiate in vivo. We conclude that these cells are likely to be the sought-after SLCs. PMID:16467141

Ge, Ren-Shan; Dong, Qiang; Sottas, Chantal M.; Papadopoulos, Vassilios; Zirkin, Barry R.; Hardy, Matthew P.

2006-01-01

173

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

174

Dinosaur physiology. Evidence for mesothermy in dinosaurs.  

PubMed

Were dinosaurs ectotherms or fast-metabolizing endotherms whose activities were unconstrained by temperature? To date, some of the strongest evidence for endothermy comes from the rapid growth rates derived from the analysis of fossil bones. However, these studies are constrained by a lack of comparative data and an appropriate energetic framework. Here we compile data on ontogenetic growth for extant and fossil vertebrates, including all major dinosaur clades. Using a metabolic scaling approach, we find that growth and metabolic rates follow theoretical predictions across clades, although some groups deviate. Moreover, when the effects of size and temperature are considered, dinosaur metabolic rates were intermediate to those of endotherms and ectotherms and closest to those of extant mesotherms. Our results suggest that the modern dichotomy of endothermic versus ectothermic is overly simplistic. PMID:24926017

Grady, John M; Enquist, Brian J; Dettweiler-Robinson, Eva; Wright, Natalie A; Smith, Felisa A

2014-06-13

175

G9a/GLP-dependent histone H3K9me2 patterning during human hematopoietic stem cell lineage commitment  

PubMed Central

G9a and GLP are conserved protein methyltransferases that play key roles during mammalian development through mono- and dimethylation of histone H3 Lys 9 (H3K9me1/2), modifications associated with transcriptional repression. During embryogenesis, large H3K9me2 chromatin territories arise that have been proposed to reinforce lineage choice by affecting high-order chromatin structure. Here we report that in adult human hematopoietic stem and progenitor cells (HSPCs), H3K9me2 chromatin territories are absent in primitive cells and are formed de novo during lineage commitment. In committed HSPCs, G9a/GLP activity nucleates H3K9me2 marks at CpG islands and other genomic sites within genic regions, which then spread across most genic regions during differentiation. Immunofluorescence assays revealed the emergence of H3K9me2 nuclear speckles in committed HSPCs, consistent with progressive marking. Moreover, gene expression analysis indicated that G9a/GLP activity suppresses promiscuous transcription of lineage-affiliated genes and certain gene clusters, suggestive of regulation of HSPC chromatin structure. Remarkably, HSPCs continuously treated with UNC0638, a G9a/GLP small molecular inhibitor, better retain stem cell-like phenotypes and function during in vitro expansion. These results suggest that G9a/GLP activity promotes progressive H3K9me2 patterning during HSPC lineage specification and that its inhibition delays HSPC lineage commitment. They also inform clinical manipulation of donor-derived HSPCs. PMID:23105005

Chen, Xiaoji; Skutt-Kakaria, Kyobi; Davison, Jerry; Ou, Yang-Li; Choi, Edward; Malik, Punam; Loeb, Keith; Wood, Brent; Georges, George; Torok-Storb, Beverly; Paddison, Patrick J.

2012-01-01

176

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

177

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

178

Continuing differentiation of human mesenchymal stem cells and induced chondrogenic and osteogenic lineages in electrospun PLGA nanofiber scaffold  

PubMed Central

Nanofibers have recently gained substantial interest for potential applications in tissue engineering. The objective of this study was to determine whether electrospun nanofibers accommodate the viability, growth, and differentiation of human mesenchymal stem cells (hMSCs) as well as their osteogenic (hMSC-Ob) and chondrogenic (hMSC-Ch) derivatives. Poly(D,L-lactide-co-glycolide) (PLGA) beads with a PLA:PGA ratio of 85:15 were electrospun into non-woven fibers with an average diameter of 760±210 nm. The average Young’s modulus of electrospun PLGA nanofibers was 42±26 kPa, per nanoindentation with atomic force microscopy (AFM). Human MSCs were seeded 1–4 weeks at a density of 2×106 cells/mL in PLGA nanofiber sheets. After 2 week culture on PLGA nanofiber scaffold, hMSCs remained as precursors upon immunoblotting with hKL12 antibody. SEM taken up to 7 days after cell seeding revealed that hMSCs, hMSC-Ob and hMSC-Ch apparently attached to PLGA nanofibers. The overwhelming majority of hMSCs was viable and proliferating in PLGA nanofiber scaffolds up to the tested 14 days, as assayed live/dead tests, DNA assay and BrdU. In a separate experiment, hMSCs seeded in PLGA nanofiber scaffolds were differentiated into chodrogenic and osteogenic cells. Histological assays revealed that hMSCs continuously differentiated into chondrogenic cells and osteogenic cells after 2 week incubation in PLGA nanofibers. Taken together, these data represent an original investigation of continuous differentiation of hMSCs into chondrogenic and osteogenic cells in PLGA nanofiber scaffold. Consistent with previous work, these findings also suggest that nanofibers may serve as accommodative milieu for not only hMSCs, but also as a 3D carrier vehicle for lineage specific cells. PMID:17010425

Xin, Xuejun; Hussain, Mohammad; Mao, Jeremy J.

2010-01-01

179

Body composition changes and inhibition of fat development in vivo implicates androgen in regulation of stem cell lineage allocation  

PubMed Central

Androgens regulate body composition in youth and declining testosterone that occurs with aging is associated with muscle wasting, increased fat mass and osteopenia. Transgenic mice with targeted androgen receptor (AR) overexpression in mesenchymal stem cells (MSC) were generated to explore the role of androgen signaling in the regulation of body composition. Transgenic males, but not females, were shorter and have reduced body weight and visceral fat accumulation. Dual energy x-ray absorptiometry (DXA) revealed significant reductions in fat mass with a reciprocal increase in lean mass, yet no difference in food consumption or locomotor activity was observed. Adipose tissue weight was normal in brown fat but reduced in both gonadal and perirenal depots, and reduced hyperplasia was observed with smaller adipocyte size in visceral and subcutaneous white adipose tissue. Although serum leptin, adiponectin, triglyceride, and insulin levels were no different between the genotypes, intraperitoneal glucose tolerance testing showed improved glucose clearance in transgenic males. High levels of the AR transgene are detected in MSCs but not in mature fat tissue. Reduced fibroblast colony forming units indicate fewer progenitor cells resident in the marrow in vivo. Precocious expression of GLUT4, PPAR? and C/EBP? was observed in proliferating precursor cultures from transgenic mice compared to controls. In more mature cultures, there was little difference between the genotypes. We propose a mechanism where enhanced androgen sensitivity can alter lineage commitment in vivo to reduce progenitor number and fat development, while increasing the expression of key factors to promote smaller adipocytes with improved glucose clearance. PMID:21381083

Semirale, Anthony A.; Zhang, Xiaowei; Wiren, Kristine M.

2011-01-01

180

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

PubMed

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

2012-06-01

181

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

182

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

183

Warm and Cool Dinosaurs.  

ERIC Educational Resources Information Center

Presents an art activity in which first grade students draw dinosaurs in order to learn about the concept of warm and cool colors. Explains how the activity also helped the students learn about the concept of distance when drawing. (CMK)

Mannlein, Sally

2001-01-01

184

Fossilized Dinosaur Bones  

NSDL National Science Digital Library

This slide show presents images of dinosaur bones and shows paleotologists at work excavating and preserving these fossils, the best evidence remaining of these long-lost creatures. A background essay and discussion questons are included.

185

Dinosaur Reproduction and Parenting  

NASA Astrophysics Data System (ADS)

Non-avian dinosaur reproductive and parenting behaviors were mostly similar to those of extant archosaurs. Non-avian dinosaurs were probably sexually dimorphic and some may have engaged in hierarchical rituals. Non-avian coelurosaurs (e.g. Troodontidae, Oviraptorosauria) had two active oviducts, each of which produced single eggs on a daily or greater time scale. The eggs of non-coelurosaurian dinosaurs (e.g. Ornithischia, Sauropoda) were incubated in soils, whereas the eggs of non-avian coelurosaurs (e.g. Troodon, Oviraptor) were incubated with a combination of soil and direct parental contact. Parental attention to the young was variable, ranging from protection from predators to possible parental feeding of nest-bound hatchlings. Semi-altricial hadrosaur hatchlings exited their respective nests near the time of their first linear doubling. Some reproductive behaviors, once thought exclusive to Aves, arose first in non-avian dinosaurs. The success of the Dinosauria may be related to reproductive strategies.

Horner, John R.

186

Blastema cells derived from New Zealand white rabbit's pinna carry stemness properties as shown by differentiation into insulin producing, neural, and osteogenic lineages representing three embryonic germ layers.  

PubMed

Stem cells (SCs) are known as undifferentiated cells with self-renewal and differentiation capacities. Regeneration is a phenomenon that occurs in a limited number of animals after injury, during which blastema tissue is formed. It has been hypothesized that upon injury, the dedifferentiation of surrounding tissues leads into the appearance of cells with SC characteristics. In present study, stem-like cells (SLCs) were obtained from regenerating tissue of New Zealand white rabbit's pinna and their stemness properties were examined by their capacity to differentiate toward insulin producing cells (IPCs), as well as neural and osteogenic lineages. Differentiation was induced by culture of SLCs in defined medium, and cell fates were monitored by specific staining, RT-PCR and flow cytometry assays. Our results revealed that dithizone positive cells, which represent IPCs, and islet-like structures appeared 1 week after induction of SLCs, and this observation was confirmed by the elevated expression of Ins, Pax6 and Glut4 at mRNA level. Furthermore, SLCs were able to express neural markers as early as 1 week after retinoic acid treatment. Finally, SLCs were able to differentiate into osteogenic lineage, as confirmed by Alizarin Red S staining and RT-PCR studies. In conclusion, SLCs, which could successfully differentiate into cells derived from all three germ layers, can be considered as a valuable model to study developmental biology and regenerative medicine. PMID:25371011

Saeinasab, Morvarid; Matin, Maryam M; Rassouli, Fatemeh B; Bahrami, Ahmad Reza

2014-11-01

187

A self-limiting switch based on translational control regulates the transition from proliferation to differentiation in an adult stem cell lineage  

PubMed Central

Summary In adult stem cell lineages, progenitor cells commonly undergo mitotic transit amplifying (TA) divisions before terminal differentiation, allowing production of many differentiated progeny per stem cell division. Mechanisms that limit TA divisions and trigger the switch to differentiation may protect against cancer by preventing accumulation of oncogenic mutations in the proliferating population. Here we show that the switch from TA proliferation to differentiation in the Drosophila male germline stem cell lineage is mediated by translational control. The TRIM-NHL tumor suppressor homolog Mei-P26 facilitates accumulation of the differentiation regulator Bam in TA cells. In turn, Bam and its partner Bgcn bind the mei-P26 3?UTR and repress translation of mei-P26 in late TA cells. Thus, germ cells progress through distinct, sequential regulatory states, from Mei-P26 on/Bam off to Bam on/Mei-P26 off. TRIM-NHL homologs across species facilitate the switch from proliferation to differentiation, suggesting a novel and conserved developmentally-programmed tumor suppressor mechanism. PMID:23122292

Insco, Megan L.; Bailey, Alexis S.; Kim, Jongmin; Olivares, Gonzalo H.; Wapinski, Orly L.; Tam, Cheuk Ho; Fuller, Margaret T.

2012-01-01

188

The Bristol Dinosaur Project  

Microsoft Academic Search

Dinosaurs have been fascinating to the widest public since the 1840s, and that interest has grown step-wise ever since. Public interest has been harnessed over the years especially by museums in blockbuster exhibitions, and in the form of best-selling books and films. Here we describe a major educational initiative, the Bristol Dinosaur Project, which has run for ten years and

Michael J. Benton; Remmert Schouten; Edward J. A. Drewitt; Pedro Viegas

189

346 expression of imprinted noncoding RNA from the dlk1-dio3 locus in human embryonic stem cells advantages neural lineage differentiation.  

PubMed

Pluripotent stem cells are increasingly used for therapeutic models, including transplantation of neural progenitors derived from human embryonic stem cells (hESC). Recently, long noncoding RNA (lncRNA), including Maternally Expressed Gene 3 (MEG3) derived from the DLK1-DIO3-imprinted locus, were found to be expressed during neural developmental events. Their deregulations are associated with various neurological diseases. The DLK1-DIO3-imprinted locus encodes abundant noncoding RNA (ncRNA) that are regulated by differential methylation on the locus. The aim of our research was to study the correlation between the DLK1-DIO3-derived ncRNA and the capacity of hESC neural lineage differentiation. We classified hESC into MEG3-ON and MEG3-OFF based on the expression levels of MEG3 as well as its downstream microRNA by qRT-PCR. Initial embryoid body (EB) formation was conducted to examine the 3 germ layer's differentiation ability. Complementary DNA microarray was used to analyse the gene expression profiles of hESC. Directed neural lineage differentiation was performed, followed by analysis of neural lineage marker expression levels and neurite formation via qRT-PCR and immunocytochemistry methods to investigate the capacity of neural differentiation in MEG3-ON and MEG3-OFF hESC. As for statistics, error bars indicate standard error of the mean. Student's t-test was used for calculating P-values, and a P-value of less than 0.05 was considered to be significant. Our results showed that MEG3-ON and MEG3-OFF hESC differed greatly in DLK1-DIO3-derived ncRNA expression levels, but had comparable pluripotency gene expression profiles. Genes related to nervous system development and neural cancers were differentially expressed in MEG3-OFF hESC, where DLK1-DIO3-derived ncRNA were repressed compared to MEG3-ON ones before differentiation. In neural lineage-like cells derived from MEG3-OFF hESC, lower expression levels of neural lineage markers and impaired neurite formation were observed compared to MEG3-ON hESC at the same time points after differentiation. We suggest that the expression of DLK1-DIO3-derived lncRNA, MEG3, can be used as a simple and effective screening criterion for identifying MEG3-ON hESC with activation of DLK1-DIO3-imprinted ncRNA as starting materials to benefit neural lineage-associated studies. PMID:25472394

Mo, C-F; Wu, F-C; Tai, K-Y T; Chang, W-C; Chang, K-W; Kuo, H-C; Ho, H-N; Chen, H-F; Lin, S-P

2014-12-01

190

Dinosaur Extinction, Early Childhood Style  

NSDL National Science Digital Library

Do dinosaurs have bellybuttons? This intriguing question launched a journey into inquiry science that captivated a class of four-year-olds for eight months. As students enjoyed dinosaur books, examined dinosaur artifacts, drew pictures, watched videos, and generally immersed themselves in all things dinosaur, the authors built a culture of learning in their classroom that helped these young students develop science-process skills such as observation, measurement, and communication. They share their inspiring learning adventure here.

Lesley Valentine-Anand

2008-12-01

191

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.

192

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

193

Dinosaurs in Russia and Mongolia  

E-print Network

The Age of Dinosaurs in Russia and Mongolia EDITED BY MichaelJ. Bemon University of Bristol Mikhail the CloetaCeous of Russia, Middle Asia, and :rvlongolia, arc equally important. Some of the dinosaurs elsewhere, but these are sorely in need of revision (see Chapter 11). The dinosaurs and other tetrapods from

Benton, Michael

194

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

195

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

196

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.

197

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

198

A Child Centered Approach to Dinosaurs.  

ERIC Educational Resources Information Center

Describes a curriculum for teaching young children about dinosaurs. Activity topics included Diplodocus eggs, sorting dinosaurs, creating terrariums, and extinction. Describes the incorporation of dinosaur activities into other subject areas and resource materials. (RJC)

Strader, William H.; Rinker, Catherine A.

1989-01-01

199

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; Lourenço, Tânia; dos Santos, Francisco; Andrade, Pedro Z.; Cardoso, Carla M. P.; Vieira, Margarida; Paiva, Artur; da Silva, Cláudia L.; Cabral, Joaquim M. S.; Relvas, João B.; Grãos, Mário

2014-01-01

200

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

201

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

202

Kindergartners Love Dinosaurs  

ERIC Educational Resources Information Center

In this article, the author relates how she uses an art lesson that integrates art, language arts, and science in an enjoyable, creative project about dinosaurs in her kindergarten class. She relates how the children enjoy being illustrators and becoming familiar with well-known children's illustrators. She also relates that she starts her classes…

Stollon, Marcy

2005-01-01

203

Universal hydraulics of the flowering plants: vessel diameter scales with stem length across angiosperm lineages, habits and climates.  

PubMed

Angiosperm hydraulic performance is crucially affected by the diameters of vessels, the water conducting conduits in the wood. Hydraulic optimality models suggest that vessels should widen predictably from stem tip to base, buffering hydrodynamic resistance accruing as stems, and therefore conductive path, increase in length. Data from 257 species (609 samples) show that vessels widen as predicted with distance from the stem apex across angiosperm orders, habits and habitats. Standardising for stem length, vessels are only slightly wider in warm/moist climates and in lianas, showing that, rather than climate or habit, plant size is by far the main driver of global variation in mean vessel diameter. Terminal twig vessels become wider as plant height increases, while vessel density decreases slightly less than expected tip to base. These patterns lead to testable predictions regarding evolutionary strategies allowing plants to minimise carbon costs per unit leaf area even as height increases. PMID:24847972

Olson, Mark E; Anfodillo, Tommaso; Rosell, Julieta A; Petit, Giai; Crivellaro, Alan; Isnard, Sandrine; León-Gómez, Calixto; Alvarado-Cárdenas, Leonardo O; Castorena, Matiss

2014-08-01

204

Aconiti Lateralis Preparata Radix Activates the Proliferation of Mouse Bone Marrow Mesenchymal Stem Cells and Induces Osteogenic Lineage Differentiation through the Bone Morphogenetic Protein-2/Smad-Dependent Runx2 Pathway  

PubMed Central

Mesenchymal stem cells have the capacity for self-renewal and under appropriate stimulation give rise to osteogenic, adipogenic, and chondrogenic lineages. To advance the clinical use of stem cell therapy, such as stem cell transplantation, it is important to find substances that promote endogenous stem cell proliferation and differentiation. We investigated whether medicinal herbs have the potential to promote stem cell proliferation and differentiation, using a cell cycle analysis and differentiation assay. We found that Aconiti Lateralis Preparata Radix (ALR) promoted the proliferation rate of mouse bone marrow mesenchymal stem cells (mBMMSCs) up to 122.24% compared to untreated cells. Fluorescence-activated cell sorter analysis showed that the percentage of cells in the G2/M phase increased to 17.33% in ALR-treated cells compared to 5.65% in normal cells. Signaling pathway analysis indicated that this was mediated through the extracellular signal-regulated kinase 1/2 pathway. A differentiation assay showed that ALR induced differentiation of mBMMSCs into an osteogenic lineage 2 weeks after treatment, whereas traditional osteogenic induction medium treatment did not promote differentiation for 3 weeks. This osteogenic differentiation was signaled by the bone morphogenetic protein-2/Smad-dependent Runx2 pathway. We found that ALR could promote mBMMSC proliferation and differentiation into the osteogenic lineage. PMID:23983792

Park, Jae Kwang; Park, Seong Kyu; Chang, Mun Seog

2013-01-01

205

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

206

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.

207

What's in a Dinosaur Name?  

NSDL National Science Digital Library

In this activity, learners explore the etymology of dinosaur names. Learners first discuss how dinosaurs are often named after a body part or behavior, where they were found, or a person (finder or famous). Learners also discuss Greek and Latin prefixes and suffixes that are commonly found in dinosaur names. Then, learners create a paper puzzle that generates new dinosaur names. This activity is featured on pp.20-27 (part of a lesson that begins on p.19) of the "Dinosphere" unit of study for grades 3-5.

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

2004-01-01

208

Dinosaur Fossils Predict Body Temperatures  

E-print Network

Perhaps the greatest mystery surrounding dinosaurs concerns whether they were endotherms, ectotherms, or some unique intermediate form. Here we present a model that yields estimates of dinosaur body temperature based on ontogenetic growth trajectories obtained from fossil bones. The model predicts that dinosaur body temperatures increased with body mass from approximately 25 8C at 12 kg to approximately 41 8C at 13,000 kg. The model also successfully predicts observed increases in body temperature with body mass for extant crocodiles. These results provide direct evidence that dinosaurs were reptiles that exhibited inertial homeothermy.

James F. Gillooly; Andrew P. Allen; Eric L. Charnov

209

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.

Andrew Heckert

210

A bizarre Cretaceous theropod dinosaur from Patagonia and the evolution of Gondwanan dromaeosaurids.  

PubMed

Fossils of a predatory dinosaur provide novel information about the evolution of unenlagiines, a poorly known group of dromaeosaurid theropods from Gondwana. The new dinosaur is the largest dromaeosaurid yet discovered in the Southern Hemisphere and depicts bizarre cranial and postcranial features. Its long and low snout bears numerous, small-sized conical teeth, a condition resembling spinosaurid theropods. Its short forearms depart from the characteristically long-armed condition of all dromaeosaurids and their close avian relatives. The new discovery amplifies the range of morphological disparity among unenlagiines, demonstrating that by the end of the Cretaceous this clade included large, short-armed forms alongside crow-sized, long-armed, possibly flying representatives. The new dinosaur is the youngest record of dromaeosaurids from Gondwana and represents a previously unrecognized lineage of large predators in Late Cretaceous dinosaur faunas mainly dominated by abelisaurid theropods. PMID:19129109

Novas, Fernando E; Pol, Diego; Canale, Juan I; Porfiri, Juan D; Calvo, Jorge O

2009-03-22

211

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

212

Hematopoiesis in steady-state versus stress: self-renewal, lineage fate choice, and the conversion of danger signals into cytokine signals in hematopoietic stem cells.  

PubMed

Long-term hematopoietic stem cells (LT-HSCs) replenish the innate and adaptive immune compartments throughout life. Although significant progress has defined the major transcription factors that regulate lineage specification, the architectural proteins that globally coordinate DNA methylation, histone modification, and changes in gene expression are poorly defined. Provocative new studies establish the chromatin organizer special AT-rich binding protein 1 (Satb1) as one such global regulator in LT-HSCs. Satb1 is a nuclear organizer that partitions chromatin through the formation of cage-like structures. By integrating epigenetic and transcriptional pathways, Satb1 coordinates LT-HSC division, self-renewal, and lymphoid potential. Unexpected among the assortment of genes under Satb1 control in hematopoietic stem cells (HSCs) are cytokines, a finding that takes on additional importance with the provocative finding that short-term HSCs and downstream multipotent progenitors are potent and biologically relevant cytokine secretors during stress-mediated hematopoiesis. Together, these studies reveal a new mechanism of fate regulation and an unforeseen functional capability of HSCs. PMID:25128551

Borghesi, Lisa

2014-09-01

213

BRACHYURY and CDX2 mediate BMP-induced differentiation of human and mouse pluripotent stem cells into embryonic and extraembryonic lineages.  

PubMed

BMP is thought to induce hESC differentiation toward multiple lineages including mesoderm and trophoblast. The BMP-induced trophoblast phenotype is a long-standing paradox in stem cell biology. Here we readdressed BMP function in hESCs and mouse epiblast-derived cells. We found that BMP4 cooperates with FGF2 (via ERK) to induce mesoderm and to inhibit endoderm differentiation. These conditions induced cells with high levels of BRACHYURY (BRA) that coexpressed CDX2. BRA was necessary for and preceded CDX2 expression; both genes were essential for expression not only of mesodermal genes but also of trophoblast-associated genes. Maximal expression of the latter was seen in the absence of FGF but these cells coexpressed mesodermal genes and moreover they differed in cell surface and epigenetic properties from placental trophoblast. We conclude that BMP induces human and mouse pluripotent stem cells primarily to form mesoderm, rather than trophoblast, acting through BRA and CDX2. PMID:21816365

Bernardo, Andreia S; Faial, Tiago; Gardner, Lucy; Niakan, Kathy K; Ortmann, Daniel; Senner, Claire E; Callery, Elizabeth M; Trotter, Matthew W; Hemberger, Myriam; Smith, James C; Bardwell, Lee; Moffett, Ashley; Pedersen, Roger A

2011-08-01

214

Dinosaurs in Patagonia  

NSDL National Science Digital Library

This Web site is a firsthand report from an expedition to Patagonia in which the first dinosaur embryos with fossilized skin were found. It tells the story of the find, which was made by scientists who were actually looking for early birds and their ancestors. There are two short English and Spanish audio recordings. A select list of books and articles by the expedition's two lead scientists, including abstracts of and excerpts from their work is included.

215

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.

216

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.

Lawrence Hall of Science

2005-01-01

217

The Saurischian Dinosaurs  

NSDL National Science Digital Library

This description of the saurischian or "lizard-hipped" dinosaurs discusses the major characteristics that distinguish saurischians from other tetrapods that also have pelves (hips) composed of three elements: the ilium, ischium, and pubis. These are a grasping hand, asymmetrical fingers, a long, mobile neck, and a pubis that points downward and forward at an angle to the ischium. There is also a clarification of the "bird-hipped" designation.

218

Lineage tracing reveals multipotent stem cells maintain human adenomas and the pattern of clonal expansion in tumor evolution  

PubMed Central

The genetic and morphological development of colorectal cancer is a paradigm for tumorigenesis. However, the dynamics of clonal evolution underpinning carcinogenesis remain poorly understood. Here we identify multipotential stem cells within human colorectal adenomas and use methylation patterns of nonexpressed genes to characterize clonal evolution. Numerous individual crypts from six colonic adenomas and a hyperplastic polyp were microdissected and characterized for genetic lesions. Clones deficient in cytochrome c oxidase (CCO?) were identified by histochemical staining followed by mtDNA sequencing. Topographical maps of clone locations were constructed using a combination of these data. Multilineage differentiation within clones was demonstrated by immunofluorescence. Methylation patterns of adenomatous crypts were determined by clonal bisulphite sequencing; methylation pattern diversity was compared with a mathematical model to infer to clonal dynamics. Individual adenomatous crypts were clonal for mtDNA mutations and contained both mucin-secreting and neuroendocrine cells, demonstrating that the crypt contained a multipotent stem cell. The intracrypt methylation pattern was consistent with the crypts containing multiple competing stem cells. Adenomas were epigenetically diverse populations, suggesting that they were relatively mitotically old populations. Intratumor clones typically showed less diversity in methylation pattern than the tumor as a whole. Mathematical modeling suggested that recent clonal sweeps encompassing the whole adenoma had not occurred. Adenomatous crypts within human tumors contain actively dividing stem cells. Adenomas appeared to be relatively mitotically old populations, pocketed with occasional newly generated subclones that were the result of recent rapid clonal expansion. Relative stasis and occasional rapid subclone growth may characterize colorectal tumorigenesis. PMID:23766371

Humphries, Adam; Cereser, Biancastella; Gay, Laura J.; Miller, Daniel S. J.; Das, Bibek; Gutteridge, Alice; Elia, George; Nye, Emma; Jeffery, Rosemary; Poulsom, Richard; Novelli, Marco R.; Rodriguez-Justo, Manuel; McDonald, Stuart A. C.; Wright, Nicholas A.; Graham, Trevor A.

2013-01-01

219

If You Were a Dinosaur...  

ERIC Educational Resources Information Center

Dinosaurs are one of those science topics that draw children in and teach them about concepts like measuring and using descriptive language. Learning about dinosaurs, although not hands-on like observing and recording caterpillar growth, develops critical thinking and introduces animal diversity and the relations between body form and function.…

Ashbrook, Peggy

2010-01-01

220

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

221

Did Man Live With Dinosaurs?  

E-print Network

Even though many evolutionists will tell you that people and dinosaurs never lived together, and that dinosaurs went extinct a long time ago, there is a lot of proof not only that people and dinosaurs co-existed, but that there are dinosaurs alive today. Cave drawings, historical literature, and fossils all show man and dinosaurs living together. An examination of these facts will show that people and dinosaurs co-existed. First, let us look at cave drawings. There have been many cave drawings found in places such as the Grand Canyon, in ravines, various caves, and other places. In Natural Bridges State Park, there are petroglyphs depicting dinosaur-like animals by the Anazi Indians, 400-1500 A.D. An Indian pictograph found in the Havasupai Canyon in the Grand Canyon shows men hunting dinosaurs. People have found stones with similar, but much more detailed, motifs. These stones are found in Ica, Peru, are about the size of bowling balls, appear to be made of granite, and have a polished look. One of the

Brooke Lodien

222

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

223

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

224

Dinosaur's Sex No Longer a Mystery  

NSDL National Science Digital Library

Dinosaur researchers have achieved another first: discovering a way to tell the sex of a dinosaur. The secret is in the bone. This radio broadcast reports on the discovery of medullary bone in dinosaurs, which exists in a cavity of the thigh bone in egg-laying female therapod dinosaurs and provides calcium for the shells of eggs. This discovery also further links dinosaurs to birds. The clip is 3 minutes and 41 seconds in length.

225

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

226

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

227

Notch signaling activation in human embryonic stem cells is required for embryonic but not trophoblastic lineage commitment  

PubMed Central

Summary The Notch signaling pathway plays important roles in cell fate determination during embryonic development and adult life. In this study, we focus on the role of Notch signaling in governing cell fate choices in human embryonic stem (hES) cells. Using genetic and pharmacological approaches, we achieved both blockade and conditional activation of Notch signaling in several hES cell lines. We report here that activation of Notch signaling is required for undifferentiated hES cells to form the progeny of all three embryonic germ layers, but not trophoblast cells. In addition, transient Notch signaling pathway activation enhanced generation of hematopoietic cells from committed hES cells. These new insights into the roles of Notch in hES cell fate determination may help to efficiently direct hES cell differentiation into therapeutically relevant cell types. PMID:18462696

Yu, Xiaobing; Zou, Jizhong; Ye, Zhaohui; Hammond, Holly; Chen, Guibin; Tokunaga, Akinori; Mali, Prashant; Li, Yue-Ming; Civin, Curt; Gaiano, Nicholas; Cheng, Linzhao

2008-01-01

228

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

229

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.

230

Adipose-derived stem cell adhesion on laminin-coated microcarriers improves commitment toward the cardiomyogenic lineage.  

PubMed

For tissue-engineering studies of the infarcted heart it is essential to identify a source of cells that may provide cardiomyocyte progenitors, which is easy to amplify, accessible in adults, and allowing autologous grafts. Preclinical studies have shown that human adipose-derived stem cells (ADSCs) can differentiate into cardiomyocyte-like cells and improve heart function in myocardial infarction. We have developed pharmacologically active microcarriers (PAMs) which are biodegradable and biocompatible polymeric microspheres conveying cells on their biomimetic surface, therefore providing an adequate three-dimensional (3D) microenvironment. Moreover, they can release a growth factor in a prolonged manner. In order to implement ADSCs and PAMs for cardiac tissue engineering we first defined the biomimetic surface by studying the influence of matrix molecules laminin (LM) and fibronectin (FN), in combination with growth factors present in the cardiogenic niche, to further enhance the in vitro cardiac differentiation of ADSCs. We demonstrated that LM increased the expression of cardiac markers (Nkx2.5, GATA4, MEF2C) by ADSCs after 2 weeks in vitro. Interestingly, our results suggest that the 3D support provided by PAMs with a LM biomimetic surface (LM-PAMs) further enhanced the expression of cardiac markers and induced the expression of a more mature contractile protein, cardiac troponin I, compared with the 2D differentiating conditions after only 1 week in culture. The enrichment of the growth-factor cocktail with TGF-?1 potentiated the cardiomyogenic differentiation. These results suggest that PAMs offering a LM biomimetic surface may be efficiently used for applications combining adult stem cells in tissue-engineering strategies of the ischemic heart. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014. PMID:25098676

Karam, Jean-Pierre; Bonafè, Francesca; Sindji, Laurence; Muscari, Claudio; Montero-Menei, Claudia N

2014-08-01

231

Eltrombopag, a thrombopoietin receptor agonist, enhances human umbilical cord blood hematopoietic stem/primitive progenitor cell expansion and promotes multi-lineage hematopoiesis.  

PubMed

Umbilical cord blood (UCB) transplantation has emerged as a promising therapy, but it is challenged by scarcity of stem cells. Eltrombopag is a non-peptide, thrombopoietin (TPO) receptor agonist, which selectively activates c-Mpl in humans and chimpanzees. We investigated eltrombopag's effects on human UCB hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) expansion, and its effects on hematopoiesis in vivo. Eltrombopag selectively augmented the expansion of human CD45+, CD34+, and CD41+ cells in bone marrow compartment without effects on mouse bone marrow cells in the NOD/SCID mice xenotransplant model. Consequently, eltrombopag increased peripheral human platelets and white blood cells. We further examined effects in the STAT and AKT signaling pathways in serum-free cultures. Eltrombopag expanded human CD34+ CD38-, CD34+, and CD41+ cells. Both eltrombopag and recombinant human TPO (rhTPO) induced phosphorylation of STAT5 of CD34+ CD41-, CD34- CD41+, and CD34- CD41- cells. rhTPO preferentially induced pSTAT3, pAKT, and more pSTAT5 in CD34- C41+ cells, while eltrombopag had no effects on pSTAT3. In conclusion, eltrombopag enhanced expansion of HSCs/HPCs of human UCB in vivo and in vitro, and promoted multi-lineage hematopoiesis through the expansion of bone marrow HSCs/HPCs of human UCB in vivo. Eltrombopag differed somewhat from rhTPO in the signal transduction pathways by favoring earlier HSC/HPC populations. PMID:22683680

Sun, Hongliang; Tsai, Ying; Nowak, Irena; Liesveld, Jane; Chen, Yuhchyau

2012-09-01

232

Involvement of Cytoskeleton-associated Proteins in the Commitment of C3H10T1/2 Pluripotent Stem Cells to Adipocyte Lineage Induced by BMP2/4*  

PubMed Central

The developmental pathway that gives rise to mature adipocytes involves two distinct stages: commitment and terminal differentiation. Although the important proteins/factors contributing to terminal adipocyte differentiation have been well defined, the proteins/factors in the commitment of mesenchymal stem cells to the adipocyte lineage cells have not. In this study, we applied proteomics analysis profiling to characterize differences between uncommitted C3H10T1/2 pluripotent stem cells and those that have been committed to the adipocyte lineage by BMP4 or BMP2 with the goal to identify such proteins/factors and to understand the molecular mechanisms that govern the earliest stages of adipocyte lineage commitment. Eight proteins were found to be up-regulated by BMP2, and 27 proteins were up-regulated by BMP4, whereas five unique proteins were up-regulated at least 10-fold by both BMP2/4, including three cytoskeleton-associated proteins (i.e. lysyl oxidase (LOX), translationally controlled tumor protein 1 (TPT1), and ?B-crystallin). Western blotting further confirmed the induction of the expression of these cytoskeleton-associated proteins in the committed C3H10T1/2 induced by BMP2/4. Importantly, knockdown of LOX expression totally prevented the commitment, whereas knockdown of TPT1 and ?B-crystallin expression partially inhibited the commitment. Several published reports suggest that cell shape can influence the differentiation of partially committed precursors of adipocytes, osteoblasts, and chondrocytes. We observed a dramatic change of cell shape during the commitment process, and we showed that knockdown of these cytoskeleton-associated proteins prevented the cell shape change and restored F-actin organization into stress fibers and inhibited the commitment to the adipocyte lineage. Our studies indicate that these differentially expressed cytoskeleton-associate proteins might determine the fate of mesenchymal stem cells to commit to the adipocyte lineage through cell shape regulation. PMID:20713452

Huang, Hai-Yan; Hu, Ling-Ling; Song, Tan-Jing; Li, Xi; He, Qun; Sun, Xia; Li, Yi-Ming; Lu, Hao-Jie; Yang, Peng-Yuan; Tang, Qi-Qun

2011-01-01

233

Nicotinamide phosphoribosyltransferase (Nampt) affects the lineage fate determination of mesenchymal stem cells: a possible cause for reduced osteogenesis and increased adipogenesis in older individuals.  

PubMed

Human aging is associated with a progressive decline in bone mass and an accumulation of marrow fat. We found that osteoblast differentiation was reduced and adipocyte formation increased in bone marrow stromal cells derived from aged mice compared with young controls. The increased adipogenesis correlated with a relatively lower Sirt1 activity and a lower intracellular NAD(+) concentration. We suppose that these effects were caused by age-related reduction of nicotinamide phosphoribosyltransferase (Nampt), the enzyme catalyzing NAD resynthesis from nicotinamide (NAM). In support of this hypothesis, treatment with Nampt inhibitor FK866 increased adipocyte formation and reduced mineralization in primary cultured bone marrow stromal cells. In addition, knockdown of Nampt in the mouse mesenchymal cell line C3H10T1/2?cells resulted in decreased Sirt1 activity and enhanced adipogenesis. Interestingly, although Nampt deficiency resulted in both decreased intracellular NAD(+) and increased NAM, the cell differentiation could be controlled only by regulation of NAM. These results indicate that the lineage fate determination of mesenchymal stem cells (MSCs) is influenced by cell energy metabolism and points to a possible mechanism for the development of senile osteoporosis. Furthermore, we suggest that side effects on bone should be considered when evaluating the long-term safety of NAD-interfering pharmaceuticals. PMID:21812028

Li, Yan; He, Xu; Li, Yulin; He, Jiaxue; Anderstam, Björn; Andersson, Göran; Lindgren, Urban

2011-11-01

234

The Story of Dinosaur Evolution  

NSDL National Science Digital Library

In this case study, students write their own “evolution stories” based on information taken from a review article by Paul Sereno on the evolution of dinosaurs published in Science magazine. In the process, they learn to distinguish between the three major groups of dinosaurs based on physical characteristics; trace the ancestry of individual dinosaur species; and interpret a complex evolutionary tree that includes extinctions, speciation events, and changes in the number of taxa over time. The case was designed for use in non-majors introductory science courses, but could also be used in majors’ courses.

Coker, Jeffrey S.; Agnew, Jimmie D.

2005-01-01

235

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.

236

Nanotopography directs mesenchymal stem cells to osteoblast lineage through regulation of microRNA-SMAD-BMP-2 circuit.  

PubMed

The aim of this study was to investigate if chemically produced nanotopography on titanium (Ti) surface induces osteoblast differentiation of cultured human bone marrow mesenchymal stem cells (hMSCs) by regulating the expression of microRNAs (miRs). It was demonstrated that Ti with nanotopography induces osteoblast differentiation of hMSCs as evidenced by upregulation of osteoblast specific markers compared with untreated (control) Ti at day 4. At this time-point, miR-sequencing analysis revealed that 20 miRs were upregulated (>twofold) while 20 miRs were downregulated (>threefold) in hMSCs grown on Ti with nanotopography compared with control Ti. Three miRs, namely miR-4448, -4708, and -4773, which were significantly downregulated (>fivefold) by Ti with nanotopography affect osteoblast differentiation of hMSCs. These miRs directly target SMAD1 and SMAD4, both key transducers of the bone morphogenetic protein 2 (BMP-2) osteogenic signal, which were upregulated by Ti with nanotopography. Overexpression of miR-4448, -4708, and 4773 in MC3T3-E1 pre-osteoblasts noticeably inhibited gene and protein expression of SMAD1 and SMAD4 and therefore repressed the gene expression of key bone markers. Additionally, it was observed that the treatment with BMP-2 displayed a higher osteogenic effect on MC3T3-E1 cells grown on Ti with nanotopography compared with control Ti, suggesting that the BMP-2 signaling pathway was more effective on this surface. Taken together, these results indicate that a complex regulatory network involving a miR-SMAD-BMP-2 circuit governs the osteoblast differentiation induced by Ti with nanotopography. J. Cell. Physiol. 229: 1690-1696, 2014. © 2014 Wiley Periodicals, Inc. PMID:24619927

Kato, Rogerio B; Roy, Bhaskar; De Oliveira, Fabiola S; Ferraz, Emanuela P; De Oliveira, Paulo T; Kemper, Austin G; Hassan, Mohammad Q; Rosa, Adalberto L; Beloti, Marcio M

2014-11-01

237

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

238

How Big Were the Dinosaurs?  

NSDL National Science Digital Library

In this classroom activity, younger students compare their feet to the footprint of a large Apatosaur. The activity opens with background information about the enormous size range of dinosaurs and a discussion in which the students name some of the dinosaurs they know and describe how big they were. Then, each student will make an outline of their own footprint and fasten it onto the full-size Apatosaur print (which must be enlarged from the smaller drawing that is provided).

239

Dinosaurs: Ancient Fossils, New Discoveries  

NSDL National Science Digital Library

This Web site, created to complement the Museum's Dinosaurs: Ancient Fossils, New Discoveries exhibit, offers a virtual visit to the Museum, complete with text, photos, video clips, audio interviews, and more and includes much of the information which was in the original exhibit which is now closed. The site includes information on the bio-mechanics of dinosaurs and the reasons behind some of their strange appearances.

240

Dinosaurs and the island rule: The dwarfed dinosaurs from Haeg Island Michael J. Benton a,  

E-print Network

Dinosaurs and the island rule: The dwarfed dinosaurs from Haeg Island Michael J. Benton a, , Zoltan 2009 Accepted 21 January 2010 Available online 28 January 2010 Keywords: Dinosaurs Cretaceous, in 1914, to suggest that the latest Cretaceous dinosaurs from Haeg, Romania were an island fauna, based

Benton, Michael

241

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 structures of modern birds. UAlberta researcher Phil Currie helped identify the first dinosaur specimens

Machel, Hans

242

Counting dinosaurs: how many kinds were there?  

PubMed

Dinosaurs figure prominently in discussions of mass extinctions and evolutionary metrics, but their usefulness is hampered by archaic taxonomy, imprecise biostratigraphy, and imperfect preservation that bias our understanding of dinosaur diversity. A critical evaluation shows that of 540 genera and 800 species of dinosaurs proposed since 1824, 285 genera and 336 species are probably valid. Nearly half of all genera are based on a single specimen, and complete skulls and skeletons are known for only 20% of all dinosaurs. Dinosaurs are known from every continent. Countries with the greatest known diversity of dinosaurs are (in descending order) the United States, Mongolia, China, Canada, England, and Argentina; the greatest future increases may be expected from Argentina and China. Nearly half of all dinosaur genera are of latest Cretaceous age (Campanian or Maastrichtian). Estimates of the average duration of a dinosaur genus range from 5 million to 10.5 million years, with the most likely value about 7.7 million years. Dinosaurs evolved as rapidly as Cenozoic mammals. Global dinosaur diversity during the Campanian and Maastrichtian is estimated at 100 genera per stage, using a logistic model to estimate future discoveries. A model of increasing diversity and a bottleneck model compensate for the biasis in the preserved fossil record. The number of dinosaurs that have ever lived is estimated at 900-1200 genera. The fossil record of dinosaurs is presently about 25% complete. Dinosaurs disappeared in the Maastrichtian near the peak of their historic diversity. PMID:2217192

Dodson, P

1990-10-01

243

The extinction of the dinosaurs.  

PubMed

Non-avian dinosaurs went extinct 66?million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large-bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult. PMID:25065505

Brusatte, Stephen L; Butler, Richard J; Barrett, Paul M; Carrano, Matthew T; Evans, David C; Lloyd, Graeme T; Mannion, Philip D; Norell, Mark A; Peppe, Daniel J; Upchurch, Paul; Williamson, Thomas E

2014-07-28

244

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

245

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

246

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.

247

Dinosaur Names: Common and Science Names  

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 brainstorm dinosaur names and discover that names are often based on body parts (i.e. rhino means nose). Learners also create drawings of dinosaurs and their body parts in their Dino Diary. This activity is featured on page 10 of the "Dinosphere" unit of study for K-2 learners.

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

2004-01-01

248

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

249

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.

250

Dinosaurs and the Cretaceous Terrestrial Revolution  

E-print Network

Dinosaurs and the Cretaceous Terrestrial Revolution Graeme T. Lloyd1,*, Katie E. Davis2 , Davide of dinosaurs reached its highest peak during the mid- and Late Cretaceous, the 50 Myr that preceded their extinction, and yet this explosion of dinosaur diversity may be explained largely by sampling bias. It has

Benton, Michael

251

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

252

Dinosaur Body Temperatures Determined from Isotopic (13  

E-print Network

Dinosaur Body Temperatures Determined from Isotopic (13 C-18 O) Ordering in Fossil Biominerals of the nonavian dinosaurs is the subject of debate. Previously, arguments have been made for both endothermic° to 7°C lower than predicted by a model that showed scaling of dinosaur body temperature with mass

Schöne, Bernd R.

253

The Evolutionary History of Sauropod Dinosaurs  

Microsoft Academic Search

Most recent studies of dinosaur phylogeny have concentrated on theropods and ornithischians. As a result, the evolutionary relationships of sauropod dinosaurs are poorly understood. In this paper previous studies of sauropod phylogeny are reviewed and contrasted with the results of a recent cladistic analysis. This analysis forms the basis for a reconstruction of sauropod phylogeny. Sauropods diverged from other dinosaurs

Paul Upchurch

1995-01-01

254

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

255

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.

256

The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs.  

PubMed

Taphonomic biases dictate how organisms are represented in the fossil record, but their effect on studies of vertebrate diversity dynamics is poorly studied. In contrast to the high diversity and abundance of small-bodied animals in extant ecosystems, small-bodied dinosaurs are less common than their large-bodied counterparts, but it is unclear whether this reflects unique properties of dinosaurian ecosystems or relates to taphonomic biases. A new, fully domed pachycephalosaurid dinosaur, Acrotholus audeti, from the Santonian of Alberta predates incompletely domed taxa, and provides important new information on pachycephalosaur evolution and the completeness of the ornithischian fossil record. Here we provide the first empirical evidence that the diversity of small-bodied ornithischian dinosaurs is strongly underestimated based on ghost lineages and the high proportion of robust and diagnostic frontoparietal domes compared with other pachycephalosaur fossils. This suggests preservational biases have a confounding role in attempts to decipher vertebrate palaeoecology and diversity dynamics through the Mesozoic. PMID:23652016

Evans, David C; Schott, Ryan K; Larson, Derek W; Brown, Caleb M; Ryan, Michael J

2013-01-01

257

IMPACT #321 ARCHAEORAPTOR: FEATHERED DINOSAUR  

E-print Network

National Geographic Society is widely known as one of the most important promoters of the theory of organic evolution in the eyes of the public. Louis and Richard Leakey might have remained obscure paleoanthropologists except that their research on fossil evidence for human evolution was generously funded and heavily publicized by the National Geographic Society. Now the idea that birds are simply feathered theropod dinosaurs is the prominent evolutionary doctrine being promoted by the society. Recent scientific research funded by National Geographic concerns what have been called “feathered dinosaurs ” from lower Cretaceous strata of the Liaoning province in China. This new research program appears to be directed specifically at changing what the world believes about dinosaurs and their relationship to birds. A recent episode concerns the discovery and promotion of a particular Chinese fossil appearing to be a combination of bird and theropod dinosaur. Is it actually evolution’s missing link between dinosaurs and birds? The episode concerning the fossil provides an extraordinary peek into the peculiar ideology and journalistic slant of a cadre of zealous scientists and the National Geographic Society that promotes them.

From National; Geographic Doesn’t Fly; Steven A. Austin, Ph.D.

2000-01-01

258

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

259

Feeding height stratification among the herbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada  

PubMed Central

Background Herbivore coexistence on the Late Cretaceous island continent of Laramidia has been a topic of great interest, stemming from the paradoxically high diversity and biomass of these animals in relation to the relatively small landmass available to them. Various hypotheses have been advanced to account for these facts, of which niche partitioning is among the most frequently invoked. However, despite its wide acceptance, this hypothesis has not been rigorously tested. This study uses the fossil assemblage from the Dinosaur Park Formation of Alberta as a model to investigate whether niche partitioning facilitated herbivorous dinosaur coexistence on Laramidia. Specifically, the question of feeding height stratification is examined in light of the role it plays in facilitating modern ungulate coexistence. Results Most herbivorous dinosaur species from the Dinosaur Park Formation were restricted to feeding no higher than approximately 1 m above the ground. There is minimal evidence for feeding height partitioning at this level, with ceratopsids capable of feeding slightly higher than ankylosaurs, but the ecological significance of this is ambiguous. Hadrosaurids were uniquely capable of feeding up to 2 m quadrupedally, or up to 5 m bipedally. There is no evidence for either feeding height stratification within any of these clades, or for change in these ecological relationships through the approximately 1.5 Ma record of the Dinosaur Park Formation. Conclusions Although we cannot reject the possibility, we find no good evidence that feeding height stratification, as revealed by reconstructed maximum feeding heights, played an important role in facilitating niche partitioning among the herbivorous dinosaurs of Laramidia. Most browsing pressure was concentrated in the herb layer, although hadrosaurids were capable of reaching shrubs and low-growing trees that were out of reach from ceratopsids, ankylosaurs, and other small herbivores, effectively dividing the herbivores in terms of relative abundance. Sympatric hadrosaurids may have avoided competing with one another by feeding differentially using bipedal and quadrupedal postures. These ecological relationships evidently proved to be evolutionarily stable because they characterize the herbivore assemblage of the Dinosaur Park Formation through time. If niche partitioning served to facilitate the rich diversity of these animals, it may have been achieved by other means in addition to feeding height stratification. Consideration of other feeding height proxies, including dental microwear and skull morphology, may help to alleviate problems of underdetermination identified here. PMID:23557203

2013-01-01

260

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

261

Explorationists and dinosaurs  

SciTech Connect

The exploration industry is changing, exploration technology is changing and the explorationist's job is changing. Resource companies are diversifying internationally and their central organizations are providing advisors rather than services. As a result, the relationship between the resource company and the contractor is changing. Resource companies are promoting standards so that all contract services in all parts of the world will look the same to their advisors. Contractors, for competitive reasons, want to look [open quotes]different[close quotes] from other contractors. The resource companies must encourage competition between contractors to insure the availability of new technology but must also resist the current trend of burdening the contractor with more and more of the risk involved in exploration. It is becoming more and more obvious that geophysical expenditures represent the best [open quotes]value added[close quotes] expenditures in exploration and development budgets. As a result, seismic-related contractors represent the growth component of our industry. The predominant growth is in 3-D seismic technology, and this growth is being further propelled by the computational power of the new generation of massively parallel computers and by recent advances in computer graphic techniques. Interpretation of seismic data involves the analysis of wavelet shapes and amplitudes prior to stacking the data. Thus, modern interpretation involves understanding compressional waves, shear waves, and propagating modes which create noise and interference. Modern interpretation and processing are carried out simultaneously, iteratively, and interactively and involve many physics-related concepts. These concepts are not merely tools for the interpretation, they are the interpretation. Explorationists who do not recognize this fact are going the way of the dinosaurs.

French, W.S. (Grant Tensor Geophysical Corp., Houston, TX (United States))

1993-02-01

262

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.

263

Binocular vision in theropod dinosaurs  

Microsoft Academic Search

The binocular fields of view of seven theropod dinosaurs are mapped using sculpted life reconstructions of their heads and techniques adopted from ophthalmic field perimetry. The tall, narrow snout and laterally facing eyes of the allosauroids Allosaurus and Carcharodontosaurus restricted binocular vision to a region only approximately 20° wide, comparable to that of modern crocodiles. In contrast, the coelurosaurs Daspletosaurus,

Kent A. Stevens

2006-01-01

264

The earliest known sauropod dinosaur  

Microsoft Academic Search

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

Eric Buffetaut; Varavudh Suteethorn; Gilles Cuny; Haiyan Tong; Jean Le Loeuff; Sasidhorn Khansubha; Sutee Jongautchariyakul

2000-01-01

265

The Evolution and Extinction of the Dinosaurs  

NASA Astrophysics Data System (ADS)

Written for non-specialists, this detailed survey of dinosaur origins, diversity, and extinction is designed as a series of successive essays covering important and timely topics in dinosaur paleobiology, such as "warm-bloodedness," birds as living dinosaurs, the new, non-flying feathered dinosaurs, dinosaur functional morphology, and cladistic methods in systematics. Its explicitly phylogenetic approach to the group is that taken by dinosaur specialists. The book is not an edited compilation of the works of many individuals, but a unique, cohesive perspective on Dinosauria. Lavishly illustrated with hundreds of new, specially commissioned illustrations by John Sibbick, world-famous illustrator of dinosaurs, the volume includes multi-page drawings as well as sketches and diagrams. First edition Hb (1996): 0-521-44496-9 David E. Fastovsky is Professor of Geosciences at the University of Rhode Island. Fastovsky, the author of numerous scientific publications dealing with Mesozoic vertebrate faunas and their ancient environments, is also scientific co-Editor of Geology. He has undertaken extensive fieldwork studying dinosaurs and their environments in Montana, North Dakota, Arizona, Mexico, and Mongolia. David B. Weishampel is a professor at the Center for Functional Anatomy and Evolution at Johns Hopkins University, School of Medicine. Weishampel is best known for discovering, researching, and naming several rare European dinosaur species. During the 1980s Weishampel gained fame for his work with American paleontologist Jack Horner and later named the famous plant-eating, egg-laying Orodromeus, Horner. Now, a decade after his pioneering studies with Horner, Weishampel is most widely known for his current work on the Romanian dinosaur fauna. He is the author and co-author of many titles, including The Dinosaur Papers, 1676-1906 (Norton, 2003); The Dinosauria, (University of California, 1990); and Dinosaurs of the East Coast, (Johns Hopkins University Press, 1996).

Fastovsky, David E.; Weishampel, David B.

2005-02-01

266

Network representation of a child's dinosaur knowledge  

Microsoft Academic Search

A 4-yr-old male's knowledge of 40 dinosaurs was elicited from 2 tasks. The data gathered from these knowledge-production protocols were used to map 2 interrelated semantic networks of dinosaurs, viewed as concept nodes connected by links. The 2 mappings corresponded to 2 sets of dinosaurs (20 each), partitioned on the basis of external criteria: mother's subjective judgment of the S's

Michelene T. Chi; Randi D. Koeske

1983-01-01

267

Gideon Mantell and the Discovery of Dinosaurs  

Microsoft Academic Search

Gideon Mantell and the Discovery of Dinosaurs is a scholarly yet accessible biography--the first in a generation--of a pioneering dinosaur hunter and scholar. Gideon Mantell discovered the Iguanodon (a famous tale set right in this book) and several other dinosaur species, spent over twenty-five years restoring Iguanodon fossils, and helped establish the idea of an Age of Reptiles that ended

Dennis R. Dean

1999-01-01

268

Geology Fieldnotes: Dinosaur National Monument, Colorado / Utah  

NSDL National Science Digital Library

Dinosaur National Monument preserves a fossil bone deposit containing the bones of hundreds of dinosaurs, which was once enclosed in the sands of an ancient river. Features of the site include park geology information, maps, photographs, related links, visitor information, multimedia resources, and resources for teaching geology with National Park examples. The geology section discusses the park's geologic history and fossil beds. A park map of the Monument is included, and the photo album section contains drawings of some of the dinosaur species found at the Monument's Dinosaur Quarry.

269

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

270

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

271

[Oligodendrocyte lineage].  

PubMed

The mechanisms leading to cell diversification in the Vertebrate central nervous system are still poorly understood. We have analyzed neural differentiation potentialities of the embryonic chick optic nerve. In the adult, the optic nerve is made up of astrocytes and oligodendrocytes ensheathing retinal axons, but it is entirely devoid of neuronal cell bodies. Using explant cultures and specific cell type markers, we demonstrate that in fact the embryonic optic nerve contains cells endowed with neuronal potentialities but is initially devoid of a potential for oligodendrogenesis. Studies by other groups in rodents suggest that oligodendrocyte precursors may be initially restricted to the ventral region of the developing spinal cord. Taken together, these results indicate that early in development, oligodendrocyte precursors are not distributed homogeneously in the neuroepithelium. Preliminary results in our laboratory show that the specification of the oligodendrocyte lineage in the chick spinal cord may depend on ventral signals from the notochord. PMID:8590224

Cochard, P; Giess, M C

1995-01-01

272

Dinosaurs and the Connecticut Valley  

E-print Network

Fossils of dinosaur tracks have provided scientists with useful information for understanding the geological and paleontological history of the Connecticut Valley. Tracks are well preserved while skeletal remains have been lost due to the geological and climatic features. The brownstone red-beds that dominate the composition of the Connecticut Valley exist in adverse conditions, causing rapid decomposition of organic remains such as bones. Decomposition is aided by abrasion or bacterial and scavenger activity. The study of the tracks has lead to the identification of five different genera of dinosaurs in the Connecticut Valley: anchisaurus, yaleosaurus, coelophysis, ammosaurus, and one identified as a relative of dilophosaurus. Study of the geological features of the Connecticut Valley reveals its initial formation, the environment in which the dinosaurs existed, and the valley's development up to the present day. Roughly 250 million years ago all the continents existed as a single mass known as Pangea. About 50 million years later, Pangea began to break up. This led to the formation of the Eastern Border Fault, and along it, the Newark Terrane. Faults formed in Connecticut, resulting in magma rising to the surface and lava flow. The valley eroded over millions of years leaving steep cliffs of basalts

Katherine Mortensen; Daniel Scollan

273

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

274

Stem cell plasticity  

Microsoft Academic Search

The central dogma in stem cell biology has been that cells isolated from a particular tissue can renew and differentiate into lineages of the tissue it resides in. Several studies have challenged this idea by demonstrating that tissue specific cell have considerable plasticity and can cross-lineage restriction boundary and give rise to cell types of other lineages. However, the lack

Uma Lakshmipathy; Catherine Verfaillie

2005-01-01

275

Adaptive radiation of multituberculate mammals before the extinction of dinosaurs.  

PubMed

The Cretaceous-Paleogene mass extinction approximately 66 million years ago is conventionally thought to have been a turning point in mammalian evolution. Prior to that event and for the first two-thirds of their evolutionary history, mammals were mostly confined to roles as generalized, small-bodied, nocturnal insectivores, presumably under selection pressures from dinosaurs. Release from these pressures, by extinction of non-avian dinosaurs at the Cretaceous-Paleogene boundary, triggered ecological diversification of mammals. Although recent individual fossil discoveries have shown that some mammalian lineages diversified ecologically during the Mesozoic era, comprehensive ecological analyses of mammalian groups crossing the Cretaceous-Paleogene boundary are lacking. Such analyses are needed because diversification analyses of living taxa allow only indirect inferences of past ecosystems. Here we show that in arguably the most evolutionarily successful clade of Mesozoic mammals, the Multituberculata, an adaptive radiation began at least 20 million years before the extinction of non-avian dinosaurs and continued across the Cretaceous-Paleogene boundary. Disparity in dental complexity, which relates to the range of diets, rose sharply in step with generic richness and disparity in body size. Moreover, maximum dental complexity and body size demonstrate an adaptive shift towards increased herbivory. This dietary expansion tracked the ecological rise of angiosperms and suggests that the resources that were available to multituberculates were relatively unaffected by the Cretaceous-Paleogene mass extinction. Taken together, our results indicate that mammals were able to take advantage of new ecological opportunities in the Mesozoic and that at least some of these opportunities persisted through the Cretaceous-Paleogene mass extinction. Similar broad-scale ecomorphological inventories of other radiations may help to constrain the possible causes of mass extinctions. PMID:22419156

Wilson, Gregory P; Evans, Alistair R; Corfe, Ian J; Smits, Peter D; Fortelius, Mikael; Jernvall, Jukka

2012-03-22

276

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

E-print Network

Q: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 of a turkey. Did you know?Did you know? What does China have to do with dinosaurs? Some of the most well

277

theropod dinosaurs. The absence of respiratory turbinates in  

E-print Network

theropod dinosaurs. The absence of respiratory turbinates in theropod dinosaurs indicates of dinosaurs to have achieved ac- tive rates of O2-CO2 exchange that might have approached, or even overlapped in theropods indicates that, although these dinosaurs maintained ectotherm-like routine metabolic rates

278

Dinosaur Locomotion John R Hutchinson, Stanford University, California, USA  

E-print Network

Dinosaur Locomotion John R Hutchinson, Stanford University, California, USA Many lines of evidence must be used to understand dinosaur locomotion: how extinct dinosaurs moved. Introduction: What Evidence and Methods are Useful for Studying Dinosaur Locomotion? Several lines of inquiry offer clues

Hutchinson, John

279

Children's Tacit and Explicit Understandings of Dinosaurs.  

ERIC Educational Resources Information Center

The purpose of this cross-age study was to investigate elementary students' (N=120) tacit and explicit understandings of dinosaurs. Detailed analysis of audiotaped interviews of children's performance during a Piagetian-type clinical interview suggests that children's conceptual understandings of dinosaurs are first developed at a tacit level from…

Barba, Robertta H.

280

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

281

Body Size Distribution of the Dinosaurs  

PubMed Central

The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size. PMID:23284818

O’Gorman, Eoin J.; Hone, David W. E.

2012-01-01

282

Osteology of Dinosaurs at The Field Museum  

NSDL National Science Digital Library

This activity explores vertebrate paleontology/paleobiology of the Mesozoic. It focuses on dinosaur osteology using skeletons and models at The Field Museum in Chicago. Students will compare the morphology of several types of bones between a variety of ornithischian and saurischian dinosaurs.

Plotnick, Roy

283

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 Glen Rose, Cretácico Inferior), Dinosaur Valley State Park, Condado de Somervell, Tejas J. O. Farlow1 Formation; Lower Cretaceous) of the Paluxy River, in what is now Dinosaur Valley State Park (Glen Rose

Falkingham, Peter

284

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.

285

Inferring the Possible Speeds of Dinosaurs?  

NSDL National Science Digital Library

Several lines of evidence are presented in this text that can help us estimate how dinosaurs could move. A good sequence of preserved footprints (called a trackway) can be extrapolated to give a rough estimate of how fast a particular animal was traveling at that moment. The morphology (shape and structure, or anatomy) of dinosaurs may be a more useful tool, but it is much more difficult to use properly. We can compare dinosaurs with extant (living) animals whose motion we understand better, and make assumptions based on the similarities and differences between the two. This is called the morphological paradigm. We can use the laws of physics and apply them to our dinosaurs. This is called biomechanics. Specific dinosaurs are used as examples and active links lead to more information on each.

John Hutchinson

286

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

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; DiGiusto, David L

2014-08-01

287

76 FR 7232 - Notice of Inventory Completion: U.S. Department of the Interior, National Park Service, Dinosaur...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Dinosaur National Monument, Dinosaur, CO AGENCY: National Park Service, Interior...Dinosaur National Monument, Dinosaur, CO, has completed an inventory of human remains...Monument, 4545 Highway 40, Dinosaur, CO 81610, telephone (970) 374-3001....

2011-02-09

288

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

289

N-Q Dinosaur Bones  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Quincy is a tour guide at a museum of science and history. During a tour of the museum, he tells some visitors about a fossilized dinosaur bone that is...

290

The Evolution of Dinosaurs: Much Conjecture, Little Evidence  

E-print Network

The evidence for dinosaur evolution was reviewed, along with the various theories of dinosaur evolution and the evidence for their support. Dinosaurs are commonly believed to have evolved from a small, crocodile-like animal; however, a review of the known fossils provides no evidence for dinosaur evolution from non-dinosaurs, despite the excellent and abundant dinosaur fossil record. This finding is very significant because the bones of many of the average- to larger-sized dinosaurs discovered to date are usually fairly well preserved due to their large size and thickness. Dinosaurs appear abruptly in the fossil record and disappear just as suddenly. The fossil findings for several major dinosaur species also were reviewed.

Jerry Bergman

291

An evolutionary cascade model for sauropod dinosaur gigantism--overview, update and tests.  

PubMed

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

292

Two Feathered Dinosaurs From Northeastern China  

NSDL National Science Digital Library

The Nature Web Special (discussed in the April 29, 1998 Scout Report for Science & Engineering), concerns the discovery by Canadian, Chinese, and American researchers of two species of "theropod dinosaur from China -í dinosaurs with feathers." The Nature site includes a press release, commentary by Kevin Padian of the Department of Integrative Biology and the Museum of Paleontology, University of California, Berkeley, and full text of the article: "Two feathered dinosaurs from northeastern China," (Nature 393, 753-761; 1998), by Quang Ji, et al.

Currie, Philip J.; Ji, Qiang.; Norell, Mark.; Shu-An, Ji.

1998-01-01

293

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

294

STEM?!?!  

ERIC Educational Resources Information Center

The author's son has been an engineer since birth. He never asked "why" as a toddler, it was always "how's it work?" So that he wanted a STEM-based home education was no big surprise. In this article, the author considers what kind of curricula would work best for her complex kid.

Merrill, Jen

2012-01-01

295

Genes from the APETALA3 and PISTILLATA Lineages are Expressed in Developing Vascular Bundles of the Tuberous Rhizome, Flowering Stem and Flower Primordia of Eranthis hyemalis  

PubMed Central

In Arabidopsis thaliana expression of the B?class MADS?box genes APETALA3 (AP3) and PISTILLATA (PI) is confined to petals and stamens but in other plant species these genes are also transcribed in non?flower tissues; in Solanum tuberosum they are transcribed specifically in vascular bundles leading to petals and stamens. Transcription analysis of B?class genes in Eranthis hyemalis using reverse transcribed in situ PCR revealed that both AP3 and PI are expressed in developing vascular bundles in the tuberous rhizome, flowering stem and floral primordia. In addition, AP3 and PI transcripts are also found in stems and leaves. These results suggest a more complex role of B?class genes in Eranthis and possible involvement in the development of vascular tissue. PMID:12096822

SKIPPER, MARTIN

2002-01-01

296

Did You Know? New Data on Dinosaurs.  

ERIC Educational Resources Information Center

New information reveals that dinosaurs have a pelvic structure similar to that of animals that walk upright. Science teachers should remember that theories and assumptions are always provisional and tentative. (JN)

Silverberg, Robert

1981-01-01

297

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.

298

Early Evolution of Titanosauiform Sauropod Dinosaurs.  

E-print Network

??Titanosauriformes was a globally-distributed, long-lived clade of dinosaurs that contains both the largest and smallest known sauropods. In an effort to understand the phylogenetic relationships… (more)

D'Emic, Michael Daniel

2011-01-01

299

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.

300

How a Dinosaur Became a Fossil  

NSDL National Science Digital Library

This interactive resource adapted from the Museum of Paleontology at the University of California, Berkeley shows how a dinosaur can be buried under sediment after it dies, become a fossil, and then become exposed and discovered by paleontologists.

2005-12-17

301

Fossils From China Link Birds with Dinosaurs  

NSDL National Science Digital Library

The discovery by Canadian, Chinese, and American researchers of two species of "theropod dinosaur from China -í dinosaurs with feathers" is reported in the July 1998 issue of National Geographic. The National Geographic site contains information about the discovery, including a brief interview with Quang Ji, images (including a QuickTime VR image), and a 55 minute RealPlayer audio press conference held June 23, 1998.

1998-01-01

302

Dinosaurs in the year of Darwin.  

PubMed

This special issue of The Anatomical Record explores the recent advances in the functional morphology and paleobiology of dinosaurs. Although Darwin did not study dinosaurs because paleontology was in its infancy a century and half ago, he considered both paleontology and anatomy as essential subjects for establishing the validity of evolution. The study of dinosaurs constitutes a vigorous subdiscipline within vertebrate paleontology, and anatomists and evolutionary functional morphologists constitute an especially creative subgroup within dinosaur paleontology. The collection of 17 papers presented in this issue encompass cranial anatomy, postcranial anatomy, and paleobiology of dinosaurs and other archosaurs. Soft tissue subjects include studies of brain structure, jaw adductor muscles, and keratinous appendages of the skull. Taxonomically, it includes four papers with a focus on theropods, including Tyrannosaurus, five papers dealing with ceratopsians, three papers on hadrosaurs, and one on ankylosaurs. Modern anatomical techniques such as CT scanning, finite element analysis, and high resolution histology are emphasized. The visual presentation of results of these studies is spectacular. Results include the first-ever life history table of a plant-eating dinosaur; a determination of the head orientation of Tyrannosaurus and its relatives based on interpretation of the semicircular canals. The claws of Velociraptor appear to best adapted for tree climbing, but not for horrific predatory activities. Pachyrhinosaurus evidently used its massive head for head butting. The tail club of the armored dinosaur Euoplocephalus had the structural integrity to be used as a weapon. The pages abound with insights such as these. Dinosaurs once dead for millions of years live again! PMID:19711448

Dodson, Peter

2009-09-01

303

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 (Chapter 11) These animals are not true dinosaurs, but they are the closest relatives to the dinosaurs

Holtz Jr., Thomas R.

304

First Dinosaur Tracks from the Arabian Peninsula  

E-print Network

Background: The evolutionary history of Mesozoic terrestrial vertebrates from the Arabian Peninsula is virtually unknown. Despite vast exposures of rocky outcrops, only a handful of fossils have yet been described from the region. Here we report a multi-taxon dinosaur track assemblage near Madar village, 47 km north of Sana’a, Republic of Yemen. This represents the first dinosaur tracksite from the Arabian Peninsula, and the only multi-taxon dinosaur ichnosite in the Middle East. Methodology/Findings: Measurements were taken directly from trackway impressions, following standard ichnological conventions. The presence of bipedal trackmakers is evidenced by a long series of pes imprints preserving smoothly rounded posterior margins, no evidence of a hallux, bluntly rounded digit tips and digital divarication angles characteristic of ornithopod dinosaurs. Nearby, eleven parallel quadrupedal trackways document a sauropod herd that included large and small individuals traveling together. Based on the morphology of manus impressions along with a narrow-gauged stance, the quadrupedal trackways were made by non-titanosauriform neosauropods. Additional isolated tracks and trackways of sauropod and ornithopod dinosaurs are preserved nearby. Conclusions/Significance: Taken together, these discoveries present the most evocative window to date into the evolutionary history of dinosaurs of the Arabian Peninsula. Given the limited Mesozoic terrestrial record from the region, this discovery is of both temporal and geographic significance, and massive exposures of similarly-aged outcrops nearby offer

Anne S. Schulp; Mohammed Al-wosabi; Nancy J. Stevens

2008-01-01

305

Derivation of mesenchymal stromal cells from pluripotent stem cells through a neural crest lineage using small molecule compounds with defined media.  

PubMed

Neural crest cells (NCCs) are an embryonic migratory cell population with the ability to differentiate into a wide variety of cell types that contribute to the craniofacial skeleton, cornea, peripheral nervous system, and skin pigmentation. This ability suggests the promising role of NCCs as a source for cell-based therapy. Although several methods have been used to induce human NCCs (hNCCs) from human pluripotent stem cells (hPSCs), such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), further modifications are required to improve the robustness, efficacy, and simplicity of these methods. Chemically defined medium (CDM) was used as the basal medium in the induction and maintenance steps. By optimizing the culture conditions, the combination of the GSK3? inhibitor and TGF? inhibitor with a minimum growth factor (insulin) very efficiently induced hNCCs (70-80%) from hPSCs. The induced hNCCs expressed cranial NCC-related genes and stably proliferated in CDM supplemented with EGF and FGF2 up to at least 10 passages without changes being observed in the major gene expression profiles. Differentiation properties were confirmed for peripheral neurons, glia, melanocytes, and corneal endothelial cells. In addition, cells with differentiation characteristics similar to multipotent mesenchymal stromal cells (MSCs) were induced from hNCCs using CDM specific for human MSCs. Our simple and robust induction protocol using small molecule compounds with defined media enabled the generation of hNCCs as an intermediate material producing terminally differentiated cells for cell-based innovative medicine. PMID:25464501

Fukuta, Makoto; Nakai, Yoshinori; Kirino, Kosuke; Nakagawa, Masato; Sekiguchi, Kazuya; Nagata, Sanae; Matsumoto, Yoshihisa; Yamamoto, Takuya; Umeda, Katsutsugu; Heike, Toshio; Okumura, Naoki; Koizumi, Noriko; Sato, Takahiko; Nakahata, Tatsutoshi; Saito, Megumu; Otsuka, Takanobu; Kinoshita, Shigeru; Ueno, Morio; Ikeya, Makoto; Toguchida, Junya

2014-01-01

306

The Rod Photoreceptor Lineage of Teleost Fish  

PubMed Central

The retinas of postembryonic teleost fish continue to grow for the lifetime of the fish. New retinal cells are added continuously at the retinal margin, by stem cells residing at the circumferential germinal zone. Some of these retinal cells differentiate as Müller glia with cell bodies that reside within the inner nuclear layer. These glia retain some stem cell properties in that they carry out asymmetric cell divisions and continuously generate a population of transit-amplifying cells – the rod photoreceptor lineage – that are committed to rod photoreceptor neurogenesis. These rod progenitors progress through a stereotyped sequence of changes in gene expression as they continue to divide and migrate to the outer nuclear layer. Now referred to as rod precursors, they undergo terminal mitoses and then differentiate as rods, which are inserted into the existing array of rod and cone photoreceptors. The rod lineage displays developmental plasticity, as rod precursors can respond to the loss of rods through increased proliferation, resulting in rod replacement. The stem cells of the rod lineage, Müller glia, respond to acute damage of other retinal cell types by increasing their rate of proliferation. In addition, the Müller glia in an acutely damaged retina dedifferentiate and become multipotent, generating new, functional neurons. This review focuses on the cells of the rod lineage and includes discussions of experiments over the last 30 years that led to their identification and characterization, and the discovery of the stem cells residing at the apex of the lineage. The plasticity of cells of the rod lineage, their relationships to cone progenitors, and the applications of this information for developing future treatments for human retinal disorders will also be discussed. PMID:21742053

Stenkamp, Deborah L.

2011-01-01

307

Transient Downregulation of Nanog and Oct4 Induced by DETA/NO Exposure in Mouse Embryonic Stem Cells Leads to Mesodermal/Endodermal Lineage Differentiation  

PubMed Central

The function of pluripotency genes in differentiation is a matter of investigation. We report here that Nanog and Oct4 are reexpressed in two mouse embryonic stem cell (mESC) lines following exposure to the differentiating agent DETA/NO. Both cell lines express a battery of both endoderm and mesoderm markers following induction of differentiation with DETA/NO-based protocols. Confocal analysis of cells undergoing directed differentiation shows that the majority of cells expressing Nanog express also endoderm genes such as Gata4 and FoxA2 (75.4% and 96.2%, resp.). Simultaneously, mRNA of mesodermal markers Flk1 and Mef2c are also regulated by the treatment. Acetylated histone H3 occupancy at the promoter of Nanog is involved in the process of reexpression. Furthermore, Nanog binding to the promoter of Brachyury leads to repression of this gene, thus disrupting mesendoderm transition. PMID:25544848

Mora-Castilla, Sergio; Tejedo, Juan R.; Díaz, Irene; Hitos, Ana B.; Cahuana, Gladys M.; Hmadcha, Abdelkrim; Martín, Franz; Soria, Bernat

2014-01-01

308

Use of transgenic mice to infer the biological properties of small intestinal stem cells and to examine the lineage relationships of their descendants.  

PubMed

Transgenes, composed of elements of the 5' nontranscribed region of the liver fatty acid-binding protein (L-FABP) gene linked to various reporters, have previously been used to explore the cellular, regional, and temporal differentiation of the mouse intestinal epithelium. In this report, we have analyzed a pedigree of L-FABP/human growth hormone (hGH) transgenic mice that display a stable, heritable, mosaic pattern of reporter expression: wholly hGH-positive or hGH-negative populations of differentiating enterocytes arise from hGH-positive or hGH-negative crypts, respectively, and migrate as vertical coherent bands up the villus producing striped (polyclonal) villi. The ability of enteroendocrine cells within a given villus stripe to support hGH expression coincides with the enterocytic reporter phenotype, suggesting that these two terminally differentiated cells arise from a common multipotent stem cell. hGH-negative crypts are nonrandomly distributed around each villus and their frequency increases along the duodenal-to-ileal axis. Statistical analysis of the observed villus striping pattern suggests that transgene expression is not independently determined in individual crypts but rather in multicrypt "patches." The intact endogenous mouse L-FABP gene (Fabpl) exhibits a similar striped villus pattern of expression in a portion of the distal small intestine. These studies indicate that Fabpl and L-FABP/hGH transgenes represent sensitive markers for exploring the biological properties of gut stem cells and how positional information is encoded in this rapidly and continuously renewing epithelium. PMID:1946352

Roth, K A; Hermiston, M L; Gordon, J I

1991-11-01

309

Use of transgenic mice to infer the biological properties of small intestinal stem cells and to examine the lineage relationships of their descendants.  

PubMed Central

Transgenes, composed of elements of the 5' nontranscribed region of the liver fatty acid-binding protein (L-FABP) gene linked to various reporters, have previously been used to explore the cellular, regional, and temporal differentiation of the mouse intestinal epithelium. In this report, we have analyzed a pedigree of L-FABP/human growth hormone (hGH) transgenic mice that display a stable, heritable, mosaic pattern of reporter expression: wholly hGH-positive or hGH-negative populations of differentiating enterocytes arise from hGH-positive or hGH-negative crypts, respectively, and migrate as vertical coherent bands up the villus producing striped (polyclonal) villi. The ability of enteroendocrine cells within a given villus stripe to support hGH expression coincides with the enterocytic reporter phenotype, suggesting that these two terminally differentiated cells arise from a common multipotent stem cell. hGH-negative crypts are nonrandomly distributed around each villus and their frequency increases along the duodenal-to-ileal axis. Statistical analysis of the observed villus striping pattern suggests that transgene expression is not independently determined in individual crypts but rather in multicrypt "patches." The intact endogenous mouse L-FABP gene (Fabpl) exhibits a similar striped villus pattern of expression in a portion of the distal small intestine. These studies indicate that Fabpl and L-FABP/hGH transgenes represent sensitive markers for exploring the biological properties of gut stem cells and how positional information is encoded in this rapidly and continuously renewing epithelium. Images PMID:1946352

Roth, K A; Hermiston, M L; Gordon, J I

1991-01-01

310

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, Garbiñe; Infante, Arantza; Schlangen, Karin; Aransay, Ana M.; Fullaondo, Ane; Soriano, Mario; García-Verdugo, José Manuel; Martín, Ángel G.

2012-01-01

311

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

312

Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds  

E-print Network

LETTERS Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds Fucheng Zhang1 greatly expanded our knowledge of the diversity and palaeobiology of dinosaurs and early birds, and con) feathers and integumentary fila- ments are preserved in birds3­5 and non-avian theropod dinosaurs6

Benton, Michael

313

DWARFING IN ORNITHOPOD DINOSAURS FROM THE EARLY CRETACEOUS OF ROMANIA  

E-print Network

DWARFING IN ORNITHOPOD DINOSAURS FROM THE EARLY CRETACEOUS OF ROMANIA Michael J. BENTON1 , Nicholas maturation in the descendant. Key words. Dinosaur, dwarfing, island faunas, Cretaceous, Romania. Rezumat), but the pterosaur and supposed bird remains still await revision. The dinosaurs aroused interest from the beginning

Benton, Michael

314

GEOL 104 Dinosaurs: A Natural History Anatomy and Taxonomy Assignment  

E-print Network

Name: 1 GEOL 104 Dinosaurs: A Natural History Anatomy and Taxonomy Assignment DUE: Fri. Sept. 29 Part I. Comparative Anatomy Below is the skull of the early primitive meat-eating dinosaur 25) Ulna 26) A Metacarpal 27) A Metatarsal 28) Chevron 29) Acetabulum Extra Credit) This dinosaur

Holtz Jr., Thomas R.

315

Dinosaur Fossils Predict Body Temperatures James F. Gillooly1*  

E-print Network

Dinosaur Fossils Predict Body Temperatures James F. Gillooly1* , Andrew P. Allen2 , Eric L. Charnov of America Perhaps the greatest mystery surrounding dinosaurs concerns whether they were endotherms, ectotherms, or some unique intermediate form. Here we present a model that yields estimates of dinosaur body

Allen, Andrew P.

316

Response to Comment on "Ascent of Dinosaurs Linked to  

E-print Network

Response to Comment on "Ascent of Dinosaurs Linked to an Iridium Anomaly at the Triassic-Jurassic Boundary" Our recent study on the nature of the ascent of the dinosaurs (1) argued three main points: (i dinosaurs appear im- mediately after the boundary (based on foot- prints); and (iii) that both the boundary

Olsen, Paul E.

317

INTEGRATED LIDAR & PHOTOGRAMMETRIC DOCUMENTATION OF THE RED GULCH DINOSAUR  

E-print Network

101 INTEGRATED LIDAR & PHOTOGRAMMETRIC DOCUMENTATION OF THE RED GULCH DINOSAUR TRACKSITE (WYOMING. At the First International Symposium on Dinosaur Tracks and Traces in 1989, concerns were expressed about discovery and formal description in 2001, the Red Gulch Dinosaur Tracksite (RGDT) in northern Wyoming (USA

Falkingham, Peter

318

Estimating the diversity of dinosaurs Steve C. Wang*  

E-print Network

Estimating the diversity of dinosaurs Steve C. Wang* and Peter Dodson *Department of Mathematics, little effort has been devoted to estimating the diversity of dinosaurs. Here we estimate the diversity of nonavian dinosaurs at 1,850 genera, including those that remain to be discovered. With 527 genera currently

Wang, Steve C.

319

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

320

All about Dinosaurs. Animal Life for Children. [Videotape].  

ERIC Educational Resources Information Center

Dinosaurs were the rulers of the land 65 million years ago. In this videotape, children learn more about the different kinds of dinosaurs by viewing vivid illustrations and fossil discoveries. Students compare the dinosaurs to their modern kin--snakes, lizards, and crocodiles. Students also listen to different theories to try to answer the big…

2000

321

C/EBP? Is Required for Long-Term Self-Renewal and Lineage Priming of Hematopoietic Stem Cells and for the Maintenance of Epigenetic Configurations in Multipotent Progenitors  

PubMed Central

Transcription factors are key regulators of hematopoietic stem cells (HSCs) and act through their ability to bind DNA and impact on gene transcription. Their functions are interpreted in the complex landscape of chromatin, but current knowledge on how this is achieved is very limited. C/EBP? is an important transcriptional regulator of hematopoiesis, but its potential functions in HSCs have remained elusive. Here we report that C/EBP? serves to protect adult HSCs from apoptosis and to maintain their quiescent state. Consequently, deletion of Cebpa is associated with loss of self-renewal and HSC exhaustion. By combining gene expression analysis with genome-wide assessment of C/EBP? binding and epigenetic configurations, we show that C/EBP? acts to modulate the epigenetic states of genes belonging to molecular pathways important for HSC function. Moreover, our data suggest that C/EBP? acts as a priming factor at the HSC level where it actively promotes myeloid differentiation and counteracts lymphoid lineage choice. Taken together, our results show that C/EBP? is a key regulator of HSC biology, which influences the epigenetic landscape of HSCs in order to balance different cell fate options. PMID:24415956

Hasemann, Marie S.; Lauridsen, Felicia K. B.; Waage, Johannes; Jakobsen, Janus S.; Frank, Anne-Katrine; Schuster, Mikkel B.; Rapin, Nicolas; Bagger, Frederik O.; Hoppe, Philipp S.; Schroeder, Timm; Porse, Bo T.

2014-01-01

322

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

323

GEOL 104 Dinosaurs: A Natural History Smithsonian Assignment I: Osteology and Life on Land before the Dinosaurs  

E-print Network

Name: 1 GEOL 104 Dinosaurs: A Natural History Smithsonian Assignment I: Osteology and Life on Land before the Dinosaurs DUE: October 9 "Every man is a valuable member of society who by his observations of dinosaur and other fossils in the world. The Smithsonian museums are free; hours for the NMNH are 10 am

Holtz Jr., Thomas R.

324

New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism  

E-print Network

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 (largebodied 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

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

325

Rapid Generation of Functional Dopaminergic Neurons From Human Induced Pluripotent Stem Cells Through a Single-Step Procedure Using Cell Lineage Transcription Factors  

PubMed Central

Current protocols for in vitro differentiation of human induced pluripotent stem cells (hiPSCs) to generate dopamine (DA) neurons are laborious and time-expensive. In order to accelerate the overall process, we have established a fast protocol by expressing the developmental transcription factors ASCL1, NURR1, and LMX1A. With this method, we were able to generate mature and functional dopaminergic neurons in as few as 21 days, skipping all the intermediate steps for inducting and selecting embryoid bodies and rosette-neural precursors. Strikingly, the resulting neuronal conversion process was very proficient, with an overall efficiency that was more than 93% of all the coinfected cells. hiPSC-derived DA neurons expressed all the critical molecular markers of the DA molecular machinery and exhibited sophisticated functional features including spontaneous electrical activity and dopamine release. This one-step protocol holds important implications for in vitro disease modeling and is particularly amenable for exploitation in high-throughput screening protocols. PMID:23658252

Theka, Ilda; Caiazzo, Massimiliano; Dvoretskova, Elena; Leo, Damiana; Ungaro, Federica; Curreli, Sebastiano; Managò, Francesca; Dell'Anno, Maria Teresa; Pezzoli, Gianni; Gainetdinov, Raul R.; Dityatev, Alexander

2013-01-01

326

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

327

The evolution of dinosaur tooth enamel microstructure.  

PubMed

The evolution of tooth enamel microstructure in both extinct and extant mammalian groups has been extensively documented, but is poorly known in reptiles, including dinosaurs. Previous intensive sampling of dinosaur tooth enamel microstructure revealed that: (1) the three-dimensional arrangement of enamel types and features within a tooth-the schmelzmuster-is most useful in diagnosing dinosaur clades at or around the family level; (2) enamel microstructure complexity is correlated with tooth morphology complexity and not necessarily with phylogenetic position; and (3) there is a large amount of homoplasy within Theropoda but much less within Ornithischia. In this study, the examination of the enamel microstructure of 28 additional dinosaur taxa fills in taxonomic gaps of previous studies and reinforces the aforementioned conclusions. Additionally, these new specimens reveal that within clades such as Sauropodomorpha, Neotheropoda, and Euornithopoda, the more basal taxa have simpler enamel that is a precursor to the more complex enamel of more derived taxa and that schmelzmusters evolve in a stepwise fashion. In the particularly well-sampled clade of Euornithopoda, correlations between the evolution of dental and enamel characters could be drawn. The ancestral schmelzmuster for Genasauria remains ambiguous due to the dearth of basal ornithischian teeth available for study. These new specimens provide new insights into the evolution of tooth enamel microstructure in dinosaurs, emphasizing the importance of thorough sampling within broadly inclusive clades, especially among their more basal members. PMID:20518758

Hwang, Sunny H

2011-02-01

328

The complete skull and skeleton of an early dinosaur.  

PubMed

The unearthing of a complete skull and skeleton of the early dinosaur Herrerasaurus ischigualastensis sheds light on the early evolution of dinosaurs. Discovered in the Upper Triassic Ischigualasto Formation of Argentina, the fossils show that Herrerasaurus, a primitive theropod, was an agile, bipedal predator with a short forelimb specialized for grasping and raking. The fossils clarify anatomical features of the common ancestor of all dinosaurs. Herrerasaurus and younger dinosaurs from Upper Triassic beds in Argentina suggest that the dinosaurian radiation was well under way before dinosaurs dominated terrestrial vertebrate communities in taxonomic diversity and abundance. PMID:17789086

Sereno, P C; Novas, F E

1992-11-13

329

What Lies Beneath: Sub-Articular Long Bone Shape Scaling in Eutherian Mammals and Saurischian Dinosaurs Suggests Different Locomotor Adaptations for Gigantism  

PubMed Central

Eutherian mammals and saurischian dinosaurs both evolved lineages of huge terrestrial herbivores. Although significantly more saurischian dinosaurs were giants than eutherians, the long bones of both taxa scale similarly and suggest that locomotion was dynamically similar. However, articular cartilage is thin in eutherian mammals but thick in saurischian dinosaurs, differences that could have contributed to, or limited, how frequently gigantism evolved. Therefore, we tested the hypothesis that sub-articular bone, which supports the articular cartilage, changes shape in different ways between terrestrial mammals and dinosaurs with increasing size. Our sample consisted of giant mammal and reptile taxa (i.e., elephants, rhinos, sauropods) plus erect and non-erect outgroups with thin and thick articular cartilage. Our results show that eutherian mammal sub-articular shape becomes narrow with well-defined surface features as size increases. In contrast, this region in saurischian dinosaurs expands and remains gently convex with increasing size. Similar trends were observed in non-erect outgroup taxa (monotremes, alligators), showing that the trends we report are posture-independent. These differences support our hypothesis that sub-articular shape scales differently between eutherian mammals and saurischian dinosaurs. Our results show that articular cartilage thickness and sub-articular shape are correlated. In mammals, joints become ever more congruent and thinner with increasing size, whereas archosaur joints remained both congruent and thick, especially in sauropods. We suggest that gigantism occurs less frequently in mammals, in part, because joints composed of thin articular cartilage can only become so congruent before stress cannot be effectively alleviated. In contrast, frequent gigantism in saurischian dinosaurs may be explained, in part, by joints with thick articular cartilage that can deform across large areas with increasing load. PMID:24130690

Bonnan, Matthew F.; Wilhite, D. Ray; Masters, Simon L.; Yates, Adam M.; Gardner, Christine K.; Aguiar, Adam

2013-01-01

330

Gideon Mantell and the Discovery of Dinosaurs  

NASA Astrophysics Data System (ADS)

Gideon Mantell and the Discovery of Dinosaurs is a scholarly yet accessible biography--the first in a generation--of a pioneering dinosaur hunter and scholar. Gideon Mantell discovered the Iguanodon (a famous tale set right in this book) and several other dinosaur species, spent over twenty-five years restoring Iguanodon fossils, and helped establish the idea of an Age of Reptiles that ended with their extinction at the conclusion of the Mesozoic Era. He had significant interaction with such well-known figures as James Parkinson, Georges Cuvier, Charles Lyell, Roderick Murchison, Charles Darwin, and Richard Owen. Dennis Dean, a well-known scholar of geology and the Victorian era, here places Mantell's career in its cultural context, employing original research in archives throughout the world, including the previously unexamined Mantell family papers in New Zealand.

Dean, Dennis R.

1999-01-01

331

ELSEVIER Palaeogeography, Palaeoclimatology, Palaeoecology 130(1997) 275-292 Dinosaurs and other tetrapods in an Early Cretaceous bauxite-  

E-print Network

ELSEVIER Palaeogeography, Palaeoclimatology, Palaeoecology 130(1997) 275-292 PAI O Dinosaurs from ornithopod dinosaurs and rarer pterosaurs. Bird specimens reported previously from this fauna for insular adaptations in the dinosaur faunas. The ornithopod dinosaurs may include several taxa

Benton, Michael

332

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.

333

Journal of Zoology Journal of Zoology. Print ISSN 0952-8369 LETTER Allometric equations for predicting body mass of dinosaurs:  

E-print Network

‘In the statistics of today, transformations... [aid] in the analysis of data by bending the data nearer the Procrustean bed of the assumptions underlying conventional analyses’ (Tukey, 1957). This letter is in response to Cawley & Janacek (2010), who take exception with our critique of a widely used procedure for estimating body mass of dinosaurs and other giant animals in extinct lineages (Packard, Boardman & Birchard, 2009). Although the mass of dinosaurs certainly was at issue in our critique, the article actually was a general indictment of the traditional method for estimating parameters in two-parameter allometric equations. Thus, in their challenge to our analysis, Cawley and Janacek essentially mount a defense for the traditional way of doing things (see also their reference to Kerkhoff & Enquist, 2009). This defense is flawed, however,

G. C. Packard; T. J. Boardman; G. F. Birchard

334

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

335

Sequence stratigraphic controls on synsedimentary cementation and preservation of dinosaur tracks: Example from the lower Cretaceous,  

E-print Network

Sequence stratigraphic controls on synsedimentary cementation and preservation of dinosaur tracks in the Upper Albian Dakota Formation of southeastern Nebraska contains the first dinosaur tracks; Diagenesis; Isotopes; Dinosaur tracks; Carbonate cements 1. Introduction The preservation of fossils

González, Luis A.

336

Paleobiology and skeletochronology of Jurassic dinosaurs: implications from the histology and oxygen  

E-print Network

Paleobiology and skeletochronology of Jurassic dinosaurs: implications from the histology Abstract Fossil biogenic phosphate of fast-growing primary bone tissue of dinosaurs can preserve dinosaurs with different histologic patterns of bone growth, high-resolution oxygen isotope profiles were

Schöne, Bernd R.

337

LE BULLETIN DE L'EPI N 54 LES DINOSAURES ET LES MOHICANS TRIBUNE LIBRE  

E-print Network

31 LE BULLETIN DE L'EPI N° 54 LES DINOSAURES ET LES MOHICANS TRIBUNE LIBRE LES DINOSAURES ET LES certains esprits embrumés : pourquoi ne pas regrouper et parquer les derniers dinosaures et les derniers

Paris-Sud XI, Université de

338

Crocodilian behaviour: a window to dinosaur behaviour?  

Microsoft Academic Search

Modern crocodilians and birds are the only living representatives of the Archosauria, a group that also includes non-avian dinosaurs and pterosaurs. Modern crocodilians originated during the early Cretaceous period and dispersed globally. Examples of physiological similarities between living crocodilians and birds include similar amino acids in ?-keratins among crocodiles, turtles and birds; oviduct homologies between crocodilians and birds; similar forelimb

Peter Brazaitis; Myrna E. Watanabe

2011-01-01

339

Dinosaur diversity and the rock record.  

PubMed

Palaeobiodiversity analysis underpins macroevolutionary investigations, allowing identification of mass extinctions and adaptive radiations. However, recent large-scale studies on marine invertebrates indicate that geological factors play a central role in moulding the shape of diversity curves and imply that many features of such curves represent sampling artefacts, rather than genuine evolutionary events. In order to test whether similar biases affect diversity estimates for terrestrial taxa, we compiled genus-richness estimates for three Mesozoic dinosaur clades (Ornithischia, Sauropodomorpha and Theropoda). Linear models of expected genus richness were constructed for each clade, using the number of dinosaur-bearing formations available through time as a proxy for the amount of fossiliferous rock outcrop. Modelled diversity estimates were then compared with observed patterns. Strong statistically robust correlations demonstrate that almost all aspects of ornithischian and theropod diversity curves can be explained by geological megabiases, whereas the sauropodomorph record diverges from modelled predictions and may be a stronger contender for identifying evolutionary signals. In contrast to other recent studies, we identify a marked decline in dinosaur genus richness during the closing stages of the Cretaceous Period, indicating that the clade decreased in diversity for several million years prior to the final extinction of non-avian dinosaurs at the Cretaceous-Palaeocene boundary. PMID:19403535

Barrett, Paul M; McGowan, Alistair J; Page, Victoria

2009-07-22

340

Did dinosaurs come up to scratch?  

Microsoft Academic Search

The high specificity of bird ectoparasites has frequently been interpreted to mean that they have a long evolutionary history. Either they were present as parasites before the main diversification of birds in the Cretaceous period, or they evolved independently into avian parasites on several occasions. The recent discovery of dinosaurs with feathers suggests that birds may have inherited some of

David M. Martill; Paul G. Davis

1998-01-01

341

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

342

Four-winged dinosaurs from China  

Microsoft Academic Search

Although the dinosaurian hypothesis of bird origins is widely accepted, debate remains about how the ancestor of birds first learned to fly. Here we provide new evidence suggesting that basal dromaeosaurid dinosaurs were four-winged animals and probably could glide, representing an intermediate stage towards the active, flapping-flight stage. The new discovery conforms to the predictions of early hypotheses that proavians

Xing Xu; Zhonghe Zhou; Xiaolin Wang; Xuewen Kuang; Fucheng Zhang; Xiangke Du

2003-01-01

343

A Day in the Desert Digging Dinosaurs  

E-print Network

The purpose of a “Virtual Field Trip ” is to present studied concepts and facts in a “realworld” environment. This allows students to practice understanding by applying logic and reasoning in a unique, hopefully memorable, format. A Day in the Desert Digging Dinosaurs describes a college student’s experience in the field

A Virtual; Field Trip; Rebekah K. Nix

344

THE FOSSIL RECORD OF PREDATION IN DINOSAURS  

Microsoft Academic Search

Predatory theropod dinosaurs can usually be identified as such by features of their jaws, teeth, and postcrania, but different clades of these reptiles differed in their adaptations for prey handling. Inferences about theropod diets and hunting behavior based on functional morphology are sometimes supported by evidence from taphonomic associations with likely prey species, bite marks, gut contents, coprolites, and trackways.

JAMES O. FARLOW; THOMAS R. HOLTZ

345

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.

346

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.

347

Atmospheric pressure at the time of dinosaurs  

Microsoft Academic Search

From bioenergetics, fluid mechanics and aerodynamics, we show that if the atmospheric pressure was higher at the time of the dinosaurs than it is today, we would be able to resolve a number of anomalies which puzzle scientists today. These concern how a giant pterosaur (quetzalcoatlus, with a 12-15 m wingspan) had enough power to fly; also, how a giant

Octave Levenspiel

2006-01-01

348

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--the Dinosaurs' Closest Relatives (Chapter 11) These animals are not true dinosaurs, but they are the closest relatives to the dinosaurs that we know of. Name Meaning Age Time Length Weight Where found Comments

Holtz Jr., Thomas R.

349

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--Dinosaurs' Closest Relatives (Chapter 11) These animals are not true dinosaurs, but they are the closest relatives to the dinosaurs that we know of. Name Meaning Age Time Length Weight Where found Comments Lagosuchus rabbit

Holtz Jr., Thomas R.

350

Estimating Speeds of Dinosaurs: a Re-Evaluation of AssumptionsEstimating Speeds of Dinosaurs: a Re-Evaluation of Assumptions 1. INTRODUCTION1. INTRODUCTION  

E-print Network

Estimating Speeds of Dinosaurs: a Re-Evaluation of AssumptionsEstimating Speeds of Dinosaurs: a Re-Evaluation of Assumptions 1. INTRODUCTION1. INTRODUCTION · Paleontologists estimate speeds of dinosaurs from their trackways: ­ McNeill Alexander (1976): hip height is approximately 4x foot length in a variety of dinosaurs, both

Rainforth, Emma C.

351

New hadrosaurid dinosaurs from the uppermost Cretaceous of northeastern China  

E-print Network

Several hundred disarticulated dinosaur bones have been recovered from a large quarry at Wulaga (Heilongjiang Prov? ince, China), in the Upper Cretaceous (Maastrichtian) Yuliangze Formation. The Wulaga quarry can be regarded as a monodominant bonebed: more than 80 % of the bones belong to a new lambeosaurine hadrosaurid, Sahaliyania elunchunorum gen. et sp. nov. This taxon is characterised by long and slender paroccipital processes, a prominent lateral depression on the dorsal surface of the frontal, a quadratojugal notch that is displaced ventrally on the quadrate, and a prepubic blade that is asymmetrically expanded, with an important emphasis to the dorsal side. Phylogenetic analysis shows that Sahaliyania is a derived lambeosaurine that forms a monophyletic group with the corythosaur and para? sauroloph clades. Nevertheless, the exact position of Sahaliyania within this clade cannot be resolved on the basis of the available material. Besides Sahaliyania, other isolated bones display a typical hadrosaurine morphology and are referred to Wulagasaurus dongi gen. et sp. nov., a new taxon characterised by the maxilla pierced by a single foramen below the jugal process, a very slender dentary not pierced by foramina, and by the deltopectoral crest (on the humerus) oriented cranially. Phylogenetic analysis indicates that Wulagasaurus is the most basal hadrosaurine known to date. Phylogeo? graphic data suggests that the hadrosaurines, and thus all hadrosaurids, are of Asian origin, which implies a relatively long ghost lineage of approximately 13 million years for basal hadrosaurines in Asia.

Pascal Godefroit; Hai Shulin; Yu Tingxiang; Pascaline Lauters

352

Sauropod dinosaur embryos from the Late Cretaceous of Patagonia  

Microsoft Academic Search

Definitive non-avian dinosaur embryos, those contained inside fossil eggs, are rare,. Here we describe the first known unequivocal embryonic remains of sauropod dinosaurs-the only known non-avian dinosaur embryos from Gondwana-from a nesting ground in the Upper Cretaceous stage of Patagonia, Argentina. At this new site, Auca Mahuevo (Fig. 1), thousands of eggs are distributed over an area greater than 1km2.

Luis M. Chiappe; Rodolfo A. Coria; Lowell Dingus; Frankie Jackson; Anusuya Chinsamy; Marilyn Fox

1998-01-01

353

The smallest known non-avian theropod dinosaur  

Microsoft Academic Search

Non-avian dinosaurs are mostly medium to large-sized animals, and to date all known mature specimens are larger than the most primitive bird, Archaeopteryx. Here we report on a new dromaeosaurid dinosaur, Microraptor zhaoianus gen. et sp. nov., from the Early Cretaceous Jiufotang Formation of Liaoning, China. This is the first mature non-avian dinosaur to be found that is smaller than

Xing Xu; Zhonghe Zhou; Xiaolin Wang

2000-01-01

354

Dinosaurs: Warm Blooded or Cold Blooded? Gumundur Freyr Matthasson  

E-print Network

Dinosaurs: Warm Blooded or Cold Blooded? Guðmundur Freyr Matthíasson Laufásvegur 42, 101 Reykjavík 09.60.31 Jarðsaga 1. Haust 2003 During the Mesozoic era, dinosaurs reigned supreme on the planet that this was not so, that dinosaurs were, indeed, warm-blooded. Several arguments have been put forth by both camps

Ingólfsson, �lafur

355

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.

356

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

357

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

358

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

359

Cell lineage involvement of recurrent chromosomal abnormalities in hematologic neoplasms.  

PubMed

Analysis of most hematologic neoplasms indicates the involvement of one or more cell lineages in the bone marrow and/or the blood but rules out the involvement of all lineages in any one neoplasm. It is important to detect lineage involvement in order to clarify which stem cells are involved in leukemia, to predict prognosis, and to select appropriate treatment. Our aim was to study the cell lineage involvement of some of the recurrent chromosomal abnormalities seen in hematological neoplasms. The direct morphology-antibody-chromosomes (MAC) method was used. The deletion 20q in myeloproliferative diseases (MPD), the deletion of 5q and t(1;7) in myelodysplastic syndromes (MDS), and t(3;3) in acute myeloid leukemia subtype M7 (AML-M7) were seen in all or at least in two myeloid lineages. These were interpreted as stem cell abnormalities. Deletion 13q in MPD, t(8;21) in AML-M2 and t(15;17) in AML-M3 were seen in granulocytic lineages only; t(14;18) in non-Hodgkin's lymphoma and trisomy 12 as the sole abnormality in chronic lymphocytic leukemia (B-CLL) were seen only in immunoglobulin light chain clonal B cells; inversion 14 in T-CLL was seen only in T cells, whereas t(15;14) in acute lymphocytic leukemia with eosinophilia (ALL-EO) was seen in lymphoid stem cells but not in mature granulocytes or lymphocytes. Additional abnormalities (in addition to the Philadelphia chromosome) in chronic myeloid leukemia (CML) were seen in all myeloid cell lineages and also in mature granulocytes, B cells, and large granular lymphocytes. Abnormalities in Hodgkin's disease were restricted to CD30-positive Reed-Sternberg cells. Trisomy 8 and monosomy 7 are abnormalities that may be present in either stem cells or any of the single cell lineages. PMID:7520272

Knuutila, S; Teerenhovi, L; Larramendy, M L; Elonen, E; Franssila, K O; Nylund, S J; Timonen, T; Heinonen, K; Mahlamäki, E; Winqvist, R

1994-06-01

360

Introgression of mitochondrial DNA among lineages in a hybridogenetic ant.  

PubMed

We report a remarkable pattern of incongruence between nuclear and mitochondrial variations in a social insect, the desert ant Cataglyphis hispanica. This species reproduces by social hybridogenesis. In all populations, two distinct genetic lineages coexist; non-reproductive workers develop from hybrid crosses between the lineages, whereas reproductive offspring (males and new queens) are typically produced asexually by parthenogenesis. Genetic analyses based on nuclear markers revealed that the two lineages remain highly differentiated despite constant hybridization for worker production. Here, we show that, in contrast with nuclear DNA, mitochondrial DNA (mtDNA) does not recover the two lineages as monophyletic. Rather, mitochondrial haplotypes cluster according to their geographical origin. We argue that this cytonuclear incongruence stems from introgression of mtDNA among lineages, and review the mechanisms likely to explain this pattern under social hybridogenesis. PMID:25652221

Darras, Hugo; Aron, Serge

2015-02-01

361

Instruction of hematopoietic lineage choice by cytokine signaling.  

PubMed

Hematopoiesis is the cumulative consequence of finely tuned signaling pathways activated through extrinsic factors, such as local niche signals and systemic hematopoietic cytokines. Whether extrinsic factors actively instruct the lineage choice of hematopoietic stem and progenitor cells or are only selectively allowing survival and proliferation of already intrinsically lineage-committed cells has been debated over decades. Recent results demonstrated that cytokines can instruct lineage choice. However, the precise function of individual cytokine-triggered signaling molecules in inducing cellular events like proliferation, lineage choice, and differentiation remains largely elusive. Signal transduction pathways activated by different cytokine receptors are highly overlapping, but support the production of distinct hematopoietic lineages. Cellular context, signaling dynamics, and the crosstalk of different signaling pathways determine the cellular response of a given extrinsic signal. New tools to manipulate and continuously quantify signaling events at the single cell level are therefore required to thoroughly interrogate how dynamic signaling networks yield a specific cellular response. PMID:25046868

Endele, Max; Etzrodt, Martin; Schroeder, Timm

2014-12-10

362

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

363

Models for the rise of the dinosaurs.  

PubMed

Dinosaurs arose in the early Triassic in the aftermath of the greatest mass extinction ever and became hugely successful in the Mesozoic. Their initial diversification is a classic example of a large-scale macroevolutionary change. Diversifications at such deep-time scales can now be dissected, modelled and tested. New fossils suggest that dinosaurs originated early in the Middle Triassic, during the recovery of life from the devastating Permo-Triassic mass extinction. Improvements in stratigraphic dating and a new suite of morphometric and comparative evolutionary numerical methods now allow a forensic dissection of one of the greatest turnovers in the history of life. Such studies mark a move from the narrative to the analytical in macroevolutionary research, and they allow us to begin to answer the proposal of George Gaylord Simpson, to explore adaptive radiations using numerical methods. PMID:24456985

Benton, Michael J; Forth, Jonathan; Langer, Max C

2014-01-20

364

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.

Constance Soja

365

Hanford: The evolution of a dinosaur  

SciTech Connect

This article describes how the Westinghouse Hanford Company is reinventing the US DOE`s Hanford Site, turning a 1940s-era dinosaur into a 1990s-style business. The major topics covered include the following: breaking the logjam by ending the inefficient cost-plus days; Concentrating resources on resolving urgent safety issues; contract reform with more incentive, greater risk; finally reengineering: the next step.

Fulton, J.

1995-11-01

366

Dinosaur Peptides Suggest Mechanisms of Protein Survival  

PubMed Central

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. PMID:21687667

San Antonio, James D.; Schweitzer, Mary H.; Jensen, Shane T.; Kalluri, Raghu; Buckley, Michael; Orgel, Joseph P. R. O.

2011-01-01

367

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

368

REPORTS Avian Paternal Care Had Dinosaur Origin  

E-print Network

The repeated discovery of adult dinosaurs in close association with egg clutches leads to speculation over the type and extent of care exhibited by these extinct animals for their eggs and young. To assess parental care in Cretaceous troodontid and oviraptorid dinosaurs, we examined clutch volume and the bone histology of brooding adults. In comparison to four archosaur care regressions, the relatively large clutch volumes of Troodon, Oviraptor, and Citipati scale most closely with a bird-paternal care model. Clutch-associated adults lack the maternal and reproductively associated histologic features common to extant archosaurs. Large clutch volumes and a suite of reproductive features shared only with birds favor paternal care, possibly within a polygamous mating system. Paternal care in both troodontids and oviraptorids indicates that this care system evolved before the emergence of birds and represents birds ’ ancestral condition. In extant birds and over most adult sizes, paternal and biparental care correspond to the largest and smallest relative clutch volumes, respectively. of nearly all Paleognathes (ratites, tinamous) incubate and care for the young alone (4). Cretaceous troodontid and oviraptorid dinosaurs

David J. Varricchio; Jason R. Moore; Gregory M. Erickson; Mark A. Norell; Frankie D. Jackson; John J. Borkowski

2009-01-01

369

Revisiting the Estimation of Dinosaur Growth Rates  

PubMed Central

Previous growth-rate studies covering 14 dinosaur taxa, as represented by 31 data sets, are critically examined and reanalyzed by using improved statistical techniques. The examination reveals that some previously reported results cannot be replicated by using the methods originally reported; results from new methods are in many cases different, in both the quantitative rates and the qualitative nature of the growth, from results in the prior literature. Asymptotic growth curves, which have been hypothesized to be ubiquitous, are shown to provide best fits for only four of the 14 taxa. Possible reasons for non-asymptotic growth patterns are discussed; they include systematic errors in the age-estimation process and, more likely, a bias toward younger ages among the specimens analyzed. Analysis of the data sets finds that only three taxa include specimens that could be considered skeletally mature (i.e., having attained 90% of maximum body size predicted by asymptotic curve fits), and eleven taxa are quite immature, with the largest specimen having attained less than 62% of predicted asymptotic size. The three taxa that include skeletally mature specimens are included in the four taxa that are best fit by asymptotic curves. The totality of results presented here suggests that previous estimates of both maximum dinosaur growth rates and maximum dinosaur sizes have little statistical support. Suggestions for future research are presented. PMID:24358133

Myhrvold, Nathan P.

2013-01-01

370

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

Vršanský, Peter; van de Kamp, Thomas; Azar, Dany; Prokin, Alexander; Vidli?ka, L'ubomír; Vagovi?, Patrik

2013-01-01

371

"Teachosaurus" and "Learnoceratops": Dinosaurs as a Motivating Cross-Curricular Theme  

ERIC Educational Resources Information Center

The author takes a look into the benefits that dinosaurs may bring to the classroom. He discusses how he used dinosaurs as a cross-curricular theme to improve children's understanding and knowledge of science concepts. To investigate what a child might learn from dinosaurs, he started by comparing the many non-fiction dinosaur books using the…

Duggan, Denis

2011-01-01

372

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

373

The distribution of integumentary structures in a feathered dinosaur  

Microsoft Academic Search

Non-avian theropod dinosaurs with preserved integumentary coverings are becoming more common; but apart from the multiple specimens of Caudipteryx, which have true feathers, animals that are reasonably complete and entirely articulated that show these structures in relation to the body have not been reported. Here we report on an enigmatic small theropod dinosaur that is covered with filamentous feather-like structures

Qiang Ji; Mark A. Norell; Ke-Qin Gao; Shu-An Ji; Dong Ren

2001-01-01

374

Young Scientists Explore Dinosaurs. Book 8 Primary Level.  

ERIC Educational Resources Information Center

Designed to present interesting facts about science and to heighten the curiosity of primary age students, this book contains activities about the natural world and numerous black and white illustrations. Activities that focus on the dinosaur are organized into five sections. These include: (1) "Dinosaur Facts/Then and Now" (exploring bird and…

Penn, Linda

375

"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.

376

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

377

Dinosaurs in the Dark: Grades K-1: Text Only Version  

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 a PDF containing the informational text and a glossary.

Fries-Gaither, Jessica

378

Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus  

Microsoft Academic Search

BackgroundExtended neoteny and late stage allometric growth increase morphological disparity between growth stages in at least some dinosaurs. Coupled with relatively low dinosaur density in the Upper Cretaceous of North America, ontogenetic transformational representatives are often difficult to distinguish. For example, many hadrosaurids previously reported to represent relatively small lambeosaurine species were demonstrated to be juveniles of the larger taxa.

John R. Horner; Mark B. Goodwin; Paul Sereno

2009-01-01

379

A Diverse Assemblage of Late Cretaceous Dinosaur and Bird  

E-print Network

A Diverse Assemblage of Late Cretaceous Dinosaur and Bird Feathers from Canadian Amber Ryan C. Mc and underwater diving had evolved in Late Cretaceous birds. Because amber preserves feather structure filamentous structures similar to the protofeathers of nonavian dinosaurs that are unknown in mod- ern birds

Machel, Hans

380

A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs  

PubMed Central

Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates. PMID:22628475

Pol, Diego; Rauhut, Oliver W. M.

2012-01-01

381

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

382

FARLOW AND HOLTZ — PREDATION IN DINOSAURS THE FOSSIL RECORD OF PREDATION IN DINOSAURS  

E-print Network

ABSTRACT—Predatory theropod dinosaurs can usually be identified as such by features of their jaws, teeth, and postcrania, but different clades of these reptiles differed in their adaptations for prey handling. Inferences about theropod diets and hunting behavior based on functional morphology are sometimes supported by evidence from taphonomic associations with likely prey species, bite marks, gut contents, coprolites, and trackways. Very large theropods like Tyrannosaurus are unlikely to have been pure hunters or scavengers, and probably ate whatever meat they could easily obtain, dead or alive. Theropods were not the only dinosaur hunters, though; other kinds of large reptiles undoubtedly fed on dinosaurs as well. The taxonomic composition of dinosaurian predator-prey complexes varies as a function of time and geography, but an ecologically remarkable feature of dinosaurian faunas, as compared with terrestrial mammalian faunas, is the very large size commonly attained by both herbivorous and carnivorous dinosaurs. The K/T extinction event(s) did not end dinosaurian predation, because carnivorous birds remained prominent predators throughout the Cenozoic Era

James O. Farlow; Thomas; R. Holtz

383

A Theropod Dinosaur Embryo and the Affnities of the Flaming Cliffs Dinosaur Eggs  

Microsoft Academic Search

An embryonic skeleton of a nonavian theropod dinosaur was found preserved in an egg from Upper Cretaceous rocks in the Gobi Desert of Mongolia. Cranial features identify the embryo as a member of Oviraptoridae. Two embryo-sized skulls of dromaeosaurids, similar to that of Velociraptor, were also recovered in the nest. The eggshell microstructure is similar to that of ratite birds

Mark A. Norell; James M. Clark; Dashzeveg Demberelyin; Barsbold Rhinchen; Luis M. Chiappe; Amy R. Davidson; Malcolm C. McKenna; Perle Altangerel; Michael J. Novacek

1994-01-01

384

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

385

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.

2007-01-01

386

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.

387

A stop-EGFP transgenic mouse to detect clonal cell lineages generated by mutation  

E-print Network

A stop-EGFP transgenic mouse to detect clonal cell lineages generated by mutation Simon Ro+ & Bruce to be traced in virtually any tissue. A green fluorescent cell lineage is generated by a random mutation. The transgenic system allows efficient detection of mutations and stem-cell fate mapping in the epidermis using

388

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

389

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

390

Replicators, lineages, and interactors.  

PubMed

The target article argues that whole groups can act as interactors in an evolutionary process. We believe that Smaldino's discussion would be advanced by a more thorough analysis of the appropriate replicators and lineages for this model. We show that cultural evolution is necessarily a separate process from cultural group selection, and we also illustrate that the two processes may influence each other as demonstrated by an agent-based model of communicating food-processing skills. PMID:24970423

Taylor, Daniel J; Bryson, Joanna J

2014-06-01

391

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

392

Eggs tell story of baby dinosaurs' first steps  

NSDL National Science Digital Library

Scientists have discovered fossilized eggs containing developing dinosaurs that probably started out moving around on all four limbs before learning to walk only on only two legs -- kind of like people.

American Association for the Advancement of Science (AAAS;)

2005-07-28

393

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

394

Fossil Footprints: How Fast Was That Dinosaur Moving?  

ERIC Educational Resources Information Center

Describes an activity in which students construct relationships between their leg lengths, stride lengths, and movements in order to estimate the speeds of the dinosaurs that made various fossilized tracks. (WRM)

Caton, Randall; Otts, Charlotte

1999-01-01

395

A new giant carnivorous dinosaur from the Cretaceous of Patagonia  

Microsoft Academic Search

LARGE carnivorous animals, the top members of the trophic chain, are rare, and flesh-eating dinosaurs were rarer still. For years the only known giant theropods were Tyrannosaums rex1 and the poorly known Deinocheirus mirificus2, both from the Northern Hemisphere, but many important new dinosaurs have been dis-covered in the Southern Hemisphere during the past decade, con-siderably increasing our knowledge of

Rodolfo A. Coria; Leonardo Salgado

1995-01-01

396

Introduction to the Hadrosaurs: "Duck-billed" Dinosaurs  

NSDL National Science Digital Library

Hadrosaurs, the "duckbilled dinosaurs", were common in the Upper Cretaceous of Europe, Asia, and North America. They were members of the Ornithopoda, and close relatives and possibly descendants of the earlier iguanodontid dinosaurs. The morphology of the two subfamilies, Lambeosaurinae and Hadrosaurinae, is discussed, including the purpose of the crest on the head of the former. Two other fossils are also described, Edmontosaurus and a baby Maiasaura.

397

Dinosaurs in the Dark: Grades 2-3: 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 grade two through grade three 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

398

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

399

Broad-Scale Patterns of Late Jurassic Dinosaur  

E-print Network

Background: There have been numerous studies on dinosaur biogeographic distribution patterns. However, these distribution data have not yet been applied to ecological questions. Ecological studies of dinosaurs have tended to focus on reconstructing individual taxa, usually through comparisons to modern analogs. Fewer studies have sought to determine if the ecological structure of fossil assemblages is preserved and, if so, how dinosaur communities varied. Climate is a major component driving differences between communities. If the ecological structure of a fossil locality is preserved, we expect that dinosaur assemblages from similar environments will share a similar ecological structure. Methodology/Principal Findings: This study applies Ecological Structure Analysis (ESA) to a dataset of 100+ dinosaur taxa arranged into twelve composite fossil assemblages from around the world. Each assemblage was assigned a climate zone (biome) based on its location. Dinosaur taxa were placed into ecomorphological categories. The proportion of each category creates an ecological profile for the assemblage, which were compared using cluster and principal components analyses. Assemblages grouped according to biome, with most coming from arid or semi-arid/seasonal climates. Differences between assemblages are tied to the proportion of large high-browsing vs. small ground-foraging herbivores, which separates arid from semi-arid and moister environments, respectively. However, the effects of historical, taphonomic, and other environmental factors are still evident.

Christopher R. Noto; Ari Grossman

400

Regulation of macrophage and dendritic cell responses by their lineage precursors  

PubMed Central

Tissue macrophages and dendritic cells derive from hematopoietic stem cells, which exist in the bone marrow and generate intermediate precursor populations with increasingly restricted lineage potentials. There exists several precursors committed to the macrophage and dendritic cell lineages; these cells exhibit distinct tropism and function and respond differentially in pathophysiologic conditions. In this review, we consider experimental contexts in which macrophage and dendritic cell responses in tissue are not only dictated by the local environment, but also by the quantity and quality of newly recruited lineage precursor cells. Consequently, we discuss whether therapeutic control of macrophage and dendritic cell responses in tissue may be achieved through manipulation of their lineage precursors. PMID:22433183

Cortez-Retamozo, Virna; Etzrodt, Martin; Pittet, Mikael J.

2012-01-01

401

Contribution of Stem Cells to Kidney Repair  

Microsoft Academic Search

A current explanation for development of chronic renal injury is the imbalance between injurious mechanism and regenerative repair. The possibility that stem cells contribute to the repair of glomerular and tubular damage is of great interest for basic and translational research. Endogenous bone marrow-derived stem cells have been implicated in the repair of renal tissue, although the lineage of stem

Benedetta Bussolati; Peter Viktor Hauser; Raquel Carvalhosa; Giovanni Camussi

2009-01-01

402

Epithelial stem cells, wound healing and cancer  

Microsoft Academic Search

It is well established that tissue repair depends on stem cells and that chronic wounds predispose to tumour formation. However, the association between stem cells, wound healing and cancer is poorly understood. Lineage tracing has now shown how stem cells are mobilized to repair skin wounds and how they contribute to skin tumour development. The signalling pathways, including WNT and

Esther N. Arwert; Esther Hoste; Fiona M. Watt

2012-01-01

403

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

404

Heme compounds in dinosaur trabecular bone.  

PubMed

Six independent lines of evidence point to the existence of heme-containing compounds and/or hemoglobin breakdown products in extracts of trabecular tissues of the large theropod dinosaur Tyrannosaurus rex. These include signatures from nuclear magnetic resonance and electron spin resonance that indicate the presence of a paramagnetic compound consistent with heme. In addition, UV/visible spectroscopy and high performance liquid chromatography data are consistent with the Soret absorbance characteristic of this molecule. Resonance Raman profiles are also consistent with a modified heme structure. Finally, when dinosaurian tissues were extracted for protein fragments and were used to immunize rats, the resulting antisera reacted positively with purified avian and mammalian hemoglobins. The most parsimonious explanation of this evidence is the presence of blood-derived hemoglobin compounds preserved in the dinosaurian tissues. PMID:9177210

Schweitzer, M H; Marshall, M; Carron, K; Bohle, D S; Busse, S C; Arnold, E V; Barnard, D; Horner, J R; Starkey, J R

1997-06-10

405

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 Willem.

406

Dinoviz: Exploring the History and Nature of Science Through the Progression of Dinosaur Visualization  

NSDL National Science Digital Library

Dinosaurs in the middle school classroom can be exciting. These extinct reptiles are both an exotic subject and familiar to our students. Because students are inherently interested, dinosaurs can serve as an effective portal for the integration of biology

James Wandersee

2011-02-01

407

HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007  

E-print Network

1 HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007 Critical...) But how can we determine how extinct dinosaurs moved and operated in the living world? One approach

Holtz Jr., Thomas R.

408

Tracing the Tumor Lineage  

PubMed Central

Defining the pathways through which tumors progress is critical to our understanding and treatment of cancer. We do not routinely sample patients at multiple time points during the progression of their disease, and thus our research is limited to inferring progression a posteriori from the examination of a single tumor sample. Despite this limitation, inferring progression is possible because the tumor genome contains a natural history of the mutations that occur during the formation of the tumor mass. There are two approaches to reconstructing a lineage of progression: (1) inter-tumor comparisons, and (2) intra-tumor comparisons. The inter-tumor approach consists of taking single samples from large collections of tumors and comparing the complexity of the genomes to identify early and late mutations. The intra-tumor approach involves taking multiple samples from individual heterogeneous tumors to compare divergent clones and reconstruct a phylogenetic lineage. Here we discuss how these approaches can be used to interpret the current models for tumor progression. We also compare data from primary and metastatic copy number profiles to shed light on the final steps of breast cancer progression. Finally, we discuss how recent technical advances in single cell genomics will herald a new era in understanding the fundamental basis of tumor heterogeneity and progression. PMID:20537601

Navin, Nicholas E.; Hicks, James

2010-01-01

409

SMOOTH MUSCLE STEM CELLS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Vascular smooth muscle cells (SMCs) originate from multiple types of progenitor cells. In the embryo, the most well-studied SMC progenitor is the cardiac neural crest stem cell. Smooth muscle differentiation in the neural crest lineage is controlled by a combination of cell intrinsic factors, includ...

410

Homology of the palpebral and origin of supraorbital ossifications in ornithischian dinosaurs  

E-print Network

Homology of the palpebral and origin of supraorbital ossifications in ornithischian dinosaurs and origin of supraor- bital ossifications in ornithischian dinosaurs. Lethaia, 10.1111/j.1502 dinosaurs and its presence is considered a synapomorphy of the clade. By contrast, other ornithischians lack

411

HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007  

E-print Network

HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007 Preliminary:xxx-xxx. Prasad, V., C.A.E. Strömberg, H. Alimohammadian & A. Sahni. 2005. Dinosaur coprolites and the early. Cannibalism in the Madagascan dinosaur Majungatholus atopus. Nature 422:515-518. TOPIC 2: Trace Fossil

Holtz Jr., Thomas R.

412

HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007  

E-print Network

1 HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007 Critical of dinosaur fossils merely in terms of body fossils: skeletons and isolated teeth and bones. But trace fossils of dinosaurs. After all, while body fossils are parts of dead individuals, trace fossils were made

Holtz Jr., Thomas R.

413

HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007  

E-print Network

1 HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007 Critical and scary, the most important thing about dinosaurs that the general public knows is that they died off was the extinction of the non-avian dinosaurs catastrophic? The extinction event between the Maastrichtian Age

Holtz Jr., Thomas R.

414

CONSTRAINT-BASED EXCLUSION OF LIMB POSES FOR RECONSTRUCTING THEROPOD DINOSAUR LOCOMOTION  

E-print Network

ARTICLE CONSTRAINT-BASED EXCLUSION OF LIMB POSES FOR RECONSTRUCTING THEROPOD DINOSAUR LOCOMOTION limb of Tyrannosaurus rex and three other non-avian thero- pod dinosaurs at mid-stance of locomotion-based exclusion is a transparent, reproducible framework for evaluating functional hypotheses in dinosaurs

Hutchinson, John

415

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 unknown in dinosaurs), seemingly solid centra and limb bones (atypical for theropods), and accessory

Hutchinson, John

416

A new large-bodied theropod dinosaur from the Middle Jurassic of Warwickshire, United Kingdom  

E-print Network

A new large-bodied theropod dinosaur from the Middle Jurassic of Warwickshire, United Kingdom ROGER dinosaur from the Middle Jurassic of Warwickshire, United Kingdom. Acta Palaeontologica Polonica 55 (1): 35-bodied theropod dinosaur, distinct from the contemporaneous Megalosaurus bucklandii. Cruxicheiros newmanorum gen

Cambridge, University of

417

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. Keywords: Chile; Dinosaur footprints; Parabrontopodus; Sauropod; Upper Jurassic Resu´men En el presente

Benton, Michael

418

HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007  

E-print Network

1 HONR 259C: "Fearfully Great Lizards": Topics in Dinosaur Research Spring Semester 2007 Critical Review IV: Dinosaur Growth and Behavior DUE: Thursday April 19 Overview Sometimes people tend to think of dinosaurs--or other animals, for that matter--as if they were only adults. Yet all animals start off

Holtz Jr., Thomas R.

419

Predation upon Hatchling Dinosaurs by a New Snake from the Late Cretaceous of India  

E-print Network

Predation upon Hatchling Dinosaurs by a New Snake from the Late Cretaceous of India Jeffrey A India. S. indicus was fossilized in association with a sauropod dinosaur egg clutch, coiled around and demonstrate predation risks for hatchling sauropod dinosaurs. Our results suggest that large body size and jaw

Peters, Shanan E.

420

On the Meaning of Words and Dinosaur Bones: Lexical Knowledge Without a Lexicon  

E-print Network

On the Meaning of Words and Dinosaur Bones: Lexical Knowledge Without a Lexicon Jeffrey L. Elman to Hebb's (1949) paleontologist, who uses his beliefs and knowledge about dinosaurs in conjunction- tologist, and the dinosaur, to the meaning conveyed through these clues. (p. 140) David Rumelhart (1979) 1

Elman, Jeff

421

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. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus1

Cai, Long

422

Detecting Dinosaur DNA The fact that DNA sequence can be ob-  

E-print Network

N COMMEN Detecting Dinosaur DNA The fact that DNA sequence can be ob- tained from fossil organisms fragments ap- parently from a dinosaur that lived 80 mil- lion years ago (2). However, the likely source (1). In the case of a possible dinosaur sequence, there is strong evidence from morphology that birds

Hedges, Blair

423

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 characteristic features of the ceratosaur theropods, a group of medium-sized predatory dinosaurs that were

Benton, Michael

424

A reassessment of Kelmayisaurus petrolicus, a large theropod dinosaur from the Early Cretaceous of China  

E-print Network

A reassessment of Kelmayisaurus petrolicus, a large theropod dinosaur from the Early Cretaceous. 2012. A reassessment of Kelmayisaurus petrolicus, a large theropod dinosaur from the Early Cretaceous-bodied theropods from Asia is poor, hindering comparison of Asian predatory dinosaur faunas with those from other

Cambridge, University of

425

DinoViz: Exploring the History and Nature of Science through the Progression of Dinosaur Visualization  

ERIC Educational Resources Information Center

Dinosaurs in the middle school classroom can be exciting. These extinct reptiles are both an exotic subject and familiar to our students. Because students are inherently interested, dinosaurs can serve as an effective portal for the integration of biology, geology, ecology, and the history and nature of science. The field of dinosaur study is…

Clary, Renee; Wandersee, James

2011-01-01

426

L E T T E R Bizarre structures in dinosaurs: species recognition or  

E-print Network

L E T T E R Bizarre structures in dinosaurs: species recognition or sexual selection? A response' struc- tures) of dinosaurs ­ for example, the horns and frills of ceratopsids, the crests examples of exaggerated structures among dinosaurs pass both of these tests, indicating that species

Knell, Rob

427

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

428

Online Courses: AMNH Seminars on Science: The Link Between Dinosaurs and Birds  

NSDL National Science Digital Library

Did dinosaurs really go extinct 65 million years ago? Overwhelming evidence suggests that one branch of the dinosaur family tree managed to survive, and that we see living dinosaurs every day. We call them birds. In this course, equipped with paleontologi

1900-01-01

429

Lineage specificity of primary cilia in the mouse embryo.  

PubMed

Primary cilia are required for vertebrate cells to respond to specific intercellular signals. Here we define when and where primary cilia appear in the mouse embryo using a transgenic line that expresses ARL13B-mCherry in cilia and Centrin 2-GFP in centrosomes. Primary cilia first appear on cells of the epiblast at E6.0 and are subsequently present on all derivatives of the epiblast. In contrast, extraembryonic cells of the visceral endoderm and trophectoderm lineages have centrosomes but no cilia. Stem cell lines derived from embryonic lineages recapitulate the in vivo pattern: epiblast stem cells are ciliated, whereas trophoblast stem cells and extraembryonic endoderm (XEN) stem cells lack cilia. Basal bodies in XEN cells are mature and can form cilia when the AURKA-HDAC6 cilium disassembly pathway is inhibited. The lineage-dependent distribution of cilia is stable throughout much of gestation, defining which cells in the placenta and yolk sac are able to respond to Hedgehog ligands. PMID:25599390

Bangs, Fiona K; Schrode, Nadine; Hadjantonakis, Anna-Katerina; Anderson, Kathryn V

2015-02-01

430

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

431

Diachronism between extinction time of terrestrial and marine dinosaurs  

NASA Technical Reports Server (NTRS)

The dinosaur eggs of southern France occur in continental, fine-grained red-beds, rich in carbonate. The last eggs in the region occur in the magnetic polarity interval 30 normal. Estimates of the accumulation rate of these sediments on the basis of the magneto-stratigraphy leads to placement of the time of disappearance of the dinosaurs in this region of 200,000 to 400,000 years earlier than the Cretaceous-Tertiary boundary. In the Red Deer Valley, Canada, estimates of average accumulation rate lead to a time of disappearance of the dinosaurs of 135,000 to 157,000 years earlier than the Cretaceous-Tertiary boundary. In the central part of Poland, in the Nasilow Quarry, the paleomagnetic pattern shows 7 m of chalk of reversed polarity containing in its upper part the marine Cretaceous-Tertiary biostratigraphic boundary. A greensand deposit contains numerous re-deposited Maastrichtian fossils. The fossils show no signs of wear and are of very different sizes including 1 mm thick juvenile belemnites. The deposit was described as a lag-sediment. Among the various fossils are teeth of mosasaurs. Thus there is coincidence in time between the extinction of mosasaurs and other Cretaceous organisms. This leads to the conclusion, that extinction of terrestrial dinosaurs took place earlier than extinction of marine dinosaurs at the Cretaceous-Tertiary boundary.

Hansen, H. J.

1988-01-01

432

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

433

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

434

Observations on continuously growing roots of the sloth and the K14-Eda transgenic mice indicate that epithelial stem cells can give rise to both the ameloblast and root epithelium cell lineage creating distinct tooth patterns.  

PubMed

Root development is traditionally associated with the formation of Hertwig's epithelial root sheath (HERS), whose fragments give rise to the epithelial cell rests of Malassez (ERM). The HERS is formed by depletion of the core of stellate reticulum cells, the putative stem cells, in the cervical loop, leaving only a double layer of the basal epithelium with limited growth capacity. The continuously growing incisor of the rodent is subdivided into a crown analog half on the labial side, with a cervical loop containing a large core of stellate reticulum, and its progeny gives rise to enamel producing. The lingual side is known as the root analog and gives rise to ERM. We show that the lingual cervical loop contains a small core of stellate reticulum cells and suggest that it acts as a functional stem cell niche. Similarly we show that continuously growing roots represented by the sloth molar and K14-Eda transgenic incisor maintain a cervical loop with a small core of stellate reticulum cells around the entire circumference of the tooth and do not form a HERS, and still give rise to ERM. We propose that HERS is not a necessary structure to initiate root formation. Moreover, we conclude that crown vs. root formation, i.e. the production of enamel vs. cementum, and the differentiation of the epithelial cells into ameloblasts vs. ERM, can be regulated independently from the regulation of stem cell maintenance. This developmental flexibility may underlie the developmental and evolutionary diversity in tooth patterning. PMID:18315812

Tummers, Mark; Thesleff, Irma

2008-01-01

435

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

436

Lineage selection and plasticity in the intestinal crypt  

PubMed Central

We know more about the repertoire of cellular behaviours that define the stem and progenitor cells maintaining the intestinal epithelium than any other renewing tissue. Highly dynamic and stochastic processes define cell renewal. Historically the commitment step in differentiation is viewed as a ratchet, irreversibly promoting a given fate and corresponding to a programme imposed at the point of cell division. However, the emerging view of intestinal self-renewal is one of plasticity in which a stem cell state is easily reacquired. The pathway mediators of lineage selection are largely known but how they interface within highly dynamic populations to promote different lineages and yet permit plasticity is not. Advances in understanding gene regulation in the nervous system suggest possible mechanisms. PMID:25083805

Philpott, Anna; Winton, Douglas J

2014-01-01

437

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

438

Elementary School Educator's Guide to the Dinosaur Halls  

NSDL National Science Digital Library

The Museum's two Dinosaur Halls follow the evolutionary development of two distinct groups of dinosaurs, the Sauriscans and Ornithischians. This comprehensive guide to the halls' resources is designed to help you maximize your trip to the Museum. It includes detailed background information about the Museum's collection, a map of the Dinosaur Halls that shows the location of the exhibits and specimens that are highlighted on the elementary school tour and several pre-, during-, and post-visit activities to do with your students. There is a listing of related Museum exhibits and suggestions for how to tie them into your field trip and notes about how the topics featured in the halls address performance standards and curriculum requirements.

439

Global aspects of dinosaur distribution and evolution  

SciTech Connect

Late Jurassic dinosaurian assemblages show close taxonomic correspondence over wide geographical ranges. Presently available if meager evidence suggests that this is also the case for Early Cretaceous communities. Cretaceous dinosaurian assemblages of Campanian and Maastrichtian age show considerable geographical differentiation but also some wide-ranging genera. Northern Hemisphere terrestrial ecosystems were dominated by hadrosaurs and ceratopsians, both herbivores with advanced capabilities for oral food-processing, whereas Southern Hemisphere biota were characterized by the abundance of titanosaurid sauropods, which relied on gut processing. Very close taxonomic similarities exist between the Campanian and early Maastrichtian dinosaurian assemblages of Mongolia and western North America, which, in part, is matched by similarities among other tetrapods such as mammals. Endemic dinosaurs in the Southern Hemisphere appear to reflect major changes in continental configuration. Some evidence exists for interchange of fuanal elements between North and South America. In absence of late Maastrichtian dinosaurian assemblages from most regions, scenarios concerning the terminal Cretaceous extinction of the Dinosauria should be regarded with caution because they are exclusively based on the conditions in western North America.

Sues, H.

1988-02-01

440

Epigenetic regulation in adult stem cells and cancers  

PubMed Central

Adult stem cells maintain tissue homeostasis by their ability to both self-renew and differentiate to distinct cell types. Multiple signaling pathways have been shown to play essential roles as extrinsic cues in maintaining adult stem cell identity and activity. Recent studies also show dynamic regulation by epigenetic mechanisms as intrinsic factors in multiple adult stem cell lineages. Emerging evidence demonstrates intimate crosstalk between these two mechanisms. Misregulation of adult stem cell activity could lead to tumorigenesis, and it has been proposed that cancer stem cells may be responsible for tumor growth and metastasis. However, it is unclear whether cancer stem cells share commonalities with normal adult stem cells. In this review, we will focus on recent discoveries of epigenetic regulation in multiple adult stem cell lineages. We will also discuss how epigenetic mechanisms regulate cancer stem cell activity and probe the common and different features between cancer stem cells and normal adult stem cells. PMID:24172544

2013-01-01

441

Lineage dependency and lineage-survival oncogenes in human cancer  

Microsoft Academic Search

Although cell-lineage and differentiation models dominate tumour classification and treatment, the recognition that cancer is also a genomic disease has prompted a reconfiguration of cancer taxonomies according to molecular criteria. Recent evidence indicates that a synthesis of lineage-based and genetic paradigms might offer new insights into crucial and therapeutically pliable tumour dependencies. For example, MITF (microphthalmia-associated transcription factor), which is

William R. Sellers; Levi A. Garraway

2006-01-01

442

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

443

The first record of a sauropod dinosaur from Antarctica  

NASA Astrophysics Data System (ADS)

Sauropoda is one of the most diverse and geographically widespread clades of herbivorous dinosaurs, and until now, their remains have now been recovered from all continental landmasses except Antarctica. We report the first record of a sauropod dinosaur from Antarctica, represented by an incomplete caudal vertebra from the Late Cretaceous of James Ross Island. The size and morphology of the specimen allows its identification as a lithostrotian titanosaur. Our finding indicates that advanced titanosaurs achieved a global distribution at least by the Late Cretaceous.

Cerda, Ignacio A.; Paulina Carabajal, Ariana; Salgado, Leonardo; Coria, Rodolfo A.; Reguero, Marcelo A.; Tambussi, Claudia P.; Moly, Juan J.

2012-01-01

444

Scaling in Theropod Dinosaurs: Femoral Bone Strength and Locomotion  

NASA Astrophysics Data System (ADS)

In our first article1 on scaling in theropod dinosaurs, the longitudinal stress in the leg bones due to supporting the weight of the animal was studied and found not to control the dimensions of the femur. As a continuation of our study of elasticity in dinosaur bones, we now examine the transverse stress in the femur due to locomotion and find that this effect is important for the geometry of the bone. We find that larger theropods (including Tyrannosaurus rex) were less athletic than smaller theropods.

Lee, Scott

2015-02-01

445

Broad-Scale Patterns of Late Jurassic Dinosaur Paleoecology  

PubMed Central

Background There have been numerous studies on dinosaur biogeographic distribution patterns. However, these distribution data have not yet been applied to ecological questions. Ecological studies of dinosaurs have tended to focus on reconstructing individual taxa, usually through comparisons to modern analogs. Fewer studies have sought to determine if the ecological structure of fossil assemblages is preserved and, if so, how dinosaur communities varied. Climate is a major component driving differences between communities. If the ecological structure of a fossil locality is preserved, we expect that dinosaur assemblages from similar environments will share a similar ecological structure. Methodology/Principal Findings This study applies Ecological Structure Analysis (ESA) to a dataset of 100+ dinosaur taxa arranged into twelve composite fossil assemblages from around the world. Each assemblage was assigned a climate zone (biome) based on its location. Dinosaur taxa were placed into ecomorphological categories. The proportion of each category creates an ecological profile for the assemblage, which were compared using cluster and principal components analyses. Assemblages grouped according to biome, with most coming from arid or semi-arid/seasonal climates. Differences between assemblages are tied to the proportion of large high-browsing vs. small ground-foraging herbivores, which separates arid from semi-arid and moister environments, respectively. However, the effects of historical, taphonomic, and other environmental factors are still evident. Conclusions/Significance This study is the first to show that the general ecological structure of Late Jurassic dinosaur assemblages is preserved at large scales and can be assessed quantitatively. Despite a broad similarity of climatic conditions, a degree of ecological variation is observed between assemblages, from arid to moist. Taxonomic differences between Asia and the other regions demonstrate at least one case of ecosystem convergence. The proportion of different ecomorphs, which reflects the prevailing climatic and environmental conditions present during fossil deposition, may therefore be used to differentiate Late Jurassic dinosaur fossil assemblages. This method is broadly applicable to different taxa and times, allowing one to address questions of evolutionary, biogeographic, and climatic importance. PMID:20838442

Noto, Christopher R.; Grossman, Ari

2010-01-01

446

Cell Lineage Analysis of the Mammalian Female Germline  

PubMed Central

Fundamental aspects of embryonic and post-natal development, including maintenance of the mammalian female germline, are largely unknown. Here we employ a retrospective, phylogenetic-based method for reconstructing cell lineage trees utilizing somatic mutations accumulated in microsatellites, to study female germline dynamics in mice. Reconstructed cell lineage trees can be used to estimate lineage relationships between different cell types, as well as cell depth (number of cell divisions since the zygote). We show that, in the reconstructed mouse cell lineage trees, oocytes form clusters that are separate from hematopoietic and mesenchymal stem cells, both in young and old mice, indicating that these populations belong to distinct lineages. Furthermore, while cumulus cells sampled from different ovarian follicles are distinctly clustered on the reconstructed trees, oocytes from the left and right ovaries are not, suggesting a mixing of their progenitor pools. We also observed an increase in oocyte depth with mouse age, which can be explained either by depth-guided selection of oocytes for ovulation or by post-natal renewal. Overall, our study sheds light on substantial novel aspects of female germline preservation and development. PMID:22383887

Elbaz, Judith; Jinich, Adrian; Chapal-Ilani, Noa; Maruvka, Yosef E.; Nevo, Nava; Marx, Zipora; Horovitz, Inna; Wasserstrom, Adam; Mayo, Avi; Shur, Irena; Benayahu, Dafna; Skorecki, Karl; Segal, Eran; Dekel, Nava; Shapiro, Ehud

2012-01-01

447

Retinoids Accelerate B Lineage Lymphoid Differentiation  

PubMed Central

Retinoids are known to have potent effects on hematopoietic stem cell integrity, and our objective was to learn if they influence cells destined to replenish the immune system. Total CD19+ B lineage cells increased substantially in marrow and spleens of ATRA treated C57BL6 mice, while lymphoid progenitors were reduced. All B lymphoid progenitors were targets of ATRA in culture and overall cell yields declined without reductions in proliferation. Remarkably, ATRA shortened the time required for primitive progenitors to generate CD19+ cells. PCR analysis and a panel of RAR/RXR agonist treatments suggested that RAR? mediates these responses. The transcription factors EBF1 and Pax-5 were elevated during treatment and ATRA had similar effects on human B cell differentiation. That is, it inhibited the expansion of human progenitor cells and accelerated their differentiation to B lineage cells. There may be previously unsuspected side effects of ATRA therapy, and the new findings suggest retinoids can normally contribute to the lymphopoietic environment in bone marrow. PMID:18097013

Chen, Xinrong; Esplin, Brandt L.; Garrett, Karla P.; Welner, Robert S.; Webb, Carol F.

2008-01-01

448

Lineage determinants in early endocrine development  

PubMed Central

Pancreatic endocrine cells are produced from a dynamic epithelium in a process that, as in any developing organ, is driven by interacting programs of spatiotemporally regulated intercellular signals and autonomous gene regulatory networks. These algorithms work to push progenitors and their transitional intermediates through a series of railroad-station-like switching decisions to regulate flux along specific differentiation tracks. Extensive research on pancreas organogenesis over the last 20 years, greatly spurred by the potential to restore functional ?-cell mass in diabetic patients by transplantation therapy, is advancing our knowledge of how endocrine lineage bias is established and allocation is promoted. The field is working towards the goal of generating a detailed blueprint of how heterogeneous cell populations interact and respond to each other, and other influences such as the extracellular matrix, to move into progressively refined and mature cell states. Here, we highlight how signaling codes and transcriptional networks might determine endocrine lineage within a complex and dynamic architecture, based largely on studies in the mouse. The process begins with the designation of multipotent progenitor cells (MPC) to pancreatic buds that subsequently move through a newly proposed period involving epithelial plexus formation-remodeling, and ends with formation of clustered endocrine islets connected to the vascular and peripheral nervous systems. Developing this knowledge base, and increasing the emphasis on direct comparisons between mouse and human, will yield a more complete and focused picture of pancreas development, and thereby inform ?-cell-directed differentiation from human embryonic stem or induced pluripotent stem cells (hESC, iPSC). Additionally, a deeper understanding may provide surprising therapeutic angles by defining conditions that allow the controllable reprogramming of endodermal or pancreatic cell populations. PMID:22728667

Rieck, Sebastian; Bankaitis, Eric D.; Wright, Christopher V.E.

2013-01-01

449

An Early T Cell Lineage Commitment Checkpoint Dependent on the Transcription Factor Bcl11b  

PubMed Central

The identities of the regulators that mediate commitment of hematopoietic precursors to the T lymphocyte lineage have been unknown. The last stage of T lineage commitment in vivo involves mechanisms to suppress natural killer cell potential, to suppress myeloid and dendritic cell potential, and to silence the stem cell or progenitor cell regulatory functions that initially provide T cell receptor–independent self-renewal capability. The zinc finger transcription factor Bcl11b is T cell–specific in expression among hematopoietic cell types and is first expressed in precursors immediately before T lineage commitment. We found that Bcl11b is necessary for T lineage commitment in mice and is specifically required both to repress natural killer cell–associated genes and to down-regulate a battery of stem cell or progenitor cell genes at the pivotal stage of commitment. PMID:20595614

Li, Long; Leid, Mark; Rothenberg, Ellen V.

2010-01-01

450

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

451

Metric-Asaurus: Conceptualizing Scale Using Dinosaur Models  

ERIC Educational Resources Information Center

For middle school students who have seen only pictures of dinosaurs in books, in the movies, or on the internet, trying to comprehend the size of these gargantuan animals can be difficult. This lesson provides a way for students to visualize changing scale through studying extinct organisms and to gain a deeper understanding of the history of the…

Gloyna, Lisa; West, Sandra; Martin, Patti; Browning, Sandra

2010-01-01

452

Cretaceous age for the feathered dinosaurs of Liaoning, China  

Microsoft Academic Search

The ancient lake beds of the lower part of the Yixian Formation, Liaoning Province, northeastern China, have yielded a wide rangeof well-preserved fossils: the `feathered' dinosaurs Sinosauropteryx, Protarchaeopteryx and Caudipteryx, the primitive birds Confuciusornis and Liaoningornis, the mammal Zhangheotherium and the reportedly oldest flowering plant, Archaefructus. Equally well preserved in the lake beds are a wide range of fossil plants,

Carl C. Swisher; Yuan-Qing Wang; Xiao-Lin Wang; Xing Xu; Yuan Wang

1999-01-01

453

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

454

New dinosaurs link southern landmasses in the Mid-Cretaceous  

Microsoft Academic Search

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

Paul C. Sereno; Jeffrey A. Wilson; Jack L. Conrad

2004-01-01

455

Paleontology: a cock's comb on a duck-billed dinosaur.  

PubMed

A soft tissue structure has been discovered on the head of the duck-billed dinosaur Edmontosaurus. Its similarity to a cock's comb and other sexually dimorphic structures of birds suggests that potential sexual signals existed in these extinct animals. PMID:24456984

Horner, John R

2014-01-20

456

Growing up with dinosaurs: molecular dates and the mammalian radiation  

Microsoft Academic Search

Dates of divergence derived from molecular data have been used to place the beginning of the radiation of modern mammalian orders in the Cretaceous, long before the final extinction of the dinosaurs. These molecular dates have been used to challenge the idea that the ordinal diversification of mammals was triggered by the availability of ‘empty niches’ left vacant by the

Lindell Bromham; Matthew J. Phillips; David Penny

1999-01-01

457

TeV scale gravity, mirror universe, and ... dinosaurs  

E-print Network

This is somewhat extended version of the talk given at the Gran Sasso Summer Institute: Massive Neutrinos in Physics and Astrophysics. It describes general ideas about mirror world, extra spatial dimensions and dinosaur extinction. Some suggestions are made how these seemingly different things can be related to each other.

Z. K. Silagadze

2000-12-06

458

TeV scale gravity, mirror universe, and ... dinosaurs  

E-print Network

This is somewhat extended version of the talk given at the Gran Sasso SummerInstitute: Massive Neutrinos in Physics and Astrophysics. It describes generalideas about mirror world, extra spatial dimensions and dinosaur extinction.Some suggestions are made how these seemingly different things can be relatedto each other.

Silagadze, Z K

2001-01-01

459

Evidence for gregarious behavior and age segregation in sauropod dinosaurs  

Microsoft Academic Search

Both body fossil and ichnofossil evidence for gregarious behavior in sauropod dinosaurs is examined. Some localities suggest that herds were partitioned on the basis of age, whereas other sites reveal groups consisting of both adult and juvenile\\/subadult individuals. Two skeletal accumulations showing evidence of age segregation are examined in detail. The Mother's Day Quarry in the Upper Jurassic Morrison Formation

Timothy S. Myers; Anthony R. Fiorillo

2009-01-01

460

Reanalysis of ``Raptorex kriegsteini'': A Juvenile Tyrannosaurid Dinosaur from Mongolia  

Microsoft Academic Search

The carnivorous Tyrannosauridae are among the most iconic dinosaurs: typified by large body size, tiny forelimbs, and massive robust skulls with laterally thickened teeth. The recently described small-bodied tyrannosaurid Raptorex kreigsteini is exceptional as its discovery proposes that many of the distinctive anatomical traits of derived tyrannosaurids were acquired in the Early Cretaceous, before the evolution of large body size.

Denver W. Fowler; Holly N. Woodward; Elizabeth A. Freedman; Peter L. Larson; John R. Horner; Anjali Goswami

2011-01-01

461

Fossils and Dinosaurs--A Fully Integrated Instructional Unit.  

ERIC Educational Resources Information Center

This lesson plan for the second and third grades uses information on dinosaurs, their adaptations and survival, to provide science education for limited-English-proficient (LEP) students in San Diego, California. The primary text is "Los Dinosaurios Gigantes," a core literature book used in the school district. Lessons are based on the whole…

Kuehl, Matt; And Others

462

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

463

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