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Last update: November 12, 2013.
1

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.

Ptv, Idaho

2011-09-21

2

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

3

Dinosaurs  

NSDL National Science Digital Library

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

Stearns, Ms.

2008-10-26

4

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

5

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

6

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

7

Method for Modulating Epithelial Stem Cell Lineage.  

National Technical Information Service (NTIS)

The present invention relates to methods of modulating epithelial stem cell lineage by regulating the expression of Lef1 or a BMP inhibitor and/or the stability of beta-catenin or the expression of a Wnt; regulating the expression or activity of GATA-3; o...

C. Jamora C. Kaufman E. Fuchs K. Kobielak

2004-01-01

8

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

9

Perspective: stem cells react! Cell lineages as complex adaptive systems.  

PubMed

It may be argued that adult stem cell processes or, more precisely, the cell lineages that arise from them, represent complex reactive or adaptive systems. Approaching hematopoietic and other stem cell lineages from this perspective has direct bearing on current debates regarding the plasticity of these lineage systems as well as on interpretation and modeling of clinical data regarding many diseases. PMID:14725897

Theise, Neil D

2004-01-01

10

The Drosophila cyst stem cell lineage  

PubMed Central

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

Zoller, Richard; Schulz, Cordula

2012-01-01

11

Lineage Tracing of Tissue-Specific Stem Cells In Vivo  

Microsoft Academic Search

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

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

12

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

13

The liver as a stem cell and lineage system.  

PubMed

We propose that the liver is a stem cell and lineage system with many parallels to lineages in the bone marrow, gut, and epidermis, varying from them only in kinetics. All are organized with three compartments: a slow cycling stem cell compartment with cells expressing a fetal phenotype and responding slowly to injury; an amplification compartment with cells of intermediate phenotype rapidly proliferating in response to regenerative stimuli or acute injuries; and a terminal differentiation compartment in which cells increasingly differentiate and gradually lose their ability to divide. In all systems, both those with slow or rapid kinetics, the various compartments are positioned in a polarized organization, are associated with a gradient in the chemistry of the extracellular matrix, and show lineage-position-dependent growth responses, gene expression, pharmacological and toxicological responses, and reaction to viruses and radiation. In general, known oncogens selectively kill cells in the differentiation compartment inducing chronic regenerative responses of the cells in stem cell and/or amplification compartment. Tumors arise by subsequent transformation of the activated stem cells or early precursor cells. The evidence for a lineage model consists of the data implicating gradients in cell size, ploidy, growth potential, and antigenic and gene expression in the liver parenchyma along the sinusoidal plates. The traditional explanation for this heterogeneity is that it represents adaption of cells to a changing sinusoidal microenvironment dictated by the direction of blood flow. However, we review the extant data and suggest that it more readily supports a lineage model involving a maturation process beginning with stem cells and precursors in the periportal zone and ending with sensescing parenchyma near the central vein. Support for this theory is provided by the studies on phenotypic heterogeneity in liver, investigations into the embryology of the liver, and analyses of the responses of liver to chemical and viral oncogens that induce rapid proliferation of small cells with oval-shaped nuclei, "oval cells," now thought to be closely related to liver stem cells. The lineage model provides clarity and insights into many aspects of liver biology and disease including the limited proliferative ability of in vitro parenchymal cultures, liver regeneration, gene expression, viral infection, hepatocellular carcinogenesis, liver cell transplantation, and aging. PMID:1325126

Sigal, S H; Brill, S; Fiorino, A S; Reid, L M

1992-08-01

14

Epigenetic regulation of stem cells differentiating along the neural lineage.  

PubMed

Many lineage-specific genes are poised and silenced in stem cells. Upon differentiation, genes that are related to self-renewal and alternative lineages are stably silenced. CpG methylation at proximal promoters and PRC2-mediated H3K27me3 play a role in silencing genes temporarily or permanently, with or without coexistence of active epigenetic marks, respectively. Interestingly, DNA methylation on neuronal genes that is distal to transcription start site enable transcription activation owing to its ability to repel PRC2-mediated inhibition. In addition, DNA demethylase Tet proteins play a role in regulation of changes in DNA methylation and related H3K27me3 during differentiation. Collectively, a complex epigenetic network formed by H3K4me3, histone acetylation/deacetylation, H3K27me3 and DNA methylation/demethylation act together to regulate stem cell self-renewal and differentiation. PMID:22835699

Coskun, Volkan; Tsoa, Rosemarie; Sun, Yi E

2012-07-24

15

Two subpopulations of stem cells for T cell lineage  

SciTech Connect

An assay system for the stem cell that colonizes the thymus and differentiates into T cells was developed, and by using this assay system the existence of two subpopulations of stem cells for T cell lineage was clarified. Part-body-shielded and 900-R-irradiated C57BL/6 (H-2b, Thy-1.2) recipient mice, which do not require the transfer of pluripotent stem cells for their survival, were transferred with cells from B10 X Thy-1.1 (H-2b, Thy-1.1) donor mice. The reconstitution of the recipient's thymus lymphocytes was accomplished by stem cells in the donor cells and those spared in the shielded portion of the recipient that competitively colonize the thymus. Thus, the stem cell activity of donor cells can be evaluated by determining the proportion of donor-type (Thy-1.1+) cells in the recipient's thymus. Bone marrow cells were the most potent source of stem cells. By contrast, when the stem cell activity was compared between spleen and bone marrow cells of whole-body-irradiated (800 R) C57BL/6 mice reconstituted with B10 X Thy-1.1 bone marrow cells by assaying in part-body-shielded and irradiated C57BL/6 mice, the activity of these two organs showed quite a different time course of development. The results strongly suggest that the stem cells for T cell lineage in the bone marrow comprise at least two subpopulations, spleen-seeking and bone marrow-seeking cells.

Katsura, Y.; Amagai, T.; Kina, T.; Sado, T.; Nishikawa, S.

1985-11-01

16

Differentiation of Neural Lineage Cells from Human Pluripotent Stem Cells  

PubMed Central

Human pluripotent stem cells have the unique properties of being able to proliferate indefinitely in their undifferentiated state and to differentiate into any somatic cell type. These cells are thus posited to be extremely useful for furthering our understanding of both normal and abnormal human development, providing a human cell preparation that can be used to screen for new reagents or therapeutic agents, and generating large numbers of differentiated cells that can be used for transplantation purposes. Critical among the applications for the latter are diseases and injuries of the nervous system, medical approaches to which have been, to date, primarily palliative in nature. Differentiation of human pluripotent stem cells into cells of the neural lineage, therefore, has become a central focus of a number of laboratories. This has resulted in the description in the literature of several dozen methods for neural cell differentiation from human pluripotent stem cells. Among these are methods for the generation of such divergent neural cells as dopaminergic neurons, retinal neurons, ventral motoneurons, and oligodendroglial progenitors. In this review, we attempt to fully describe most of these methods, breaking them down into five basic subdivisions: 1) starting material, 2) induction of loss of pluripotency, 3) neural induction, 4) neural maintenance and expansion, and 5) neuronal/glial differentiation. We also show data supporting the concept that undifferentiated human pluripotent stem cells appear to have an innate neural differentiation potential. In addition, we evaluate data comparing and contrasting neural stem cells differentiated from human pluripotent stem cells with those derived directly from the human brain.

Schwartz, Philip H.; Brick, David J.; Stover, Alexander E.; Loring, Jeanne F.; Muller, Franz Josef

2008-01-01

17

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.

18

Generation of human embryonic stem cells carrying lineage specific reporters.  

PubMed

The distinctive properties of human embryonic stem cells (hESCs) enable them to provide unique models to study the network of signaling pathways that regulate organogenesis, generate disease models, produce cells and tissues for therapies, and identify new drugs for treatment. Genetic modification of hESCs is a powerful tool to assist the above studies. Generation of lineage-specific fluorescent protein reporter hESC lines will greatly benefit investigators to monitor specific cell lineages in a live, easy, and timely manner. This technique will facilitate high throughput screening to identify molecules important in regulating specific cell fate commitment. In addition, such reporter cell lines enable researchers to enrich certain cell populations by fluorescent activated cell sorting (FACS) for either downstream biological analysis or in vivo applications. We have shown that hESCs can be stably transfected with a plasmid in which expression of the green fluorescent protein (GFP) is under the control of the Oct-4 promoter using chemical transfection. The expression pattern of transgenic Oct-4-GFP reflects that of endogenous Oct-4. PMID:21042987

Noisa, Parinya; Urrutikoetxea-Uriguen, Alai; Cui, Wei

2011-01-01

19

Differentiation of human embryonic stem cells along a hepatic lineage.  

PubMed

The limited availability of hepatic tissue suitable for the treatment of liver disease and drug discovery research advances the generation of hepatic-like cells from alternative sources as a valuable approach. In this investigation we exploited a unique hepatic differentiation approach to generate hepatocyte-like cells from human embryonic stem cells (hESCs). hESCs were cultured for 10-20 days on collagen substrate in highly defined and serum free hepatocyte media. The resulting cell populations exhibited hepatic cell-like morphology and were characterized with a variety of biological endpoint analyses. Real-time PCR analysis demonstrated that mRNA expression of the 'stemness' marker genes NANOG and alkaline phosphatase in the differentiated cells was significantly reduced, findings that were functionally validated using alkaline phosphatase activity detection measures. Immunofluorescence studies revealed attenuated levels of the 'stemness' markers OCT4, SOX2, SSEA-3, TRA-1-60, and TRA-1-81 in the hepatic-like cell population. The hepatic character of the cells was evaluated additionally by real-time PCR analyses that demonstrated increased mRNA expression of the hepatic transcription factors FOXA1, C/EBP?, and HNF1?, the nuclear receptors CAR, RXR?, PPAR?, and HNF4?, the liver-generated plasma proteins ?-fetoprotein, transthyretin, transferrin, and albumin, the protease inhibitor ?-1-antitrypsin, metabolic enzymes HMGCS2, PEPCK, and biotransformation enzymes CYP3A7, CYP3A4, CYP3A5, and CYP2E1. Indocyanine green uptake albumin secretion and glycogen storage capacity further confirmed acquisition of hepatic function. These studies define an expeditious methodology that facilitates the differentiation of hESCs along a hepatic lineage and provide a framework for their subsequent use in pharmacological and toxicological research applications requiring a renewable supply of human hepatocytes. PMID:21241686

Zamule, Stephanie M; Coslo, Denise M; Chen, Fengming; Omiecinski, Curtis J

2011-01-15

20

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…

Nakamura, Sandra; Baptiste, H. Prentice

2006-01-01

21

Treatment of Cone Cell Degeneration with Transfected Lineage Negative Hematopoietic Stem Cells.  

National Technical Information Service (NTIS)

Transfected, mammalian, adult bone marrow-derived, lineage negative hematopoietic stem cell populations (Lin(sup -)HSCs) contain endothelial progenitor cells (EPCs) capable of rescuing retinal blood vessels and neuronal networks in the eye. Preferably at ...

A. Otani K. Da Silva M. Friedlander S. Moreno

2005-01-01

22

Isolated Lineage Negative Hematopoietic Stem Cells and Methods of Treatment Therewith.  

National Technical Information Service (NTIS)

Isolated, mammalian, adult bone marrow-derived, lineage negative hematopoietic stem cell populations (Lin(sup -) HSCs) contain endothelial progenitor cells (EPCs) capable of rescuing retinal blood vessels and neuronal networks in the eye. Preferably at le...

A. Otani K. Da Silva M. Friedlander S. H. Moreno

2004-01-01

23

Methods for Maintaining Hepatocytes in Culture and for Differentiating Embryonic Stem Cells along a Hepatocyte Lineage.  

National Technical Information Service (NTIS)

The invention provides methods and media for culturing embryonic stem (ES) cells, such as human ES cells, and directing them along the hepatic lineage. It further provides methods for maintaining hepatocytes in culture for extended periods. The invention ...

H. Shirahashi M. A. Zern

2004-01-01

24

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.

25

Epigenetic dynamics of stem cells and cell lineage commitment: digging Waddington's canal  

Microsoft Academic Search

Cells of the early mammalian embryo, including pluripotent embryonic stem (ES) cells and primordial germ cells (PGCs), are epigenetically dynamic and heterogeneous. During early development, this heterogeneity of epigenetic states is associated with stochastic expression of lineage-determining transcription factors that establish an intimate crosstalk with epigenetic modifiers. Lineage-specific epigenetic modification of crucial transcription factor loci (for example, methylation of the

Wendy Dean; Myriam Hemberger; Wolf Reik

2009-01-01

26

Scholastic: Dinosaurs  

NSDL National Science Digital Library

This website contains details and activities about dinosaurs. It covers the geologic time periods during which dinosaurs existed, a web-quest for dinosaur information, quizzes and games about various dinosaur topics, and research starters for projects and activities. For teachers, there are lesson plan suggestions, assessment ideas, and details for using this site in the classroom as a project. Links are provided for additional information.

27

Mapping differentiation pathways from hematopoietic stem cells using Flk2/Flt3 lineage tracing  

PubMed Central

Genetic fate-mapping approaches provide a unique opportunity to assess differentiation pathways under physiological conditions. We have recently employed a lineage tracing approach to define hematopoietic differentiation pathways in relation to expression of the tyrosine kinase receptor Flk2.1 Based on our examination of reporter activity across all stem, progenitor and mature populations in our Flk2-Cre lineage model, we concluded that all mature blood lineages are derived through a Flk2+ intermediate, both at steady-state and under stress conditions. Here, we re-examine in depth our initial conclusions and perform additional experiments to test alternative options of lineage specification. Our data unequivocally support the conclusion that onset of Flk2 expression results in loss of self-renewal but preservation of multilineage differentiation potential. We discuss the implications of these data for defining stem cell identity and lineage potential among hematopoietic populations.

Boyer, Scott W.; Beaudin, Anna E.; Forsberg, E. Camilla

2012-01-01

28

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

29

A Continuum of Cell States Spans Pluripotency and Lineage Commitment in Human Embryonic Stem Cells  

PubMed Central

Background Commitment in embryonic stem cells is often depicted as a binary choice between alternate cell states, pluripotency and specification to a particular germ layer or extraembryonic lineage. However, close examination of human ES cell cultures has revealed significant heterogeneity in the stem cell compartment. Methodology/Principal Findings We isolated subpopulations of embryonic stem cells using surface markers, then examined their expression of pluripotency genes and lineage specific transcription factors at the single cell level, and tested their ability to regenerate colonies of stem cells. Transcript analysis of single embryonic stem cells showed that there is a gradient and a hierarchy of expression of pluripotency genes in the population. Even cells at the top of the hierarchy generally express only a subset of the stem cell genes studied. Many cells co-express pluripotency and lineage specific genes. Cells along the continuum show a progressively decreasing likelihood of self renewal as their expression of stem cell surface markers and pluripotency genes wanes. Most cells that are positive for stem cell surface markers express Oct-4, but only those towards the top of the hierarchy express the nodal receptor TDGF-1 and the growth factor GDF3. Significance These findings on gene expression in single embryonic stem cells are in concert with recent studies of early mammalian development, which reveal molecular heterogeneity and a stochasticity of gene expression in blastomeres. Our work indicates that only a small fraction of the population resides at the top of the hierarchy, that lineage priming (co-expression of stem cell and lineage specific genes) characterizes pluripotent stem cell populations, and that extrinsic signaling pathways are upstream of transcription factor networks that control pluripotency.

Hough, Shelley R.; Laslett, Andrew L.; Grimmond, Sean B.; Kolle, Gabriel; Pera, Martin F.

2009-01-01

30

Human mesenchymal stem cells from adipose tissue: Differentiation into hepatic lineage  

Microsoft Academic Search

Adipose tissue represents an accessible source of mesenchymal stem cells (ADSCs), with similar characteristics to bone marrow-derived stem cells. The aim of this work was to investigate the transdifferentiation of ADSCs into hepatic lineage cells in vitro. ADSCs were obtained from human adipose tissue from lipectomy. Cells were grown in medium containing 15% AB human serum. Cultures were serum deprived

R. Taléns-Visconti; A. Bonora; R. Jover; V. Mirabet; F. Carbonell; J. V. Castell; M. J. Gómez-Lechón

2007-01-01

31

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.

32

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

Microsoft Academic Search

Hematopoietic stem cells sequentially pass through a series of decision points affecting self-renewal or lineage-specific differentiation. Notch1 receptor is a known modulator of lineage-specific events in hematopoiesis that we assessed in the context of in vivo stem cell kinetics. Us- ing RAG-12\\/2 mouse stems cells, we docu- mented increased stem cell numbers due to decreased differentiation and enhanced stem cell

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

2002-01-01

33

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

34

Dinosaur Sounds  

NSDL National Science Digital Library

Every wonder what a dinosaur sounded like? This radio broadcast reports on how computer scientists are now running computer programs to determine just what sounds could have been produced by a recently uncovered skull of a duck billed dinosaur. The scientists create a 3-D model of the dinosaur skull on the computer and simulate how sound waves bounce in the nasal passages. The clip is 2 minutes in length.

35

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.

1999-01-01

36

Cell-surface proteomics identifies lineage-specific markers of embryo-derived stem cells.  

PubMed

The advent of reprogramming and its impact on stem cell biology has renewed interest in lineage restriction in mammalian embryos, the source of embryonic (ES), epiblast (EpiSC), trophoblast (TS), and extraembryonic endoderm (XEN) stem cell lineages. Isolation of specific cell types during stem cell differentiation and reprogramming, and also directly from embryos, is a major technical challenge because few cell-surface proteins are known that can distinguish each cell type. We provide a large-scale proteomic resource of cell-surface proteins for the four embryo-derived stem cell lines. We validated 27 antibodies against lineage-specific cell-surface markers, which enabled investigation of specific cell populations during ES-EpiSC reprogramming and ES-to-XEN differentiation. Identified markers also allowed prospective isolation and characterization of viable lineage progenitors from blastocysts by flow cytometry. These results provide a comprehensive stem cell proteomic resource and enable new approaches to interrogate the mechanisms that regulate cell fate specification. PMID:22424930

Rugg-Gunn, Peter J; Cox, Brian J; Lanner, Fredrik; Sharma, Parveen; Ignatchenko, Vladimir; McDonald, Angela C H; Garner, Jodi; Gramolini, Anthony O; Rossant, Janet; Kislinger, Thomas

2012-03-15

37

Cell-Surface Proteomics Identifies Lineage-Specific Markers of Embryo-Derived Stem Cells  

PubMed Central

Summary The advent of reprogramming and its impact on stem cell biology has renewed interest in lineage restriction in mammalian embryos, the source of embryonic (ES), epiblast (EpiSC), trophoblast (TS), and extraembryonic endoderm (XEN) stem cell lineages. Isolation of specific cell types during stem cell differentiation and reprogramming, and also directly from embryos, is a major technical challenge because few cell-surface proteins are known that can distinguish each cell type. We provide a large-scale proteomic resource of cell-surface proteins for the four embryo-derived stem cell lines. We validated 27 antibodies against lineage-specific cell-surface markers, which enabled investigation of specific cell populations during ES-EpiSC reprogramming and ES-to-XEN differentiation. Identified markers also allowed prospective isolation and characterization of viable lineage progenitors from blastocysts by flow cytometry. These results provide a comprehensive stem cell proteomic resource and enable new approaches to interrogate the mechanisms that regulate cell fate specification.

Rugg-Gunn, Peter J.; Cox, Brian J.; Lanner, Fredrik; Sharma, Parveen; Ignatchenko, Vladimir; McDonald, Angela C.H.; Garner, Jodi; Gramolini, Anthony O.; Rossant, Janet; Kislinger, Thomas

2012-01-01

38

[Differentiation of pluripotent stem cells into pancreatic lineages].  

PubMed

Diabetes mellitus is the leading metabolic disease and represents a major public health concern worldwide. Whereas the transplantation of pancreas donor-derived islets significantly improves the quality of life of diabetic patients who become insulin independent for few years, it can unfortunately be provided only to few patients in an advanced stage of the disease. This situation is related to the severe shortage in pancreas donors and has prompted the hunt for alternative sources of islet cells. Beside many other strategies aiming at producing new beta cells in vitro or in vivo, a particular focus has been on the plupiropent stem cells because of their abundant availability and their extreme plasticity. Progress in understanding small vertebrates embryonic development has tremendously contributed to the design of differentiation strategies applied to pluripotent stem cells. Nowadays, definitive endoderm and pancreatic progenitors can be efficiently induced from human embryonic stem cells and from human induced pluripotent stem cells. Although we are still lacking the knowledge required for deriving functional beta cells in vitro, transplantation experiments have demonstrated that stem cell-derived pancreas progenitors further generate this phenotype in vivo. All these findings gathered during the last decade witness the closer clinical application of pluripotent stem cell progenies in diabetes cell therapy. PMID:24005628

Kunjom Mfopou, Josué; Bouwens, Luc

2013-09-05

39

Expression Profile of Genes Representing Varied Spectra of Cell Lineages in Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells  

Microsoft Academic Search

Bone marrow (BM) transplantation is a well-established classical treatment for children with malignant haematologic diseases including leukaemia or fatal metabolic diseases [1]. Mononuclear cells (MNCs) in human BM undergo haemopoiesis into distinct cell lineages such as haemopoietic stem cells and mesenchymal stem cells (MSCs), which are capable of differentiating into varied spectra of cell lineages [2, 3]. Human umbilical cord

Young Joon Moon; Myoung Woo Lee; Mal Sook Yang; Sun Kyung Kim; Joon Seong Park; Hugh C. Kim; Hy-Sook Kim; Kwang-Ho Lee; Young-Jin Kim; Jeongeun Choi

2005-01-01

40

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.

Munsart, Craig; Gundy, Karen A.

41

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.

42

Dinosaur Tracking.  

ERIC Educational Resources Information Center

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

Lockley, Martin

1984-01-01

43

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

44

Transcriptional analysis of early lineage commitment in human embryonic stem cells  

Microsoft Academic Search

BACKGROUND: The mechanisms responsible for the maintenance of pluripotency in human embryonic stem cells, and those that drive their commitment into particular differentiation lineages, are poorly understood. In fact, even our knowledge of the phenotype of hESC is limited, because the immunological and molecular criteria presently used to define this phenotype describe the properties of a heterogeneous population of cells.

Andrew L Laslett; Sean Grimmond; Brooke Gardiner; Lincon Stamp; Adelia Lin; Susan M Hawes; Sam Wormald; David Nikolic-Paterson; David Haylock; Martin F Pera

2007-01-01

45

Reduced Reactivation from Dormancy but Maintained Lineage Choice of Human Mesenchymal Stem Cells with Donor Age  

Microsoft Academic Search

Mesenchymal stem cells (MSC) are promising for cell-based regeneration therapies but up to date it is still controversial whether their function is maintained throughout ageing. Aim of this study was to address whether frequency, activation in vitro, replicative function, and in vitro lineage choice of MSC is maintained throughout ageing to answer the question whether MSC-based regeneration strategies should be

Verena Dexheimer; Sebastian Mueller; Frank Braatz; Wiltrud Richter

2011-01-01

46

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

47

Differentiation of Embryonic Stem Cells to Vascular Cell Lineages  

Microsoft Academic Search

\\u000a In the face of extraordinary advances in the ­prevention, diagnosis, and treatment of human diseases, devastating cardiopulmonary\\u000a diseases continue to deprive people of health. Research in developmental biology has led to the discovery of stem cells, which\\u000a provide a platform to understand the basic mechanism of those diseases and give a hope for potential clinical applications.\\u000a Three main types of

Andriana Margariti; Lingfang Zeng; Qingbo Xu

48

DNA methylation plasticity of human adipose-derived stem cells in lineage commitment.  

PubMed

Adult stem cells have an enormous potential for clinical use in regenerative medicine that avoids many of the drawbacks characteristic of embryonic stem cells and induced pluripotent stem cells. In this context, easily obtainable human adipose-derived stem cells offer an interesting option for future strategies in regenerative medicine. However, little is known about their repertoire of differentiation capacities, how closely they resemble the target primary tissues, and the potential safety issues associated with their use. DNA methylation is one of the most widely recognized epigenetic factors involved in cellular identity, prompting us to consider how the analyses of 27,578 CpG sites in the genome of these cells under different conditions reflect their different natural history. We show that human adipose-derived stem cells generate myogenic and osteogenic lineages that share much of the DNA methylation landscape characteristic of primary myocytes and osteocytes. Most important, adult stem cells and in vitro-generated myocytes and osteocytes display a significantly different DNA methylome from that observed in transformed cells from these tissue types, such as rhabdomyosarcoma and osteosarcoma. These results suggest that the plasticity of the DNA methylation patterns plays an important role in lineage commitment of adult stem cells and that it could be used for clinical purposes as a biomarker of efficient and safely differentiated cells. PMID:23031258

Berdasco, María; Melguizo, Consolación; Prados, Jose; Gómez, Antonio; Alaminos, Miguel; Pujana, Miguel A; Lopez, Miguel; Setien, Fernando; Ortiz, Raul; Zafra, Inma; Aranega, Antonia; Esteller, Manel

2012-09-29

49

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

PubMed

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

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

2012-05-26

50

A Computational Model for Understanding Stem Cell, Trophectoderm and Endoderm Lineage Determination  

PubMed Central

Background Recent studies have associated the transcription factors, Oct4, Sox2 and Nanog as parts of a self-regulating network which is responsible for maintaining embryonic stem cell properties: self renewal and pluripotency. In addition, mutual antagonism between two of these and other master regulators have been shown to regulate lineage determination. In particular, an excess of Cdx2 over Oct4 determines the trophectoderm lineage whereas an excess of Gata-6 over Nanog determines differentiation into the endoderm lineage. Also, under/over-expression studies of the master regulator Oct4 have revealed that some self-renewal/pluripotency as well as differentiation genes are expressed in a biphasic manner with respect to the concentration of Oct4. Methodology/Principal Findings We construct a dynamical model of a minimalistic network, extracted from ChIP-on-chip and microarray data as well as literature studies. The model is based upon differential equations and makes two plausible assumptions; activation of Gata-6 by Oct4 and repression of Nanog by an Oct4–Gata-6 heterodimer. With these assumptions, the results of simulations successfully describe the biphasic behavior as well as lineage commitment. The model also predicts that reprogramming the network from a differentiated state, in particular the endoderm state, into a stem cell state, is best achieved by over-expressing Nanog, rather than by suppression of differentiation genes such as Gata-6. Conclusions The computational model provides a mechanistic understanding of how different lineages arise from the dynamics of the underlying regulatory network. It provides a framework to explore strategies of reprogramming a cell from a differentiated state to a stem cell state through directed perturbations. Such an approach is highly relevant to regenerative medicine since it allows for a rapid search over the host of possibilities for reprogramming to a stem cell state.

Chickarmane, Vijay; Peterson, Carsten

2008-01-01

51

Dinosaur Journey  

NSDL National Science Digital Library

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

2011-06-14

52

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

53

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

54

ERG is required for the differentiation of embryonic stem cells along the endothelial lineage  

Microsoft Academic Search

BACKGROUND: The molecular mechanisms that govern stem cell differentiation along the endothelial lineage remain largely unknown. Ets related gene (ERG) has recently been shown to participate in the transcriptional regulation of a number of endothelial specific genes including VE-cadherin (CD144), endoglin, and von Willebrand's Factor (vWF). The specific role of the ETS factor ERG during endothelial differentiation has not been

Vesna Nikolova-Krstevski; Lei Yuan; Alexandra Le Bras; Preethi Vijayaraj; Maiko Kondo; Isabel Gebauer; Manoj Bhasin; Chris V Carman; Peter Oettgen

2009-01-01

55

Dinosaur Impressions  

NASA Astrophysics Data System (ADS)

Perhaps you are a paleontologist or have always wondered what it is like to be one. Or you are fascinated by fossils and like to read about the origins and natural history of dinosaurs. Or maybe you are an avid traveler and reader of travelogues. If you are any of these things, then this book is for you. Originally published in 1994 in French, Dinosaur Impressions is the engaging account of thirty years of travel and paleontological exploration by Philippe Taquet, one of the world's most noted paleontologists. Dr. Taquet takes the reader on a surprisingly far-flung tour ranging from the Provence countryside to the Niger desert, from the Brazilian bush to the Mongolian Steppes, and from the Laos jungle to the Moroccan mountains in search of dinosaur bones and what they have to tell us about a vanished world. With wry humor and lively anecdotes, Dr. Taquet retraces the history of paleontological research, along the way discussing the latest theories of dinosaur existence and extinction. Elegantly translated by Kevin Padian, Dinosaur Impressions provides a unique, thoughtful perspective not often encountered in American- and English-language works. This insightful, first-hand account of an exceptional career is also a travelogue par excellence that will enthrall enthusiasts and general readers alike. Philippe Taquet is the Director of the National Museum of Natural History in Paris and is a member of the French Academy of Sciences. Kevin Padian is a professor in the Department of Integrative Biology and Curator of the Museum of Paleontology at the University of California, Berkeley. He is also the editor of The Beginning of the Age of Dinosaurs (Cambridge, 1986) and The Encyclopedia of Dinosaurs (1997).

Taquet, Philippe

1998-09-01

56

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

57

Discovering Dinosaurs  

NSDL National Science Digital Library

This Encyclopedia Britannica website highlights the history and changes in thought surrounding dinosaurs since they were discovered. Beginning in the 1820s, this site explores the continued findings which have led to present-day theories regarding what dinosaurs were like, as well as what happened to them. Topics covered include dinosaur anatomy, physiology, characteristics of behavior, and the environments in which they lived. Each topic is discussed in a sequential order. This site contains classroom activities with a teacher's guide to help students explore and understand ideas about these creatures, using this website. The teacher's guide contains details about classroom management and assessment, as well as teaching tips. Links are provided for further information.

Allison-Bunnell, Steve

58

Lineage tracing of Pf4-Cre marks hematopoietic stem cells and their progeny.  

PubMed

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

Calaminus, Simon D J; Guitart, Amelie V; Guitart, Amelie; Sinclair, Amy; Schachtner, Hannah; Watson, Steve P; Holyoake, Tessa L; Kranc, Kamil R; Machesky, Laura M

2012-12-27

59

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

PubMed Central

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

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

2012-01-01

60

Dinosaurs and the Cretaceous Terrestrial Revolution  

PubMed Central

The observed diversity 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 long been debated whether dinosaurs were part of the Cretaceous Terrestrial Revolution (KTR), from 125–80?Myr ago, when flowering plants, herbivorous and social insects, squamates, birds and mammals all underwent a rapid expansion. Although an apparent explosion of dinosaur diversity occurred in the mid-Cretaceous, coinciding with the emergence of new groups (e.g. neoceratopsians, ankylosaurid ankylosaurs, hadrosaurids and pachycephalosaurs), results from the first quantitative study of diversification applied to a new supertree of dinosaurs show that this apparent burst in dinosaurian diversity in the last 18 Myr of the Cretaceous is a sampling artefact. Indeed, major diversification shifts occurred largely in the first one-third of the group's history. Despite the appearance of new clades of medium to large herbivores and carnivores later in dinosaur history, these new originations do not correspond to significant diversification shifts. Instead, the overall geometry of the Cretaceous part of the dinosaur tree does not depart from the null hypothesis of an equal rates model of lineage branching. Furthermore, we conclude that dinosaurs did not experience a progressive decline at the end of the Cretaceous, nor was their evolution driven directly by the KTR.

Lloyd, Graeme T; Davis, Katie E; Pisani, Davide; Tarver, James E; Ruta, Marcello; Sakamoto, Manabu; Hone, David W.E; Jennings, Rachel; Benton, Michael J

2008-01-01

61

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.

Tchorz, J S; Tome, M; Cloetta, 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

62

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.

63

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

PubMed

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(+) 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. PMID:22209845

Nishikawa, Masaki; Yanagawa, Naomi; Kojima, Nobuhiko; Yuri, Shunsuke; Hauser, Peter V; Jo, Oak D; Yanagawa, Norimoto

2011-12-22

64

Differential Adhesion Molecule Expression during Murine Embryonic Stem Cell Commitment to the Hematopoietic and Endothelial Lineages  

PubMed Central

Mouse embryonic stem cells (ESC) make cell fate decisions based on intrinsic and extrinsic factors. The decision of ESC to differentiate to multiple lineages in vitro occurs during the formation of embryoid bodies (EB) and is influenced by cell-environment interactions. However, molecular mechanisms underlying cell-environmental modulation of ESC fate decisions are incompletely understood. Since adhesion molecules (AM) influence proliferation and differentiation in developing and adult tissues, we hypothesized that specific AM interactions influence ESC commitment toward hematopoietic and endothelial lineages. Expression of AM in the adherens, tight and gap junction pathways in ESC subpopulations were quantified. E-cadherin (E-cad), Claudin-4 (Cldn4), Connexin-43 (Cx43), Zona Occludens-1 (ZO-1) and Zona Occludens-2 (ZO-2) transcript levels were differentially expressed during early stages of hematopoietic/endothelial commitment. Stable ESC lines were generated with reduced expression of E-cad, Cldn4, Cx43, ZO-1 and ZO-2 using shRNA technology. Functional and phenotypic consequences of modulating AM expression were assessed using hematopoietic colony forming assays, endothelial sprouting assays and surface protein expression. A decrease in E-cad, Cldn4, Cx43 and ZO-1 expression was associated with less commitment to the hematopoietic lineage and increased endothelial differentiation as evidenced by functional and phenotypic analysis. A reduction in ZO-2 expression did not influence endothelial differentiation, but decreased hematopoietic commitment two-fold. These data indicate that a subset of AM influence ESC decisions to commit to endothelial and hematopoietic lineages. Furthermore, differentially expressed AM may provide novel markers to delineate early stages of ESC commitment to hematopoietic/endothelial lineages.

Stankovich, Basha L.; Aguayo, Esmeralda; Barragan, Fatima; Sharma, Aniket; Pallavicini, Maria G.

2011-01-01

65

Make a Dinosaur  

NSDL National Science Digital Library

In this activity, learners explore the size and scale of dinosaurs. Learners listen to "Dinosaurs, Dinosaurs" by Byron Barton to understand some background information about dinosaurs. Then, learners use pipe cleaners or wire to create skeletal dinosaur models to scale based on reference drawings. As a group, learners then make a bar graph of the sizes of the dinosaurs. This activity is featured on page 19 of the "Dinosphere" unit of study for K-2 learners.

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

2004-01-01

66

Dinosaur Flesh and Bones  

NSDL National Science Digital Library

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

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

2004-01-01

67

Synaptically-Competent Neurons Derived from Canine Embryonic Stem Cells by Lineage Selection with EGF and Noggin  

Microsoft Academic Search

Pluripotent stem cell lines have been generated in several domestic animal species; however, these lines traditionally show poor self-renewal and differentiation. Using canine embryonic stem cell (cESC) lines previously shown to have sufficient self-renewal capacity and potency, we generated and compared canine neural stem cell (cNSC) lines derived by lineage selection with epidermal growth factor (EGF) or Noggin along the

Jared T. Wilcox; Jonathan K. Y. Lai; Esther Semple; Brigitte A. Brisson; Cathy Gartley; John N. Armstrong; Dean H. Betts

2011-01-01

68

Clonal and Lineage Analysis of Melanocyte Stem Cells and Their Progeny in the Zebrafish  

PubMed Central

The study of melanocyte biology in the zebrafish presents a highly tractable system for understanding fundamental principles of developmental biology. Melanocytes are visible in the transparent embryo and in the mature fish following metamorphosis, a physical transformation from the larval to adult form. While early developing larval melanocytes are direct derivatives of the neural crest, the remainder of melanocytes develop from unpigmented precursors, or melanocyte stem cells (MSCs). The Tol2 transposable element has facilitated the construction of stable transgenic lines that label melanocytes. In another application, integration of Tol2 constructs makes possible clonal analysis of melanocyte and MSC lineages. Drugs that block melanin synthesis, ablate melanocytes, and block establishment of MSC populations allow the interrogation of this model system for mechanisms of adult stem cell development and regulation.

Tryon, Robert C.; Johnson, Stephen L.

2013-01-01

69

Lineage-specific purification of neural stem/progenitor cells from differentiated mouse induced pluripotent stem cells.  

PubMed

Since induced pluripotent stem (iPS) cells have differentiation potential into all three germ layer-derived tissues, efficient purification of target cells is required in many fields of iPS research. One useful strategy is isolation of desired cells from differentiated iPS cells by lineage-specific expression of a drug-resistance gene, followed by drug selection. With this strategy, we purified neural stem/progenitor cells (NSCs), a good candidate source for regenerative therapy, from differentiated mouse iPS cells. We constructed a bicistronic expression vector simultaneously expressing blasticidin S resistance gene and DsRed under the control of tandem enhancer of a 257-base pair region of nestin second intron, an NSC-specific enhancer. This construct was efficiently inserted into the iPS genome by piggyBac transposon-mediated gene transfer, and the established subclone was differentiated into NSCs in the presence or absence of blasticidin S. Consequently, incubation with blasticidin S led to purification of NSCs from differentiated iPS cells. Our results suggest that a lineage-specific drug selection strategy is useful for purification of NSCs from differentiated iPS cells and that this strategy can be applied for the purification of other cell types. PMID:23694811

Maruyama, Masato; Yamashita, Yuji; Kase, Masahiko; Trifonov, Stefan; Sugimoto, Tetsuo

2013-05-21

70

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

PubMed Central

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.

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

2011-01-01

71

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

72

ERG is required for the differentiation of embryonic stem cells along the endothelial lineage  

PubMed Central

Background The molecular mechanisms that govern stem cell differentiation along the endothelial lineage remain largely unknown. Ets related gene (ERG) has recently been shown to participate in the transcriptional regulation of a number of endothelial specific genes including VE-cadherin (CD144), endoglin, and von Willebrand's Factor (vWF). The specific role of the ETS factor ERG during endothelial differentiation has not been evaluated. Results ERG expression and function were evaluated during the differentiation of embryonic stem cells into embryoid bodies (EB). The results of our study demonstrate that ERG is first expressed in a subpopulation of vascular endothelial growth factor receptor 2 (VEGF-R2) expressing cells that also express VE-cadherin. During ES cell differentiation, ERG expression remains restricted to cells of the endothelial lineage that eventually coalesce into primitive vascular structures within embryoid bodies. ERG also exhibits an endothelial cell (EC)-restricted pattern during embryogenesis. To further define the role of ERG during ES cell differentiation, we used a knockdown strategy to inhibit ERG expression. Delivery of three independent shRNA led to 70-85% reductions in ERG expression during ES cell differentiation compared to no change with control shRNA. ERG knockdown was associated with a marked reduction in the number of ECs, the expression of EC-restricted genes, and the formation of vascular structures. Conclusion The ETS factor ERG appears to be a critical regulator of EC differentiation.

2009-01-01

73

Progranulin expression in neural stem cells and their differentiated cell lineages: An immunocytochemical study.  

PubMed

Progranulin (PGRN) is a neurotrophic factor that regulates neurite outgrowth and enhances neuronal survival. The association between PGRN and neural stem cell (NSC) differentiation may aid in elucidating the underlying pathogenesis and potential treatments for neurodegenerative diseases. To investigate the association between PGRN and NSCs and their lineages, primary NSCs were prepared from the subventricular zone of neonatal Sprague Dawley pups (age, 1 day) and cultured in the neural stem cell medium. After 7 days in culture, NSCs aggregated into neurospheres and were maintained in the differential medium for 7 days following three passages. In addition, PGRN expression in neurospheres and differentiated cells (neurons, astrocytes and oligodendrocytes) were analyzed by immunocytochemistry. The PGRN expression and localization was also investigated in the brain tissues of neonatal rats (age, 1 and 7 days) by double immunofluorescence staining. The data indicated that PGRN was highly expressed in NSCs and their differentiated cell lineages in vitro. The results also demonstrated that PGRN was predominantly expressed in neurons and microglia in vivo, and marginally in NSCs, astrocytes and oligodendrocytes. The present study suggested that PGRN may be involved in the regulation of NSC differentiation. PMID:24002337

Lü, Lanhai; Luo, Li; Lu, Yinghong; Chen, Lizhi; Xu, Jie; Guo, Kaihua

2013-09-02

74

Transcription factor-induced lineage selection of stem-cell-derived neural progenitor cells.  

PubMed

The generation of specific types of neurons from stem cells offers important opportunities in regenerative medicine. However, future applications and proper verification of cell identities will require stringent ways to generate homogeneous neuronal cultures. Here we show that transcription factors like Lmx1a, Phox2b, Nkx2.2, and Olig2 can induce desired neuronal lineages from most expressing neural progenitor cells by a mechanism resembling developmental binary cell-fate switching. Such efficient selection of cell fate resulted in remarkable cellular enrichment that enabled global gene-expression validation of generated neurons and identification of previously unrecognized features in the studied cell lineages. Several sources of stem cells have a limited competence to differentiate into specific neuronal cell types; e.g., dopamine neurons. However, we show that the combination of factors that normally promote either regional or dedicated neuronal specification can overcome limitations in cellular competence and also promote efficient reprogramming in more remote neural contexts, including human neural progenitor cells. PMID:21624811

Panman, Lia; Andersson, Elisabet; Alekseenko, Zhanna; Hedlund, Eva; Kee, Nigel; Mong, Jamie; Uhde, Christopher W; Deng, Qiaolin; Sandberg, Rickard; Stanton, Lawrence W; Ericson, Johan; Perlmann, Thomas

2011-06-01

75

FGF4-dependent stem cells derived from rat blastocysts differentiate along the trophoblast lineage.  

PubMed

Differentiated trophoblast cell lineages arise from trophoblast stem (TS) cells. To date such a stem cell population has only been established in the mouse. The objective of this investigation was to establish TS cell populations from rat blastocysts. Blastocysts were cultured individually on a feeder layer of rat embryonic fibroblasts (REFs) in fibroblast growth factor-4 (FGF4) and heparin supplemented culture medium. Once cell colonies were established REF feeder layers could be replaced with REF conditioned medium. The blastocyst-derived cell lines, in either proliferative or differentiated states, did not express genes indicative of ICM-derived tissues. In the proliferative state the cells expressed established stem cell-associated markers of TS cells. Cells ceased proliferation and differentiated when FGF4, heparin, and REF conditioned medium were removed. Differentiation was characterized by a decline of stem cell-associated marker gene expression, the appearance of large polyploid cells (trophoblast giant cells), and the expression of trophoblast differentiation-associated genes. Collectively, the data indicate that the rat blastocyst-derived cell lines not only possess many features characteristic of mouse TS cells but also possess some distinct properties. These rat TS cell lines represent valuable new in vitro models for analyses of mechanisms controlling TS cell renewal and differentiation. PMID:21215265

Asanoma, Kazuo; Rumi, M A Karim; Kent, Lindsey N; Chakraborty, Damayanti; Renaud, Stephen J; Wake, Norio; Lee, Dong-Soo; Kubota, Kaiyu; Soares, Michael J

2011-01-05

76

Hypoxia-induced mixed-lineage leukemia 1 regulates glioma stem cell tumorigenic potential  

PubMed Central

Normal stem cells reside in functional niches critical for self-renewal and maintenance. Neural and hematopoietic stem cell niches, in particular, are characterized by restricted availability of oxygen and the resulting regulation by hypoxia-inducible factors (HIFs). Glioblastoma multiforme (GBM) is the most common malignant brain tumor and also contains high degrees of hypoxia. Heterogeneity within the neoplastic compartment has been well characterized in GBM and may be derived from genetic and epigenetic sources that co-evolve during malignant progression. Recent experimental evidence has supported the importance of hypoxia in glioma stem cell (GSC) niches. We hypothesized that HIFs require epigenetic-modifying proteins to promote tumor malignancy in GBM. Here we demonstrate that in GBM the histone methyltransferase mixed-lineage leukemia 1 (MLL1) is induced by hypoxia and enhances hypoxic responses. Loss of MLL1 reduces the expression of HIF transcripts and HIF2? protein. Targeting MLL1 by RNA interference inhibited the expression of HIF2? and target genes, including vascular endothelial growth factor (VEGF). GSCs expressed higher levels of MLL1 than matched non-stem tumor cells and depletion of MLL1 reduced GSC self-renewal, growth, and tumorigenicity. These studies have uncovered a novel mechanism mediating tumor hypoxic responses linking microenvironmental regulation of epigenetic-modifying proteins to cellular heterogeneity and provide rationale for the design of more sophisticated clinical approaches targeting epigenetic regulation.

Heddleston, J M; Wu, Q; Rivera, M; Minhas, S; Lathia, J D; Sloan, A E; Iliopoulos, O; Hjelmeland, A B; Rich, J N

2012-01-01

77

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

PubMed

Modeling the dynamics of cell population in tissues involving stem cell niches allows insight into the control mechanisms of the important wound healing process. It is well known that growth and divisions of stem cells are mainly repressed by niche cells, but can also be activated by signals released from wound. In addition, the proliferation and differentiation among three different types of cell: stem cells (SCs), intermediate progenitor cells (IPCs), and fully differentiated cells (FDCs) in stem cell lineage are under different activation and inhibition controls. We have developed a novel stochastic spatial dynamic model of cells. We can characterize not only overall cell population dynamics, but also details of temporal-spatial relationship of individual cells within a tissue. In our model, the shape, growth, and division of each cell are modeled using a realistic geometric model. Furthermore, the inhibited growth rate, proliferation and differentiation probabilities of individual cells are modeled through feedback loops controlled by secreted factors and wound signals from neighboring cells. With specific proliferation and differentiation probabilities, the actual division type that each cell will take is chosen by a Monte Carlo sampling process. With simulations, we study the effects of different strengths of wound signals to wound healing behaviors. We also study the correlations between chronic wound and cancerogenesis. PMID:24110994

Cao, Youfang; Naveed, Hammad; Liang, Claire; Liang, Jie

2013-07-01

78

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

2013-04-10

79

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

PubMed Central

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

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

2013-01-01

80

Regulation of adult human mesenchymal stem cells into osteogenic and chondrogenic lineages by different bioreactor systems.  

PubMed

The aim of this study was to examine the feasibility of expanding and regulating mesenchymal stem cells (MSCs) from isolated adult human bone marrow mononuclear cells, seeded on gelatin-hyaluronic acid biomatrices, and then to quantitatively compare the gene expression in three different culture systems. Individual and interactive effects of model system parameters on construct structure, function, and molecular properties were evaluated. The results showed that these adult human MSCs even at old age not only expressed primitive mesenchymal cell markers but also maintained a high level of colony-forming efficiency and were capable of differentiating into osteoblasts, chondrocytes, and adipocytes upon appropriate inductions. After 21 days of culture, we found that the osteoblastic and chondrocytic lineage gene expression were earlier and higher expressed in spinner flask bioreactor culture group when compared with the static culture and rotating wall vessel reactor culture. The osteogenic lineage proteins type I collagen, alkaline phosphatase, and osteocalcin were strongly stained in histological sections of spinner flask bioreactor culture, whereas these were less detected in the other two groups, especially in rotating wall vessel reactor culture. As for the markers associated with the chondrogenic lineage differentiation proteins, type II collagen was apparently expressed in spinner flask culture group, while the expression of proteoglycans (aggreacan, decorin) in three culture conditions took the lead of each other. We conclude that the spinner flask bioreactor with appropriate induction medium reported in this study may be used to rapidly expand adult MSCs and is likely to possess better induction results toward osteoblastic and chondrocytic lineages. PMID:18384159

Wang, Tzu-Wei; Wu, Hsi-Chin; Wang, Hsin-Yen; Lin, Feng-Huei; Sun, Jui-Sheng

2009-03-15

81

Feathered Dinosaurs  

NASA Astrophysics Data System (ADS)

Recent fossil discoveries from Early Cretaceous rocks of Liaoning Province, China, have provided a wealth of spectacular specimens. Included in these are the remains of several different kinds of small theropod dinosaurs, many of which are extremely closely related to modern birds. Unique preservation conditions allowed soft tissues of some of these specimens to be preserved. Many dinosaur specimens that preserve feathers and other types of integumentary coverings have been recovered. These fossils show a progression of integumentary types from simple fibers to feathers of modern aspect. The distribution of these features on the bodies of these animals is surprising in that some show large tail plumes, whereas others show the presence of wing-like structures on both fore and hind limbs. The phylogenetic distribution of feather types is highly congruent with models of feather evolution developed from developmental biology.

Norell, Mark A.; Xu, Xing

2005-01-01

82

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

83

Dinosaur biomechanics  

PubMed Central

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.

Alexander, R. McNeill

2006-01-01

84

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.

85

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.

86

Stem cell factor and granulocyte colony-stimulating factor promote neuronal lineage commitment of neural stem cells.  

PubMed

Stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF) were originally discovered as growth factors for hematopoietic stem cells (HSCs). It has been well defined that SCF and G-CSF contribute to regulation of lineage commitment for HSCs. However, little is known about whether SCF and G-CSF play roles in the determination and differentiation of neural stem cells (NSCs). Here we demonstrate the novel function of SCF and G-CSF in controlling cell cycle and cell fate determination of NSCs. We also observe that SCF and G-CSF promote neuronal differentiation and inhibit astroglial differentiation at the early stage of differentiation. In addition, our research data reveal that SCF in combination with G-CSF has a dual function in promoting cell cycle exit and directing neuronal fate commitment at the stage of NSC dividing. This coordination effect of SCF+G-CSF on cell cycle arrest and neuronal differentiation is through enhancing neurogenin 1 (Ngn1) activity. These findings extend current knowledge regarding the role of SCF and G-CSF in the regulation of neurogenesis and provide insights into the contribution of hematopoietic growth factors to brain development and remodeling. PMID:22099173

Piao, Chun-Shu; Li, Bin; Zhang, Li-Juan; Zhao, Li-Ru

2011-10-05

87

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.

88

X-ray Dinosaurs  

NSDL National Science Digital Library

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

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

2004-01-01

89

Topographic effect on human induced pluripotent stem cells differentiation towards neuronal lineage.  

PubMed

Pluripotent stem cells have the potential to develop into all cell types of the adult body. Besides chemical and mechanical cues, topographical effect of surfaces could also contribute to the development of new therapies in regenerative medicine. In the present study, we tested the effects of nanograting substrates with different widths (width:350 nm/2 ?m/5 ?m, height: 300 nm) on human induced pluripotent stem cells (hiPSCs), in particular regarding the commitment of stem cell differentiation to desired phenotypes. We found that nuclei of hiPSCs could align and elongate in the direction of the nano/microstructure, whereas they distributed randomly on flat surfaces. The contact guidance significantly increased when the cells were cultured on the surface with smaller pitch. Gene expression profiling by real-time PCR and immunostaining showed significant up-regulation of neuronal markers on nanostructured substrates either with solely topographical cues or combined with pre-neuronal induction. A width of 350 nm, in particular, induced highest neuronal marker expression. This study demonstrates the significance of topography, especially regarding the width of the structures, in directing differentiation of hiPSCs towards the neuronal lineage. Our study suggests the potential applications of surface topography in clinical regenerative medicine for nerve injury repair. PMID:23891397

Pan, Fei; Zhang, Miao; Wu, Guangming; Lai, Yuekun; Greber, Boris; Schöler, Hans R; Chi, Lifeng

2013-07-23

90

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.

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

2012-01-01

91

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

2012-06-18

92

Metakaryotic stem cell lineages in organogenesis of humans and other metazoans.  

PubMed

A non-eukaryotic, metakaryotic cell with large, open mouthed, bell shaped nuclei represents an important stem cell lineage in fetal/juvenile organogenesis in humans and rodents. each human bell shaped nucleus contains the diploid human DNA genome as tested by quantitative Feulgen DNA cytometry and fluorescent in situ hybridization with human pan-telomeric, pan-centromeric and chromosome specific probes. From weeks approximately 5-12 of human gestation the bell shaped nuclei are found in organ anlagen enclosed in sarcomeric tubular syncytia. Within syncytia bell shaped nuclear number increases binomially up to 16 or 32 nuclei; clusters of syncytia are regularly dispersed in organ anlagen. Syncytial bell shaped nuclei demonstrate two forms of symmetrical amitoses, facing or "kissing" bells and "stacking" bells resembling separation of two paper cups. Remarkably, DNA increase and nuclear fission occur coordinately. Importantly, syncytial bell shaped nuclei undergo asymmetrical amitoses creating organ specific ensembles of up to eight distinct closed nuclear forms, a characteristic required of a stem cell lineage. Closed nuclei emerging from bell shaped nuclei are eukaryotic as demonstrated by their subsequent increases by extra-syncytial mitoses populating the parenchyma of growing anlagen. From 9-14 weeks syncytia fragment forming single cells with bell shaped nuclei that continue to display both symmetrical and asymmetrical amitoses. These forms persist in the juvenile period and are specifically observed in bases of colonic crypts. Metakaryotic forms are found in organogenesis of humans, rats, mice and the plant Arabidopsis indicating an evolutionary origin prior to the divergence of plants and animals. PMID:20539738

Gostjeva, Elena V; Koledova, Vera; Tomita-Mitchell, Aoy; Mitchell, Michael; Goetsch, Mary A; Varmuza, Susannah; Fomina, Janna N; Darroudi, Firouz; Thilly, William G

2009-10-01

93

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.

94

Loss of discordant cells during micro-mass differentiation of embryonic stem cells into the chondrocyte lineage  

Microsoft Academic Search

Embryonic stem cells (ESCs) have attracted particular interest in regenerative medicine because of their unlimited self-renewal and multipotentiality for differentiation. Spontaneous differentiated ESCs display heterogeneous multipotent cell populations and generate teratomas in vivo, with process by which ESCs differentiate into specific lineages remaining unclear. In this study, we focused on the in vitro chondrocyte differentiation of ESCs through micro-mass without

A Yamashita; R Krawetz; D E Rancourt

2009-01-01

95

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

PubMed

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

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

2013-05-05

96

The locomotor musculature of basal ornithischian dinosaurs  

Microsoft Academic Search

The earliest ornithischian dinosaurs were small bipeds that possessed the derived, retroverted pubis that is synapomorphic for the clade. Their forelimbs were modified for grasping. Subsequently, ornithischians radiated into numerous body shapes and sizes. Three lineages independently evolved large size and quadrupedality, requiring profound changes to the osteology and myology of the locomotor apparatus. Using comparisons with extinct archosaurian outgroups,

Susannah C. R. Maidment; Paul M. Barrett

2011-01-01

97

Supplying clotting factors from hematopoietic stem cell-derived erythroid and megakaryocytic lineage cells.  

PubMed

Systemically distributed proteins such as clotting factors have been traditionally expressed from muscle or liver to achieve therapeutic, long-term expression. As long-lived cell capable of generating an abundant progeny, hematopoietic stem cells (HSCs) also merit consideration for this purpose. To be clinically relevant, this approach would require that hematopoietic cells be capable of expressing high levels of functional, secreted proteins, that the risk of insertional oncogenesis be minimized, and that sufficient stem cell engraftment be achieved following minimally invasive conditioning. Recent reports demonstrate the feasibility of expressing either factor IX (FIX) or factor VIII (FVIII) in erythroblasts and platelets using lineage-restricted vectors, resulting in effective treatments in mouse models of hemophilia. The erythroid system is especially powerful in providing high protein output, yielding FIX levels approaching 1 micro g/ml per vector copy in the plasma of long-term hematopoietic chimeras, a secretion level that vastly outperforms any other current mammalian constitutive or long-terminal repeat (LTR)-driven vector system. These early but promising studies raise the prospect of further developing these strategies for clinical investigation. PMID:19844194

Sadelain, Michel; Chang, Alex; Lisowski, Leszek

2009-10-20

98

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

PubMed Central

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

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

2013-01-01

99

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.

100

Dinosaur Tracks and Traces  

NASA Astrophysics Data System (ADS)

The study of fossilized dinosaur remains, vertebrate paleontology is a well established discipline, but the discovery and rediscovery of numerous and varied dinosaur footprints and nest sites has spurred a renaissance in the associated field of ichnological research. Dinosaur Tracks and Traces is the first book ever to be devoted to this subject, and it represents the work of seventy noted dinosaur ichnologists. Contributors address the history of science and the relevance of dinosaur ichnology to the interpretation of dinosaur behaviour, paleoecology, paleoenvironments, and evolution. Several new preservation, conservation, and documentation techniques are also presented. The book is richly illustrated and is intended for students and professionals in the areas of paleontology, vertebrate zoology, geology, and paleoenvironmental analysis. The historical aspects of the book and the many site descriptions also make Dinosaur Tracks and Traces appealing to amateur fossil collectors and dinosaur enthusiasts.

Gillette, David D.; Lockley, Martin G.

1991-02-01

101

What's New, Dinosaur?  

ERIC Educational Resources Information Center

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

Prime, Carol Spirkoff; Cox, Judy

1987-01-01

102

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

103

The Dinosaur Name Game  

NSDL National Science Digital Library

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

104

Limiting dilution analysis of the stem cells for T cell lineage  

SciTech Connect

Stem cell activities of bone marrow, spleen, thymus, and fetal liver cells for T cell lineage were studied comparatively by transferring the cells from these organs through i.v. or intrathymus (i.t.) route into right leg- and tail-shielded (L-T-shielded) and 900 R-irradiated recipient mice, which were able to survive without supplying hemopoietic stem cells. Cells from B10.Thy-1.1 (H-2b, Thy-1.1) mice were serially diluted and were transferred into L-T-shielded and irradiated C57BL/6 (H-2b, Thy-1.2) mice, and 21 days later the thymus cells of recipient mice were assayed for Thy-1.1+ cells by flow cytofluorometry. The percentage of recipient mice possessing donor-type T cells was plotted against the number of cells transferred, and the stem cell activity in each cell source was expressed as the 50% positive value, the number of donor cells required for generating donor-type T cells in the thymuses of 50% of recipient mice. In i.v. transfer experiments, the activity of bone marrow cells was similar to that of fetal liver cells, and about 100 times and nearly 1000 times higher than those of spleen cells and thymus cells, respectively. In i.t. transfer experiments, the number of cells required for generating donor-type T cells was much lower than that in i.v. transfer experiments, although the ratio in 50% positive values between i.v. and i.t. transfers differed among cell sources. In i.t. transfers, the 50% positive value of bone marrow cells was five times, 400 times, and 500 times higher than that of fetal liver cells, spleen cells, and thymus cells, respectively. Our previous finding that stem cells are enriched in the spleens of mice which were whole body-irradiated and marrow-reconstituted 7 days earlier was confirmed also by the present limiting dilution assay carried out in i.v. as well as i.t. transfers.

Katsura, Y.; Kina, T.; Amagai, T.; Tsubata, T.; Hirayoshi, K.; Takaoki, Y.; Sado, T.; Nishikawa, S.I.

1986-10-15

105

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

106

Thermoregulation in Dinosaurs  

Microsoft Academic Search

ANATOMICAL, physiological and ecological evidence has been assembled by Bakker1 in an attempt to demonstrate that dinosaurs were endotherms. But critical parts of this evidence are less than convincing and may be interpreted differently. Bakker suggests that dinosaurs were built for sustained locomotion at moderate speeds and infers from this that dinosaur energy metabolism was endotherm-like. But I consider it

R. A. Thulborn

1973-01-01

107

Blood-borne stem cells differentiate into vascular and cardiac lineages during normal development.  

PubMed

Recent investigations have indicated that hematopoietic stem cells (HSCs) have the potential to differentiate into multiple non-blood cell lineages and contribute to the cellular regeneration of various tissues and multiple organs. Most studies to date on HSC potential have examined the adult, focusing on their potential to repair tissue under pathological conditions (e.g., ischemic injury, organ failure). Comparatively little is known about the physiological role of HSCs in normal tissue homeostasis in the adult, and even less of their contribution to organogenesis during prenatal development. This study reports the contribution of blood-borne cells to various organ systems of the developing embryo using a quail-chick parabiosis model. Under these conditions, the developing circulatory systems fuse between ED6-ED8, resulting in free exchange of circulating cells. Cells of quail origin, identified by quail-specific antibodies at ED15, were found in numerous organs of the parabiotic chick embryo. Circulating cells contributed to developing vasculature, where they differentiated into endothelial, smooth muscle, and adventitial tissues. In the heart, differentiation of circulating cells into cardiomyocytes was demonstrated using double immunolabeling for QCPN and sarcomeric actin or myosin. These results were confirmed by intramyocardial injection of quail bone marrow cells that were found to express markers of myocytes, coronary smooth muscle, and epicardium. Experiments using lacZ-transgenic chick embryos for a second positive cellular marker showed that fusion between chick and quail cells was a rare event. These results suggest that during development, multipotent cells are present in the embryonic circulation and home into different organs where they undergo tissue-specific differentiation. Moreover, the demonstration that blood-borne cells contribute to the development of various organs lends credence to claims that hematopoietic stem cells have utility for treating diseased or damaged tissues in the adult. PMID:16522159

Zhang, Ning; Mustin, Deanna; Reardon, Wade; Almeida, Angela De; Mozdziak, Paul; Mrug, Michal; Eisenberg, Leonard M; Sedmera, David

2006-02-01

108

Phenotypic and functional characteristics of mesenchymal stem cells differentiated along a Schwann cell lineage.  

PubMed

We have investigated the phenotypic and bioassay characteristics of bone marrow mesenchymal stromal cells (MSCs) differentiated along a Schwann cell lineage using glial growth factor. Expression of the Schwann cell markers S100, P75, and GFAP was determined by immunocytochemical staining and Western blotting. The levels of the stem cell markers Stro-1 and alkaline phosphatase and the neural progenitor marker nestin were also examined throughout the differentiation process. The phenotypic properties of cells differentiated at different passages were also compared. In addition to a phenotypic characterization, the functional ability of differentiated MSCs has been investigated employing a co-culture bioassay with dissociated primary sensory neurons. Following differentiation, MSCs underwent morphological changes similar to those of cultured Schwann cells and stained positively for all three Schwann cell markers. Quantitative Western blot analysis showed that the levels of S100 and P75 protein were significantly elevated upon differentiation. Differentiated MSCs were also found to enhance neurite outgrowth in co-culture with sensory neurons to a level equivalent or superior to that produced by Schwann cells. These findings support the assertion that MSCs can be differentiated into cells that are Schwann cell-like in terms of both phenotype and function. PMID:16977603

Caddick, Jenny; Kingham, Paul J; Gardiner, Natalie J; Wiberg, Mikael; Terenghi, Giorgio

2006-12-01

109

The similarity between human embryonic stem cell-derived epithelial cells and ameloblast-lineage cells.  

PubMed

This study aimed to compare epithelial cells derived from human embryonic stem cells (hESCs) to human ameloblast-lineage cells (ALCs), as a way to determine their potential use as a cell source for ameloblast regeneration. Induced by various concentrations of bone morphogenetic protein 4 (BMP4), retinoic acid (RA) and lithium chloride (LiCl) for 7 days, hESCs adopted cobble-stone epithelial phenotype (hESC-derived epithelial cells (ES-ECs)) and expressed cytokeratin 14. Compared with ALCs and oral epithelial cells (OE), ES-ECs expressed amelogenesis-associated genes similar to ALCs. ES-ECs were compared with human fetal skin epithelium, human fetal oral buccal mucosal epithelial cells and human ALCs for their expression pattern of cytokeratins as well. ALCs had relatively high expression levels of cytokeratin 76, which was also found to be upregulated in ES-ECs. Based on the present study, with the similarity of gene expression with ALCs, ES-ECs are a promising potential cell source for regeneration, which are not available in erupted human teeth for regeneration of enamel. PMID:23538640

Zheng, Li-Wei; Linthicum, Logan; DenBesten, Pamela K; Zhang, Yan

2013-03-29

110

Life cycle and morphology of a cambrian stem-lineage loriciferan.  

PubMed

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

2013-08-09

111

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.

Peel, John S.; Stein, Martin; Kristensen, Reinhardt M?bjerg

2013-01-01

112

Supersize That Dinosaur  

NSDL National Science Digital Library

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

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

2004-01-01

113

Differentiated troy(+) chief cells act as reserve stem cells to generate all lineages of the stomach epithelium.  

PubMed

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

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

2013-10-10

114

CD15, CD24, and CD29 Define a Surface Biomarker Code for Neural Lineage Differentiation of Stem Cells  

PubMed Central

Identification and use of cell surface cluster of differentiation (CD) biomarkers have enabled much scientific and clinical progress. We identify a CD surface antigen code for the neural lineage based on combinatorial flow cytometric analysis of three distinct populations derived from human embryonic stem cells: (1) CD15+/CD29HI/CD24LO surface antigen expression defined neural stem cells; (2) CD15?/CD29HI/CD24LO revealed neural crest-like and mesenchymal phenotypes; and (3) CD15?/CD29LO/CD24HI selected neuroblasts and neurons. Fluorescence-activated cell sorting (FACS) for the CD15?/CD29LO/CD24HI profile reduced proliferative cell types in human embryonic stem cell differentiation. This eliminated tumor formation in vivo, resulting in pure neuronal grafts. In conclusion, combinatorial CD15/CD24/CD29 marker profiles define neural lineage development of neural stem cell, neural crest, and neuronal populations from human stem cells. We believe this set of biomarkers enables analysis and selection of neural cell types for developmental studies and pharmacological and therapeutic applications.

Pruszak, Jan; Ludwig, Wesley; Blak, Alexandra; Alavian, Kambiz; Isacson, Ole

2012-01-01

115

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

PubMed

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 cells (ESCs) and are induced concomitantly with 5hmC during reprogramming of fibroblasts to induced pluripotent stem cells. ESCs depleted of Tet1 by RNAi show diminished expression of the Nodal antagonist Lefty1 and display hyperactive Nodal signaling and skewed differentiation into the endoderm-mesoderm lineage in embryoid bodies in vitro. In Fgf4- and heparin-supplemented culture conditions, Tet1-depleted ESCs activate the trophoblast stem cell lineage determinant Elf5 and can colonize the placenta in midgestation embryo chimeras. Consistent with these findings, Tet1-depleted ESCs form aggressive hemorrhagic teratomas with increased endoderm, reduced neuroectoderm, and ectopic appearance of trophoblastic giant cells. Thus, 5hmC is an epigenetic modification associated with the pluripotent state, and Tet1 functions to regulate the lineage differentiation potential of ESCs. 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

2011-02-01

116

Influence of Discrete and Continuous Culture Conditions on Human Mesenchymal Stem Cell Lineage Choice in RGD Concentration Gradient Hydrogels.  

PubMed

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

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

2013-08-07

117

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

PubMed

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

Clarke, Andrew

2013-07-19

118

Mei-P26 regulates microRNAs and cell growth in the Drosophila ovarian stem cell lineage.  

PubMed

Drosophila neuroblasts and ovarian stem cells are well characterized models for stem cell biology. In both cell types, one daughter cell self-renews continuously while the other undergoes a limited number of divisions, stops to proliferate mitotically and differentiates. Whereas neuroblasts segregate the Trim-NHL (tripartite motif and Ncl-1, HT2A and Lin-41 domain)-containing protein Brain tumour (Brat) into one of the two daughter cells, ovarian stem cells are regulated by an extracellular signal from the surrounding stem cell niche. After division, one daughter cell looses niche contact. It undergoes 4 transit-amplifying divisions to form a cyst of 16 interconnected cells that reduce their rate of growth and stop to proliferate mitotically. Here we show that the Trim-NHL protein Mei-P26 (refs 7, 8) restricts growth and proliferation in the ovarian stem cell lineage. Mei-P26 expression is low in stem cells but is strongly induced in 16-cell cysts. In mei-P26 mutants, transit-amplifying cells are larger and proliferate indefinitely leading to the formation of an ovarian tumour. Like brat, mei-P26 regulates nucleolar size and can induce differentiation in Drosophila neuroblasts, suggesting that these genes act through the same pathway. We identify Argonaute-1, a component of the RISC complex, as a common binding partner of Brat and Mei-P26, and show that Mei-P26 acts by inhibiting the microRNA pathway. Mei-P26 and Brat have a similar domain composition that is also found in other tumour suppressors and might be a defining property of a new family of microRNA regulators that act specifically in stem cell lineages. PMID:18528333

Neumüller, Ralph A; Betschinger, Joerg; Fischer, Anja; Bushati, Natascha; Poernbacher, Ingrid; Mechtler, Karl; Cohen, Stephen M; Knoblich, Juergen A

2008-06-04

119

Deletion of the Scl +19 enhancer increases the blood stem cell compartment without affecting the formation of mature blood lineages.  

PubMed

The stem cell leukemia (Scl)/Tal1 gene is essential for normal blood and endothelial development, and is expressed in hematopoietic stem cells (HSCs), progenitors, erythroid, megakaryocytic, and mast cells. The Scl +19 enhancer is active in HSCs and progenitor cells, megakaryocytes, and mast cells, but not mature erythroid cells. Here we demonstrate that in vivo deletion of the Scl +19 enhancer (Scl(?19/?19)) results in viable mice with normal Scl expression in mature hematopoietic lineages. By contrast, Scl expression is reduced in the stem/progenitor compartment and flow cytometry analysis revealed that the HSC and megakaryocyte-erythroid progenitor populations are enlarged in Scl(?19/?19) mice. The increase in HSC numbers contributed to enhanced expansion in bone marrow transplantation assays, but did not affect multilineage repopulation or stress responses. These results affirm that the Scl +19 enhancer plays a key role in the development of hematopoietic stem/progenitor cells, but is not necessary for mature hematopoietic lineages. Moreover, active histone marks across the Scl locus were significantly reduced in Scl(?19/?19) fetal liver cells without major changes in steady-state messenger RNA levels, suggesting post-transcriptional compensation for loss of a regulatory element, a result that might be widely relevant given the frequent observation of mild phenotypes after deletion of regulatory elements. PMID:22401818

Spensberger, Dominik; Kotsopoulou, Ekaterini; Ferreira, Rita; Broccardo, Cyril; Scott, Linda M; Fourouclas, Nasios; Ottersbach, Katrin; Green, Anthony R; Göttgens, Berthold

2012-03-05

120

Deletion of the Scl +19 enhancer increases the blood stem cell compartment without affecting the formation of mature blood lineages  

PubMed Central

The stem cell leukemia (Scl)/Tal1 gene is essential for normal blood and endothelial development, and is expressed in hematopoietic stem cells (HSCs), progenitors, erythroid, megakaryocytic, and mast cells. The Scl +19 enhancer is active in HSCs and progenitor cells, megakaryocytes, and mast cells, but not mature erythroid cells. Here we demonstrate that in vivo deletion of the Scl +19 enhancer (Scl?19/?19) results in viable mice with normal Scl expression in mature hematopoietic lineages. By contrast, Scl expression is reduced in the stem/progenitor compartment and flow cytometry analysis revealed that the HSC and megakaryocyte-erythroid progenitor populations are enlarged in Scl?19/?19 mice. The increase in HSC numbers contributed to enhanced expansion in bone marrow transplantation assays, but did not affect multilineage repopulation or stress responses. These results affirm that the Scl +19 enhancer plays a key role in the development of hematopoietic stem/progenitor cells, but is not necessary for mature hematopoietic lineages. Moreover, active histone marks across the Scl locus were significantly reduced in Scl?19/?19 fetal liver cells without major changes in steady-state messenger RNA levels, suggesting post-transcriptional compensation for loss of a regulatory element, a result that might be widely relevant given the frequent observation of mild phenotypes after deletion of regulatory elements.

Spensberger, Dominik; Kotsopoulou, Ekaterini; Ferreira, Rita; Broccardo, Cyril; Scott, Linda M.; Fourouclas, Nasios; Ottersbach, Katrin; Green, Anthony R.; Gottgens, Berthold

2012-01-01

121

Control of three-dimensional substrate stiffness to manipulate mesenchymal stem cell fate toward neuronal or glial lineages.  

PubMed

The unlimited self-renewal and multipotency of stem cells provide great potential for applications in tissue engineering and regenerative medicine. The differentiation of stem cells can be induced by multiple factors including physical, chemical and biological cues. The fate of stem cells can be manipulated by deliberately controlling the interaction between stem cells and their microenvironment. The purpose of this study is to investigate the change in matrix stiffness under the influence of neurogenic differentiation of human mesenchymal stem cells (hMSCs). In this study, three-dimensional (3-D) porous scaffolds were synthesized by type I collagen (Col) and hyaluronic acid (HA). The elastic modulus of the 3-D substrates was modified by adjusting the concentration of 1-ethyl-3(3-dimethylaminopropyl) carbodiimide (EDC) as a crosslinking agent. The mechanical properties of Col-HA scaffolds were evaluated and the induction and characterization of hMSC differentiation toward neural lineages on substrates with different stiffnesses were studied. Using EDC of different concentrations for crosslinking, the stiffness of the matrices can be controlled in the range of 1-10 kPa for soft to stiff substrates, respectively. The results showed that MSCs were likely to differentiate into neuronal lineage in substrate at 1 kPa, while they transformed into glial cells in matrix at 10 kPa. The morphology and proliferation behavior of hMSCs responded to the different stiffnesses of substrates. Using this modifiable matrix, we can investigate the relationship between stem cell behavior and substrate mechanical properties in extracellular matrix-based biomimetic 3-D scaffolds. A substrate with controllable stiffness capable of inducing hMSCs specifically toward neuronal differentiation may be very useful as a tissue-engineered construct or substitute for delivering hMSCs into the brain and spinal cord. PMID:23079022

Her, Goh Jih; Wu, Hsi-Chin; Chen, Ming-Hong; Chen, Ming-Yi; Chang, Shun-Chih; Wang, Tzu-Wei

2012-10-16

122

Lineage tracing with Axin2 reveals distinct developmental and adult populations of Wnt/?-catenin-responsive neural stem cells  

PubMed Central

Since the discovery of neural stem cells in the mammalian brain, there has been significant interest in understanding their contribution to tissue homeostasis at both the cellular and molecular level. Wnt/?-catenin signaling is crucial for development of the central nervous system and has been implicated in stem cell maintenance in multiple tissues. Based on this, we hypothesized that the Wnt pathway likely controls neural stem cell maintenance and differentiation along the entire developmental continuum. To test this, we performed lineage tracing experiments using the recently developed tamoxifen-inducible Cre at Axin2 mouse strain to follow the developmental fate of Wnt/?-catenin–responsive cells in both the embryonic and postnatal mouse brain. From as early as embryonic day 8.5 onwards, Axin2+ cells can give rise to spatially and functionally restricted populations of adult neural stem cells in the subventricular zone. Similarly, progeny from Axin2+ cells labeled from E12.5 contribute to both the subventricular zone and the dentate gyrus of the hippocampus. Labeling in the postnatal brain, in turn, demonstrates the persistence of long-lived, Wnt/?-catenin–responsive stem cells in both of these sites. These results demonstrate the continued importance of Wnt/?-catenin signaling for neural stem and progenitor cell formation and function throughout developmental time.

Bowman, Angela N.; van Amerongen, Renee; Palmer, Theo D.; Nusse, Roeland

2013-01-01

123

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

124

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

125

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.

126

Create a Dinosaur Name  

NSDL National Science Digital Library

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

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

2004-01-01

127

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

128

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

PubMed

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

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

2013-05-23

129

Notch-Mediated Suppression of TSC2 Expression Regulates Cell Differentiation in the Drosophila Intestinal Stem Cell Lineage  

PubMed Central

Epithelial homeostasis in the posterior midgut of Drosophila is maintained by multipotent intestinal stem cells (ISCs). ISCs self-renew and produce enteroblasts (EBs) that differentiate into either enterocytes (ECs) or enteroendocrine cells (EEs) in response to differential Notch (N) activation. Various environmental and growth signals dynamically regulate ISC activity, but their integration with differentiation cues in the ISC lineage remains unclear. Here we identify Notch-mediated repression of Tuberous Sclerosis Complex 2 (TSC2) in EBs as a required step in the commitment of EBs into the EC fate. The TSC1/2 complex inhibits TOR signaling, acting as a tumor suppressor in vertebrates and regulating cell growth. We find that TSC2 is expressed highly in ISCs, where it maintains stem cell identity, and that N-mediated repression of TSC2 in EBs is required and sufficient to promote EC differentiation. Regulation of TSC/TOR activity by N signaling thus emerges as critical for maintenance and differentiation in somatic stem cell lineages.

Kapuria, Subir; Karpac, Jason; Biteau, Benoit; Hwangbo, DaeSung; Jasper, Heinrich

2012-01-01

130

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

PubMed

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

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

2012-07-20

131

Lineage Switching in Acute Leukemias: A Consequence of Stem Cell Plasticity?  

PubMed Central

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.

Dorantes-Acosta, Elisa; Pelayo, Rosana

2012-01-01

132

Nodal/Activin Signaling Predicts Human Pluripotent Stem Cell Lines Prone to Differentiate Toward the Hematopoietic Lineage  

PubMed Central

Lineage-specific differentiation potential varies among different human pluripotent stem cell (hPSC) lines, becoming therefore highly desirable to prospectively know which hPSC lines exhibit the highest differentiation potential for a certain lineage. We have compared the hematopoietic potential of 14 human embryonic stem cell (hESC)/induced pluripotent stem cell (iPSC) lines. The emergence of hemogenic progenitors, primitive and mature blood cells, and colony-forming unit (CFU) potential was analyzed at different time points. Significant differences in the propensity to differentiate toward blood were observed among hPSCs: some hPSCs exhibited good blood differentiation potential, whereas others barely displayed blood-differentiation capacity. Correlation studies revealed that the CFU potential robustly correlates with hemogenic progenitors and primitive but not mature blood cells. Developmental progression of mesoendodermal and hematopoietic transcription factors expression revealed no correlation with either hematopoietic initiation or maturation efficiency. Microarray studies showed distinct gene expression profile between hPSCs with good versus poor hematopoietic potential. Although neuroectoderm-associated genes were downregulated in hPSCs prone to hematopoietic differentiation many members of the Nodal/Activin signaling were upregulated, suggesting that this signaling predicts those hPSC lines with good blood-differentiation potential. The association between Nodal/Activin signaling and the hematopoietic differentiation potential was confirmed using loss- and gain-of-function functional assays. Our data reinforce the value of prospective comparative studies aimed at determining the lineage-specific differentiation potential among different hPSCs and indicate that Nodal/Activin signaling seems to predict those hPSC lines prone to hematopoietic specification.

Ramos-Mejia, Veronica; Melen, Gustavo J; Sanchez, Laura; Gutierrez-Aranda, Ivan; Ligero, Gertrudis; Cortes, Jose L; Real, Pedro J; Bueno, Clara; Menendez, Pablo

2010-01-01

133

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

134

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.

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

2011-01-01

135

Pluripotent lineage of CD133 stem cells isolated from human skin samples.  

PubMed

Skin stem cells are very important in cosmetics, pharmacological and regenerative medicine and burn cases. Foreskin samples surgically removed after circumcision from boys below 7 years were collected and primary epidermal cells were prepared by enzymatic and mechanical tituration method. Selecting CD133 (prominin-1) multipotent stem cell marker, enriched stem cells were analyzed by MACS using CD133 antibodies conjugated with magnetic beads. CD133 positive and negative cells with specific skin stem cells markers like - CD34 (Universal stem cells marker), CD29 (integrin beta-1) and CD49f (integrin alpha-6) immunophenotypes were screened and sorted in flowcytometer. Further the expression of four embryonic genes or transcription factors of pluripotent stem cells were analyzed for pluripotent character of sorted cells. It was found that skin stem cell markers associated with CD133 cells, differentially expressed CD34, CD29 and CD49f immunophenotyes on both positive and negative CD133 cells in FACS analysis. The embryonic stem cell markers (induced pluripotent stem cell markers) like Oct4, SOX2, Notch-2 and K19 genes were expressed in CD133 positive epidermal cells. It is therefore evident that foreskin derived epidermal stem cells showed pluripotent or multipotent nature. This finding opens up avenues for new uses of these stem cells for direct cell seeding in wound healing, surgical suturing and drug screening. PMID:23923603

Balaji, Avvari Bhaskara; Jamil, Kaiser; Ram, Gangaraju Maruthi; Raju, G Suryanarayana

2013-02-01

136

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

PubMed Central

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

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

2012-01-01

137

Pyrvinium, a potent small molecule Wnt inhibitor, increases engraftment and inhibits lineage commitment of mesenchymal stem cells (MSCs).  

PubMed

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

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

2012-02-14

138

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

139

Digging into Dinosaurs.  

ERIC Educational Resources Information Center

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

Braus, Judy, Ed.

1989-01-01

140

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.

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

2012-01-01

141

Mouse lysocardiolipin acyltransferase controls the development of hematopoietic and endothelial lineages during in vitro embryonic stem-cell differentiation  

PubMed Central

The blast colony-forming cell (BL-CFC) was identified as an equivalent to the hemangioblast during in vitro embryonic stem (ES) cell differentiation. However, the molecular mechanisms underlying the generation of the BL-CFC remain largely unknown. Here we report the isolation of mouse lysocardiolipin acyltransferase (Lycat) based on homology to zebrafish lycat, a candidate gene for the cloche locus. Mouse Lycat is expressed in hematopoietic organs and is enriched in the Lin?C-Kit+Sca-1+ hematopoietic stem cells in bone marrow and in the Flk1+/hCD4+(Scl+) hemangioblast population in embryoid bodies. The forced Lycat transgene leads to increased messenger RNA expression of hematopoietic and endothelial genes as well as increased blast colonies and their progenies, endothelial and hematopoietic lineages. The Lycat small interfering RNA transgene leads to a decrease expression of hematopoietic and endothelial genes. An unbiased genomewide microarray analysis further substantiates that the forced Lycat transgene specifically up-regulates a set of genes related to hemangioblasts and hematopoietic and endothelial lineages. Therefore, mouse Lycat plays an important role in the early specification of hematopoietic and endothelial cells, probably acting at the level of the hemangioblast.

Wang, Chengyan; Faloon, Patrick W.; Tan, Zhijia; Lv, Yaxin; Zhang, Pengbo; Ge, Yu; Deng, Hongkui

2007-01-01

142

Induction of Multipotential Hematopoietic Progenitors from Human Pluripotent Stem Cells via Respecification of Lineage-Restricted Precursors.  

PubMed

Human pluripotent stem cells (hPSCs) represent a promising source of patient-specific cells for disease modeling, drug screens, and cellular therapies. However, the inability to derive engraftable human hematopoietic stem and progenitor cells (HSPCs) has limited their characterization to in vitro assays. We report a strategy to respecify lineage-restricted CD34(+)CD45(+) myeloid precursors derived from hPSCs into multilineage progenitors that can be expanded in vitro and engrafted in vivo. HOXA9, ERG, and RORA conferred self-renewal and multilineage potential in vitro and maintained primitive CD34(+)CD38(-) cells. Screening cells via transplantation revealed that two additional factors, SOX4 and MYB, conferred engraftment. Progenitors specified with all five factors gave rise to reproducible short-term engraftment with myeloid and erythroid lineages. Erythroid precursors underwent hemoglobin switching in vivo, silencing embryonic and activating adult globin expression. Our combinatorial screening approach establishes a strategy for obtaining transcription-factor-mediated engraftment of blood progenitors from human pluripotent cells. PMID:24094326

Doulatov, Sergei; Vo, Linda T; Chou, Stephanie S; Kim, Peter G; Arora, Natasha; Li, Hu; Hadland, Brandon K; Bernstein, Irwin D; Collins, James J; Zon, Leonard I; Daley, George Q

2013-10-01

143

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

2013-10-04

144

Amniotic fluid stem cells morph into a cardiovascular lineage: analysis of a chemically induced cardiac and vascular commitment  

PubMed Central

Mouse embryonic stem cells were previously observed along with mesenchymal stem cells from different sources, after being treated with a mixed ester of hyaluronan with butyric and retinoic acids, to show a significant increase in the yield of cardiogenic and vascular differentiated elements. The aim of the present study was to determine if stem cells derived from primitive fetal cells present in human amniotic fluid (hAFSCs) and cultured in the presence of a mixture of hyaluronic (HA), butyric (BU), and retinoic (RA) acids show a higher yield of differentiation toward the cardiovascular phenotype as compared with untreated cells. During the differentiation process elicited by exposure to HA + BU + RA, genes controlling pluripotency and plasticity of stem cells, such as Sox2, Nanog, and Oct4, were significantly downregulated at the transcriptional level. At this point, a significant increase in expression of genes controlling the appearance of cardiogenic and vascular lineages in HA + BU + RA-treated cells was observed. The protein expression levels typical of cardiac and vascular phenotypes, evaluated by Western blotting, immunofluorescence, and flow cytometry, were higher in hAFSCs cultured in the presence of HA + BU + RA, as compared with untreated control cells. Appearance of the cardiac phenotype was further inferred by ultrastructural analysis using transmission and scanning electron microscopy. These results demonstrate that a mixture of HA + BU + RA significantly increased the yield of elements committed toward cardiac and vascular phenotypes, confirming what we have previously observed in other cellular types.

Maioli, Margherita; Contini, Giovanni; Santaniello, Sara; Bandiera, Pasquale; Pigliaru, Gianfranco; Sanna, Raimonda; Rinaldi, Salvatore; Delitala, Alessandro P; Montella, Andrea; Bagella, Luigi; Ventura, Carlo

2013-01-01

145

Amniotic fluid stem cells morph into a cardiovascular lineage: analysis of a chemically induced cardiac and vascular commitment.  

PubMed

Mouse embryonic stem cells were previously observed along with mesenchymal stem cells from different sources, after being treated with a mixed ester of hyaluronan with butyric and retinoic acids, to show a significant increase in the yield of cardiogenic and vascular differentiated elements. The aim of the present study was to determine if stem cells derived from primitive fetal cells present in human amniotic fluid (hAFSCs) and cultured in the presence of a mixture of hyaluronic (HA), butyric (BU), and retinoic (RA) acids show a higher yield of differentiation toward the cardiovascular phenotype as compared with untreated cells. During the differentiation process elicited by exposure to HA + BU + RA, genes controlling pluripotency and plasticity of stem cells, such as Sox2, Nanog, and Oct4, were significantly downregulated at the transcriptional level. At this point, a significant increase in expression of genes controlling the appearance of cardiogenic and vascular lineages in HA + BU + RA-treated cells was observed. The protein expression levels typical of cardiac and vascular phenotypes, evaluated by Western blotting, immunofluorescence, and flow cytometry, were higher in hAFSCs cultured in the presence of HA + BU + RA, as compared with untreated control cells. Appearance of the cardiac phenotype was further inferred by ultrastructural analysis using transmission and scanning electron microscopy. These results demonstrate that a mixture of HA + BU + RA significantly increased the yield of elements committed toward cardiac and vascular phenotypes, confirming what we have previously observed in other cellular types. PMID:24101862

Maioli, Margherita; Contini, Giovanni; Santaniello, Sara; Bandiera, Pasquale; Pigliaru, Gianfranco; Sanna, Raimonda; Rinaldi, Salvatore; Delitala, Alessandro P; Montella, Andrea; Bagella, Luigi; Ventura, Carlo

2013-09-27

146

Differentiation of human umbilical cord blood CD133+ stem cells towards myelo–monocytic lineage  

Microsoft Academic Search

Background: Characterisation of stem cells by flow cytometry, their expansion and differentiation are presently of major interest for cell engineering as the basis of a therapeutic concept for transplantation. Haematopoietic stem cells (HSC) express CD34, the adhesion structure which binds 2L-selectin, CD117, a receptor for stem cell factor (SCF; c-kit ligand), and CD133, a transmembrane protein belonging to the family

Katharina Ruzicka; Branka Grskovic; Vladimir Pavlovic; Durdi Qujeq; Alireza Karimi; Mathias M. Mueller

2004-01-01

147

Directed differentiation into neural lineages and therapeutic potential of porcine embryonic stem cells in rat Parkinson's disease model.  

PubMed

This study was conducted to direct porcine embryonic stem (pES) cells differentiating into neural lineages and to investigate therapeutic potential of GFP-expressing pES (pES/GFP(+)) in the rat model of Parkinson's disease (PD). Directed differentiation of pES into neural lineages was induced by suspension culture in medium containing RA, SHH, and FGF combinations without going through embryoid body formation. A high yield of nestin-expressing neural precursors was found in all treatments on day 2 after the 12-day induction. On day 6 after replating, more than 86.2 and 83.4% of the differentiated cells stained positively for NFL and MAP2, respectively. The expression of TH, ChAT, and GABA specific markers were also observed in these NFL-positive neural cells. The undifferentiated pES/GFP(+) cells and their neuronal differentiation derivatives were transplanted into the Sprague-Dawley (SD) rat's brain, and their survival and development was determined by using live animal fluorescence optical imaging system every 15 days. The results showed that fluorescent signals from the injection site of SD rats' brain could be detected through the experimental period of 3 months. The level of fluorescent signal detected in the treatment group was twofold that of the control group. The results of behavior analysis showed that PD rats exhibited stably decreased asymmetric rotations after transplantation with pES/GFP(+)-derived D18 neuronal progenitors. The dopaminergic differentiation of grafted cells in the brain was further confirmed by immunohistochemical staining with anti-TH, anti-DA, and anti-DAT antibodies. These results suggested that the differentiation approach we developed would direct pES cells to differentiate into neural lineages and benefit the development of novel therapeutics involving stem cell transplantation. PMID:20698783

Yang, Jenn-Rong; Liao, Chia-Hsin; Pang, Cheng-Yoong; Huang, Lynn Ling-Huei; Lin, Yu-Ting; Chen, Yi-Ling; Shiue, Yow-Ling; Chen, Lih-Ren

2010-08-01

148

Wnt signaling regulates the lineage differentiation potential of mouse embryonic stem cells through Tcf3 down-regulation.  

PubMed

Canonical Wnt signaling plays a rate-limiting role in regulating self-renewal and differentiation in mouse embryonic stem cells (ESCs). We have previously shown that mutation in the Apc (adenomatous polyposis coli) tumor suppressor gene constitutively activates Wnt signaling in ESCs and inhibits their capacity to differentiate towards ecto-, meso-, and endodermal lineages. However, the underlying molecular and cellular mechanisms through which Wnt regulates lineage differentiation in mouse ESCs remain to date largely unknown. To this aim, we have derived and studied the gene expression profiles of several Apc-mutant ESC lines encoding for different levels of Wnt signaling activation. We found that down-regulation of Tcf3, a member of the Tcf/Lef family and a key player in the control of self-renewal and pluripotency, represents a specific and primary response to Wnt activation in ESCs. Accordingly, rescuing Tcf3 expression partially restored the neural defects observed in Apc-mutant ESCs, suggesting that Tcf3 down-regulation is a necessary step towards Wnt-mediated suppression of neural differentiation. We found that Tcf3 down-regulation in the context of constitutively active Wnt signaling does not result from promoter DNA methylation but is likely to be caused by a plethora of mechanisms at both the RNA and protein level as shown by the observed decrease in activating histone marks (H3K4me3 and H3-acetylation) and the upregulation of miR-211, a novel Wnt-regulated microRNA that targets Tcf3 and attenuates early neural differentiation in mouse ESCs. Our data show for the first time that Wnt signaling down-regulates Tcf3 expression, possibly at both the transcriptional and post-transcriptional levels, and thus highlight a novel mechanism through which Wnt signaling inhibits neuro-ectodermal lineage differentiation in mouse embryonic stem cells. PMID:23658527

Atlasi, Yaser; Noori, Rubina; Gaspar, Claudia; Franken, Patrick; Sacchetti, Andrea; Rafati, Haleh; Mahmoudi, Tokameh; Decraene, Charles; Calin, George A; Merrill, Bradley J; Fodde, Riccardo

2013-05-02

149

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

PubMed Central

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

Wings, Oliver; Sander, P. Martin

2006-01-01

150

Are Birds Really Dinosaurs?  

NSDL National Science Digital Library

Evidence presented on this site is overwhelmingly in favor of birds being the descendants of a maniraptoran dinosaur, probably something similar (but not identical) to a small dromaeosaur. Dr. Jacques Gauthier created the first well-accepted, detailed phylogeny of the diapsids. His work provided strong, compelling support for the theory that birds are theropod dinosaurs. The development of the theory is traced and a list of twenty major skeletal characteristics the first birds shared with many coelurosaurian dinosaurs is included. The site contains many active links for further study.

Hutchinson, John

151

Ablation of Dido3 compromises lineage commitment of stem cells in vitro and during early embryonic development  

PubMed Central

The death inducer obliterator (Dido) locus encodes three protein isoforms, of which Dido3 is the largest and most broadly expressed. Dido3 is a nuclear protein that forms part of the spindle assembly checkpoint (SAC) and is necessary for correct chromosome segregation in somatic and germ cells. Here we report that specific ablation of Dido3 function in mice causes lethal developmental defects at the onset of gastrulation. Although these defects are associated with centrosome amplification, spindle malformation and a DNA damage response, we provide evidence that embryonic lethality of the Dido3 mutation cannot be explained by its impact on chromosome segregation alone. We show that loss of Dido3 expression compromises differentiation of embryonic stem cells in vitro and of epiblast cells in vivo, resulting in early embryonic death at around day 8.5 of gestation. Close analysis of Dido3 mutant embryoid bodies indicates that ablation of Dido3, rather than producing a generalized differentiation blockade, delays the onset of lineage commitment at the primitive endoderm specification stage. The dual role of Dido3 in chromosome segregation and stem cell differentiation supports the implication of SAC components in stem cell fate decisions.

Futterer, A; Raya, A; Llorente, M; Izpisua-Belmonte, J C; de la Pompa, J L; Klatt, P; Martinez-A, C

2012-01-01

152

PTEN maintains haematopoietic stem cells and acts in lineage choice and leukaemia prevention  

Microsoft Academic Search

Haematopoietic stem cells (HSCs) must achieve a balance between quiescence and activation that fulfils immediate demands for haematopoiesis without compromising long-term stem cell maintenance, yet little is known about the molecular events governing this balance. Phosphatase and tensin homologue (PTEN) functions as a negative regulator of the phosphatidylinositol-3-OH kinase (PI(3)K)-Akt pathway, which has crucial roles in cell proliferation, survival, differentiation

Jiwang Zhang; Justin C. Grindley; Tong Yin; Sachintha Jayasinghe; Xi C. He; Jason T. Ross; Jeffrey S. Haug; Dawn Rupp; Kimberly S. Porter-Westpfahl; Leanne M. Wiedemann; Hong Wu; Linheng Li

2006-01-01

153

In vitro immunogenicity of undifferentiated pluripotent stem cells (PSC) and derived lineages  

Microsoft Academic Search

The observation that embryonic stem cells (ESCs) expressed reduced levels of major histocompatibility (MHC) class I genes,\\u000a no MHC class II or costimulatory molecules suggested early on that pluripotent stem cells (PSCs) could be “immune-privileged”\\u000a and were unable to induce immune reactions. However, soon it became apparent that in some instances, ESCs were recognized\\u000a by immune cells but still could

Suzanne Kadereit; Alan Trounson

154

Synthetic nanostructures inducing differentiation of human mesenchymal stem cells into neuronal lineage  

Microsoft Academic Search

Human mesenchymal stem cells (hMSCs) have been shown to trans-differentiate into neuronal-like cells by culture in neuronal induction media, although the mechanism is not well understood. Topography can also influence cellular responses including enhanced differentiation of progenitor cells. As extracellular matrix (ECM) in vivo comprises topography in the nanoscale, we hypothesize that nanotopography could influence stem cell differentiation into specific

Evelyn K. F. Yim; Stella W. Pang; Kam W.. Leong

2007-01-01

155

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.

156

The Dinosaur Body  

NSDL National Science Digital Library

In this activity, students will recognize that body design affects balance by building models of dinosaur body types, using straws and marshmallows. There is background information, procedure, and a lab investigation with questions in this activity.

Wixom, Jo

157

Dinosaur Count and Sort  

NSDL National Science Digital Library

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

Omsi

2004-01-01

158

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.

159

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

160

How Big Were Dinosaurs?  

NSDL National Science Digital Library

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

161

Tbx5 overexpression favors a first heart field lineage in murine embryonic stem cells and in Xenopus laevis embryos.  

PubMed

The T-box transcription factor Tbx5 is involved in several developmental processes including cardiogenesis. Early steps of cardiac development are characterised by the formation of two cardiogenic lineages, the first (FHF) and the second heart field (SHF) lineage, which arise from a common cardiac progenitor cell population. To further investigate the function of Tbx5 during cardiogenesis, we generated a murine embryonic stem cell line constitutively overexpressing Tbx5. Differentiation of these cells is characterised by an earlier and increased appearance of contracting cardiomyocytes that beat with a higher frequency than control cells. In semi-quantitative and quantitative RT-PCR analyses, we observed an up-regulation of cardiac marker genes such as Troponin T, endogenous Tbx5, and Nkx2.5 and a down-regulation of others like BMP4 and Hand2. Similar data were gained in Xenopus laevis arguing for a conserved function of Tbx5. Furthermore, markers of the conduction system and atrial cardiomyocytes were increased. PMID:22072574

Herrmann, Franziska; Bundschu, Karin; Kühl, Susanne J; Kühl, Michael

2011-12-01

162

TSC1/2 regulates intestinal stem cell maintenance and lineage differentiation through Rheb-TORC1-S6K but independently of nutritional status or Notch regulation.  

PubMed

Tubular sclerosis complex gene products TSC1 and TSC2 have evolutionarily conserved roles in cell growth from Drosophila to mammals. Here we reveal important roles for TSC1/2 in regulating intestinal stem cell (ISC) maintenance and differentiation of the enteroendocrine cell lineage in the Drosophila midgut. Loss of either the Tsc1 or Tsc2 gene in ISCs causes rapid ISC loss through TORC1 hyperactivation, because ISCs can be efficiently rescued by mutation of S6k or by rapamycin treatment. In addition, overexpression of Rheb, which triggers TORC1 activation, recapitulates the phenotype caused by TSC1/2 disruption. Genetic studies suggest that TSC1/2 maintains ISCs independently of nutritional status or Notch regulation, probably by inhibiting cell delamination. We show that Tsc1/Tsc2 mutant ISCs can efficiently produce enterocytes but not enteroendocrine cells, and this altered differentiation potential is also caused by hyperactivation of TORC1. Reduced TORC1-S6K signaling by mutation of S6k, however, has no effect on ISC maintenance or cell lineage differentiation. Our studies demonstrate that hyperactivation of TORC1 following the loss of TSC1/2 is detrimental to stem cell maintenance and multiple lineage differentiation in the Drosophila ISC lineage, a mechanism that could be conserved in other stem cell lineages, including that in humans. PMID:23843608

Quan, Zhenghui; Sun, Pei; Lin, Guonan; Xi, Rongwen

2013-07-10

163

Perivascular Human Endometrial Mesenchymal Stem Cells Express Pathways Relevant to Self-Renewal, Lineage Specification, and Functional Phenotype1  

PubMed Central

ABSTRACT Human endometrium regenerates on a cyclic basis from candidate stem/progenitors whose genetic programs are yet to be determined. A subpopulation of endometrial stromal cells, displaying key properties of mesenchymal stem cells (MSCs), has been characterized. The endometrial MSC (eMSC) is likely the precursor of the endometrial stromal fibroblast. The goal of this study was to determine the transcriptome and signaling pathways in the eMSC to understand its functional phenotype. Endometrial stromal cells from oocyte donors (n = 20) and patients undergoing benign gynecologic surgery (n = 7) were fluorescence-activated cell sorted into MCAM (CD146)+/PDGFRB+ (eMSC), MCAM (CD146)?/PDGFRB+ (fibroblast), and MCAM (CD146)+/PDGFRB? (endothelial) populations. The eMSC population contained clonogenic cells with a mesenchymal phenotype differentiating into adipocytes when cultured in adipogenic medium. Gene expression profiling using Affymetrix Human Gene 1.0 ST arrays revealed 762 and 1518 significantly differentially expressed genes in eMSCs vs. stromal fibroblasts and eMSCs vs. endothelial cells, respectively. By principal component and hierarchical clustering analyses, eMSCs clustered with fibroblasts and distinctly from endothelial cells. Endometrial MSCs expressed pericyte markers and were localized by immunofluorescence to the perivascular space of endometrial small vessels. Endometrial MSCs also expressed genes involved in angiogenesis/vasculogenesis, steroid hormone/hypoxia responses, inflammation, immunomodulation, cell communication, and proteolysis/inhibition, and exhibited increased Notch, TGFB, IGF, Hedgehog, and G-protein-coupled receptor signaling pathways, characteristic of adult tissue MSC self-renewal and multipotency. Overall, the data support the eMSC as a clonogenic, multipotent pericyte that displays pathways of self-renewal and lineage specification, the potential to respond to conditions during endometrial desquamation and regeneration, and a genetic program predictive of its differentiated lineage, the stromal fibroblast.

Spitzer, Trimble L.B.; Rojas, Angela; Zelenko, Zara; Aghajanova, Lusine; Erikson, David W.; Barragan, Fatima; Meyer, Michelle; Tamaresis, John S.; Hamilton, Amy E.; Irwin, Juan C.; Giudice, Linda C.

2011-01-01

164

Dinosaurs: Fuzzy origins for feathers  

Microsoft Academic Search

Cretaceous fossil deposits in China are famous for their feathered dinosaurs. But the surprising discovery of a herbivorous dinosaur with a filamentous coat raises fresh questions about the evolution of feathers.

Lawrence M. Witmer

2009-01-01

165

“Rainbow” Reporters for Multispectral Marking and Lineage Analysis of Hematopoietic Stem Cells  

Microsoft Academic Search

Hematologic diseases potentially benefiting from gene-based therapies involving hematopoietic stem cells (HSCs) include hereditary hemoglobinopathies, immunodeficiency syndromes, and congenital bleeding disorders such as hemophilia A, as well as acquired diseases like AIDS. Successful treatment of these blood diseases with gene-modified HSCs requires high effi- ciency gene delivery to the target cell population and persistence of transgene expression following differen- tiation.

Teresa S. Hawley; William G. Telford; ROBERT G. HAWLEYb

2001-01-01

166

Stem Rust Resistance in Triticum monococcum Germplasm of the Ug99 Lineage  

Technology Transfer Automated Retrieval System (TEKTRAN)

Wheat stem rust, caused by Puccinia graminis f. sp. tritici, has been effectively controlled through the use of genetic resistance. The recently identified race TTKSK (Ug99) possesses virulence to many resistance genes that have been used in wheat breeding worldwide. One strategy to aid breeders in ...

167

IGF-1 Instructs Multipotent Adult CNS Neural Stem Cells to an Oligodendroglial Lineage.  

National Technical Information Service (NTIS)

Adult neural stem cells differentiate into neurons, astrocytes, and oligodendrocytes in the mammalian CNS, but the molecular mechanisms that control their differentiation are not yet well understood. Insulin-like growth factor-I (IGF-I) can promote the di...

F. H. Gage J. Hsieh

2004-01-01

168

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

169

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

170

Synthetic nanostructures inducing differentiation of human mesenchymal stem cells into neuronal lineage  

SciTech Connect

Human mesenchymal stem cells (hMSCs) have been shown to trans-differentiate into neuronal-like cells by culture in neuronal induction media, although the mechanism is not well understood. Topography can also influence cellular responses including enhanced differentiation of progenitor cells. As extracellular matrix (ECM) in vivo comprises topography in the nanoscale, we hypothesize that nanotopography could influence stem cell differentiation into specific non-default pathways, such as transdifferentiation of hMSCs. Differentiation and proliferation of hMSCs were studied on nanogratings of 350 nm width. Cytoskeleton and nuclei of hMSCs were aligned and elongated along the nanogratings. Gene profiling and immunostaining showed significant up-regulation of neuronal markers such as microtubule-associated protein 2 (MAP2) compared to unpatterned and micropatterned controls. The combination of nanotopography and biochemical cues such as retinoic acid further enhanced the up-regulation of neuronal marker expressions, but nanotopography showed a stronger effect compared to retinoic acid alone on unpatterned surface. This study demonstrated the significance of nanotopography in directing differentiation of adult stem cells.

Yim, Evelyn K.F. [Department of Biomedical Engineering, Duke University, Durham, NC 27708 (United States); Pang, Stella W. [Solid State Electronics Laboratory, Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, MI 48109 (United States); Leong, Kam W. [Department of Biomedical Engineering, Duke University, Durham, NC 27708 (United States)]. E-mail: kam.leong@duke.edu

2007-05-15

171

Modeling spatial population dynamics of stem cell lineage in tissue growth  

PubMed Central

Understanding the dynamics of cell population allows insight into the control mechanism of the growth and development of mammalian tissues. It is well known that the proliferation and differentiation among stem cells (SCs), intermediate progenitor cells (IPCs), and fully differentiated cells (FDCs) are under different activation and inhibition controls. Secreted factors in negative feedback loops have already been identified as major elements in regulating the numbers of different cell types and in maintaining the equilibrium of cell populations. We have developed a novel spatial dynamic model of cells. We can characterize not only overall cell population dynamics, but also details of temporal-spatial relationship of individual cells within a tissue. In our model, the shape, growth, and division of each cell are modeled using a realistic geometric model. Furthermore, the inhibited growth rate, proliferation and differentiation probabilities of individual cells are modeled through feedback loops controlled by secreted factors of neighboring cells within a proper diffusion radius. With specific proliferation and differentiation probabilities, the actual division type that each cell will take is chosen by a Monte Carlo sampling process. With simulations we found that with proper strengths of inhibitions to growth and stem cell divisions, the whole tissue is capable of achieving a homeostatic size control. We discuss our findings on control mechanisms of the stability of the tissue development. Our model can be applied to study broad issues on tissue development and pattern formation in stem cell and cancer research.

Cao, Youfang; Liang, Claire; Naveed, Hammad; Li, Yingzi; Chen, Meng; Nie, Qing

2013-01-01

172

Modeling spatial population dynamics of stem cell lineage in tissue growth.  

PubMed

Understanding the dynamics of cell population allows insight into the control mechanism of the growth and development of mammalian tissues. It is well known that the proliferation and differentiation among stem cells (SCs), intermediate progenitor cells (IPCs), and fully differentiated cells (FDCs) are under different activation and inhibition controls. Secreted factors in negative feedback loops have already been identified as major elements in regulating the numbers of different cell types and in maintaining the equilibrium of cell populations. We have developed a novel spatial dynamic model of cells. We can characterize not only overall cell population dynamics, but also details of temporal-spatial relationship of individual cells within a tissue. In our model, the shape, growth, and division of each cell are modeled using a realistic geometric model. Furthermore, the inhibited growth rate, proliferation and differentiation probabilities of individual cells are modeled through feedback loops controlled by secreted factors of neighboring cells within a proper diffusion radius. With specific proliferation and differentiation probabilities, the actual division type that each cell will take is chosen by a Monte Carlo sampling process. With simulations we found that with proper strengths of inhibitions to growth and stem cell divisions, the whole tissue is capable of achieving a homeostatic size control. We discuss our findings on control mechanisms of the stability of the tissue development. Our model can be applied to study broad issues on tissue development and pattern formation in stem cell and cancer research. PMID:23367175

Cao, Youfang; Liang, Claire; Naveed, Hammad; Li, Yingzi; Chen, Meng; Nie, Qing

2012-01-01

173

Birds have paedomorphic dinosaur skulls.  

PubMed

The interplay of evolution and development has been at the heart of evolutionary theory for more than a century. Heterochrony—change in the timing or rate of developmental events—has been implicated in the evolution of major vertebrate lineages such as mammals, including humans. Birds are the most speciose land vertebrates, with more than 10,000 living species representing a bewildering array of ecologies. Their anatomy is radically different from that of other vertebrates. The unique bird skull houses two highly specialized systems: the sophisticated visual and neuromuscular coordination system allows flight coordination and exploitation of diverse visual landscapes, and the astonishing variations of the beak enable a wide range of avian lifestyles. Here we use a geometric morphometric approach integrating developmental, neontological and palaeontological data to show that the heterochronic process of paedomorphosis, by which descendants resemble the juveniles of their ancestors, is responsible for several major evolutionary transitions in the origin of birds. We analysed the variability of a series of landmarks on all known theropod dinosaur skull ontogenies as well as outgroups and birds. The first dimension of variability captured ontogeny, indicating a conserved ontogenetic trajectory. The second dimension accounted for phylogenetic change towards more bird-like dinosaurs. Basally branching eumaniraptorans and avialans clustered with embryos of other archosaurs, indicating paedomorphosis. Our results reveal at least four paedomorphic episodes in the history of birds combined with localized peramorphosis (development beyond the adult state of ancestors) in the beak. Paedomorphic enlargement of the eyes and associated brain regions parallels the enlargement of the nasal cavity and olfactory brain in mammals. This study can be a model for investigations of heterochrony in evolutionary transitions, illuminating the origin of adaptive features and inspiring studies of developmental mechanisms. PMID:22722850

Bhullar, Bhart-Anjan S; Marugán-Lobón, Jesús; Racimo, Fernando; Bever, Gabe S; Rowe, Timothy B; Norell, Mark A; Abzhanov, Arhat

2012-07-12

174

HDAC1 regulates pluripotency and lineage specific transcriptional networks in embryonic and trophoblast stem cells  

PubMed Central

Epigenetic regulation of gene expression is important in maintaining self-renewal of embryonic stem (ES) and trophoblast stem (TS) cells. Histone deacetylases (HDACs) negatively control histone acetylation by removing covalent acetylation marks from histone tails. Because histone acetylation is a known mark for active transcription, HDACs presumably associate with inactive genes. Here, we used genome-wide chromatin immunoprecipitation to investigate targets of HDAC1 in ES and TS cells. Through evaluation of genes associated with acetylated histone H3 marks, and global expression analysis of Hdac1 knockout ES and trichostatin A-treated ES and TS cells, we found that HDAC1 occupies mainly active genes, including important regulators of ES and TS cells self-renewal. We also observed occupancy of methyl-CpG binding domain protein 3 (MBD3), a subunit of the nucleosome remodeling and histone deacetylation (NuRD) complex, at a subset of HDAC1-occupied sequences in ES cells, including the pluripotency regulators Oct4, Nanog and Kfl4. By mapping HDAC1 targets on a global scale, our results describe further insight into epigenetic mechanisms of ES and TS cells self-renewal.

Kidder, Benjamin L.; Palmer, Stephen

2012-01-01

175

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

2012-05-24

176

The evolution of dinosaurs.  

PubMed

The ascendancy of dinosaurs on land near the close of the Triassic now appears to have been as accidental and opportunistic as their demise and replacement by therian mammals at the end of the Cretaceous. The dinosaurian radiation, launched by 1-meter-long bipeds, was slower in tempo and more restricted in adaptive scope than that of therian mammals. A notable exception was the evolution of birds from small-bodied predatory dinosaurs, which involved a dramatic decrease in body size. Recurring phylogenetic trends among dinosaurs include, to the contrary, increase in body size. There is no evidence for co-evolution between predators and prey or between herbivores and flowering plants. As the major land masses drifted apart, dinosaurian biogeography was molded more by regional extinction and intercontinental dispersal than by the breakup sequence of Pangaea. PMID:10381873

Sereno, P C

1999-06-25

177

Making Tracks: Dinosaur Footprints  

NSDL National Science Digital Library

In this lesson, students will learn about the occurrence of dinosaur tracks and their usefulness in studying these extinct creatures. Background materials discuss early discoveries of dinosaur footprints and point out that there are many more fossil footprints than there are fossil skeletons or bones, making them more likely to be discovered. There is also discussion of the information that scientists can gather from these fossils: anatomical details; behavior, social structure and physical environment; the way the animal moved; and their approximate speed. The lesson includes an activity in which students calculate the length of an animal's leg from measurements taken from their footprints. A downloadable, printable version is provided.

178

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

179

First spinosaurid dinosaur from Australia and the cosmopolitanism of Cretaceous dinosaur faunas.  

PubMed

A cervical vertebra from the Early Cretaceous of Victoria represents the first Australian spinosaurid theropod dinosaur. This discovery significantly extends the geographical range of spinosaurids, suggesting that the clade obtained a near-global distribution before the onset of Pangaean fragmentation. The combined presence of spinosaurid, neovenatorid, tyrannosauroid and dromaeosaurid theropods in the Australian Cretaceous undermines previous suggestions that the dinosaur fauna of this region was either largely endemic or predominantly 'Gondwanan' in composition. Many lineages are well-represented in both Laurasia and Gondwana, and these observations suggest that Early-'middle' Cretaceous theropod clades possessed more cosmopolitan distributions than assumed previously, and that caution is necessary when attempting to establish palaeobiogeographic patterns on the basis of a patchily distributed fossil record. PMID:21693488

Barrett, Paul M; Benson, Roger B J; Rich, Thomas H; Vickers-Rich, Patricia

2011-06-21

180

First spinosaurid dinosaur from Australia and the cosmopolitanism of Cretaceous dinosaur faunas  

PubMed Central

A cervical vertebra from the Early Cretaceous of Victoria represents the first Australian spinosaurid theropod dinosaur. This discovery significantly extends the geographical range of spinosaurids, suggesting that the clade obtained a near-global distribution before the onset of Pangaean fragmentation. The combined presence of spinosaurid, neovenatorid, tyrannosauroid and dromaeosaurid theropods in the Australian Cretaceous undermines previous suggestions that the dinosaur fauna of this region was either largely endemic or predominantly ‘Gondwanan’ in composition. Many lineages are well-represented in both Laurasia and Gondwana, and these observations suggest that Early–‘middle’ Cretaceous theropod clades possessed more cosmopolitan distributions than assumed previously, and that caution is necessary when attempting to establish palaeobiogeographic patterns on the basis of a patchily distributed fossil record.

Barrett, Paul M.; Benson, Roger B. J.; Rich, Thomas H.; Vickers-Rich, Patricia

2011-01-01

181

Arthropod phylogeny: onychophoran brain organization suggests an archaic relationship with a chelicerate stem lineage  

PubMed Central

Neuroanatomical studies have demonstrated that the architecture and organization among neuropils are highly conserved within any order of arthropods. The shapes of nerve cells and their neuropilar arrangements provide robust characters for phylogenetic analyses. Such analyses so far have agreed with molecular phylogenies in demonstrating that entomostracans+malacostracans belong to a clade (Tetraconata) that includes the hexapods. However, relationships among what are considered to be paraphyletic groups or among the stem arthropods have not yet been satisfactorily resolved. The present parsimony analyses of independent neuroarchitectural characters from 27 arthropods and lobopods demonstrate relationships that are congruent with phylogenies derived from molecular studies, except for the status of the Onychophora. The present account describes the brain of the onychophoran Euperipatoides rowelli, demonstrating that the structure and arrangements of its neurons, cerebral neuropils and sensory centres are distinct from arrangements in the brains of mandibulates. Neuroanatomical evidence suggests that the organization of the onychophoran brain is similar to that of the brains of chelicerates.

Strausfeld, Nicholas J; Mok Strausfeld, Camilla; Loesel, Rudi; Rowell, David; Stowe, Sally

2006-01-01

182

Housekeeping gene stability influences the quantification of osteogenic markers during stem cell differentiation to the osteogenic lineage  

PubMed Central

Real-time reverse transcription PCR (RT-qPCR) relies on a housekeeping or normalizer gene whose expression remains constant throughout the experiment. RT-qPCR is commonly used for characterization of human bone marrow mesenchymal stem cells (hBMSCs). However, to the best of our knowledge, there are no studies validating the expression stability of the genes used as normalizers during hBMSCs differentiation. This work aimed to study the stability of the housekeeping genes ?-actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and ribosomal protein L13A (RPL13A) during the osteogenic differentiation of hBMSCs. Their stability was evaluated via RT-qPCR in 14 and 20 day differentiation assays to the osteogenic lineage. Different normalization strategies were evaluated to quantify the osteogenic markers collagen type I, bone sialoprotein and osteonectin. Cell differentiation was confirmed via alizarin red staining. The results demonstrated up-regulation of ?-actin with maximum fold changes (MFC) of 4.38. GAPDH and RPL13A were not regulated by osteogenic media after 14 days and presented average fold changes lower than 2 in 20 day cultures. RPL13A (MFC < 2) had a greater stability when normalizing as a function of culture time compared with GAPDH (MFC ? 2.2), which resulted in expression patterns of the osteogenic markers more consistent with the observed differentiation process. The results suggest that ?-actin regulation could be associated with the morphological changes characteristic of hBMSCs osteogenic differentiation, and provide evidence for the superior performance of RPL13A as a normalizer gene in osteogenic differentiation studies of hBMSCs. This work highlights the importance of validating the normalizer genes used for stem cells characterization via RT-qPCR.

Posada, Olga M.; Gallego-Perez, Daniel; Higuita-Castro, Natalia; Sarassa, Carlos; Hansford, Derek J.; Agudelo-Florez, Piedad; Lopez, Luis E.

2010-01-01

183

Differentiation of murine embryonic stem cells toward renal lineages by conditioned medium from ureteric bud cells in vitro.  

PubMed

The kidney is formed from two tissue populations derived from the intermediate mesoderm, the ureteric bud, and the metanephric mesenchyme. Metanephric mesenchyme is a pluripotent renal stem population, and conversion of renal mesenchyme into epithelia depends on the ureteric bud in vivo and in vitro. Embryonic stem (ES) cells have been induced to differentiate into a broad spectrum of specialized cell types in vitro, including hematopoietic, pancreatic, and neuronal cells. Such ES-derived cells can provide a valuable source of progenitor cells. However, whether ES cells can be stimulated by factors secreted from the fetal renal cells to differentiate into renal precursor cells in vitro has not been reported. In this study, we showed that murine ES cells can give rise to embryoid bodies in the absence of leukemia inhibitory factor. Culture conditions were optimized [6 days, 10 ng/ml activin and 10(-7) M retinoic acid (RA)] to generate maximal mesoderm populations specifically expressing Pax2 and brachyury. Results showed that 72% of the cells were brachyury positive by fluorescent activated cell sorter on Day 6 of EB cell differentiation. Conditioned medium collected from cultures of ureteric bud cells from renal cells of a 13-day-old fetus was added to the culture medium. Mesoderm cells were cultured for up to 10 days before showing expression of renal markers, initiation of nephrogenesis (WT-1 and Pax2), and terminally differentiated renal cell types (POD-1 and E-cadherin). This study suggests that ES cells pre-treated by RA and activin can interact with secreted molecules of the fetal renal cells to specifically differentiate into renal precursor cells. Our results provide an experimental basis for the development of in vitro assays to steer differentiation of ES cells toward renal lineages. PMID:20705585

Ren, Xiaohui; Zhang, Jingya; Gong, Xiaowen; Niu, Xin; Zhang, Xuejin; Chen, Peng; Zhang, Xuejun

2010-06-08

184

Human Embryonic and Fetal Mesenchymal Stem Cells Differentiate toward Three Different Cardiac Lineages in Contrast to Their Adult Counterparts  

PubMed Central

Mesenchymal stem cells (MSCs) show unexplained differences in differentiation potential. In this study, differentiation of human (h) MSCs derived from embryonic, fetal and adult sources toward cardiomyocytes, endothelial and smooth muscle cells was investigated. Labeled hMSCs derived from embryonic stem cells (hESC-MSCs), fetal umbilical cord, bone marrow, amniotic membrane and adult bone marrow and adipose tissue were co-cultured with neonatal rat cardiomyocytes (nrCMCs) or cardiac fibroblasts (nrCFBs) for 10 days, and also cultured under angiogenic conditions. Cardiomyogenesis was assessed by human-specific immunocytological analysis, whole-cell current-clamp recordings, human-specific qRT-PCR and optical mapping. After co-culture with nrCMCs, significantly more hESC-MSCs than fetal hMSCs stained positive for ?-actinin, whereas adult hMSCs stained negative. Furthermore, functional cardiomyogenic differentiation, based on action potential recordings, was shown to occur, but not in adult hMSCs. Of all sources, hESC-MSCs expressed most cardiac-specific genes. hESC-MSCs and fetal hMSCs contained significantly higher basal levels of connexin43 than adult hMSCs and co-culture with nrCMCs increased expression. After co-culture with nrCFBs, hESC-MSCs and fetal hMSCs did not express ?-actinin and connexin43 expression was decreased. Conduction velocity (CV) in co-cultures of nrCMCs and hESC-MSCs was significantly higher than in co-cultures with fetal or adult hMSCs. In angiogenesis bioassays, only hESC-MSCs and fetal hMSCs were able to form capillary-like structures, which stained for smooth muscle and endothelial cell markers.Human embryonic and fetal MSCs differentiate toward three different cardiac lineages, in contrast to adult MSCs. Cardiomyogenesis is determined by stimuli from the cellular microenvironment, where connexin43 may play an important role.

Ramkisoensing, Arti A.; Pijnappels, Daniel A.; Askar, Said F. A.; Passier, Robert; Swildens, Jim; Goumans, Marie Jose; Schutte, Cindy I.; de Vries, Antoine A. F.; Scherjon, Sicco; Mummery, Christine L.; Schalij, Martin J.; Atsma, Douwe E.

2011-01-01

185

SOX2 regulates YAP1 to maintain stemness and determine cell fate in the osteo-adipo lineage.  

PubMed

The osteoblastic and adipocytic lineages arise from mesenchymal stem cells (MSCs), but few regulators of self-renewal and early cell-fate decisions are known. Here, we show that the Hippo pathway effector YAP1 is a direct target of SOX2 and can compensate for the self-renewal defect caused by SOX2 inactivation in osteoprogenitors and MSCs. Osteogenesis is blocked by high SOX2 or YAP1, accelerated by depletion of either one, and the inhibition of osteogenesis by SOX2 requires YAP1. SOX2 favors adipogenesis and induces PPAR?, but adipogenesis can only occur with moderate levels of YAP1. YAP1 induction by SOX2 is restrained in adipogenesis, and both YAP1 overexpression and depletion inhibit the process. YAP1 binds ?-catenin and directly induces the Wnt antagonist Dkk1 to dampen pro-osteogenic Wnt signals. We demonstrate a Hippo-independent regulation of YAP1 by SOX2 that cooperatively antagonizes Wnt/?-catenin signals and regulates PPAR? to determine osteogenic or adipocytic fates. PMID:23791527

Seo, Eunjeong; Basu-Roy, Upal; Gunaratne, Preethi H; Coarfa, Cristian; Lim, Dae-Sik; Basilico, Claudio; Mansukhani, Alka

2013-06-20

186

Estradiol promotes neural stem cell differentiation into endothelial lineage and angiogenesis in injured peripheral nerve  

PubMed Central

Neural stem cells (NSCs) differentiate into endothelial cells (ECs) and neuronal cells. Estradiol (E2) is known to exhibit proangiogenic effects on ischemic tissues via EC activation. Therefore, we hypothesized that E2 can promote the therapeutic potential of NSC transplantation for injured nerve repair via the differentiation of NSCs into ECs during neovascularization. NSCs isolated from newborn mouse brains were transplanted into injured sciatic nerves with (NSC/E2 group) or without E2-conjugated gelatin hydrogel (E2 group). The NSC/E2 group exhibited the greatest recovery in motor nerve conduction velocity, voltage amplitude, and exercise tolerance. Histological analyses revealed increased intraneural vascularity and blood perfusion as well as striking NSC recruitment to the neovasculature in the injured nerves in the NSC/E2 group. In vitro, E2 enhanced the NSC migration and proliferation inhibiting apoptosis. Fluorescence-activated cell sorting analysis also revealed that E2 significantly increased the percentage of CD31 in NSCs, and the effect of E2 was completely neutralized by the estrogen receptor antagonist ICI. The combination of E2 administration and NSC transplantation cooperatively improved the functional recovery of injured peripheral nerves, at least in part, via E2-associated NSC differentiation into ECs. These findings provide a novel mechanistic insight into both NSC biology and the biological effects of endogenous E2.

Sekiguchi, Haruki; Jujo, Kentaro; Thorne, Tina; Ito, Aiko; Klyachko, Ekaterina; Hamada, Hiromichi; Kessler, John A.; Tabata, Yasuhiko; Kawana, Masatoshi; Asahi, Michio; Hagiwara, Nobuhisa; Losordo, Douglas W.

2013-01-01

187

Transgenic human fetal fibroblasts as feeder layer for human embryonic stem cell lineage selection.  

PubMed

Successful gene targeting in human embryonic stem (hES) cells requires the use of primary fibroblast feeder layers, which assist in the maintenance of the pluripotent state of hES cells. Such feeder layers must also survive any further selection strategy for hES cells. Here we report the production of a novel transgenic human fetal fibroblast (tHFF) as a feeder layer that is resistant to puromycin and can be used for gene targeting and selection of positive clones in hES cells. tHFFs survive under a wide range of puromycin concentrations (0.5-2 microg/ml) and also supports the undifferentiated growth of hES cells. We have demonstrated here that tHFFs are suitable for selecting Envy-hES cells that were transfected with a green fluorescent protein-small interfering RNA (GFP-siRNA) plasmid construct to induce GFP gene down-regulation. The later studies were designed to isolate and propagate stably knockdown cells. tHFFs thus can be used for targeting other genes that would serve as a model to select and understand the differentiation process in hES cells. PMID:17105409

Sidhu, Kuldip S; Lie, Khun Hong D; Tuch, Bernard E

2006-10-01

188

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

2008-08-15

189

Red ginseng extract facilitates the early differentiation of human embryonic stem cells into mesendoderm lineage.  

PubMed

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

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

2010-09-01

190

Early cretaceous dinosaurs from the sahara.  

PubMed

A major question in Mesozoic biogeography is how the land-based dinosaurian radiation responded to fragmentation of Pangaea. A rich fossil record has been uncovered on northern continents that spans the Cretaceous, when continental isolation reached its peak. In contrast, dinosaur remains on southern continents are scarce. The discovery of dinosaurian skeletons from Lower Cretaceous beds in the southern Sahara shows that several lineages of tetanuran theropods and broad-toothed sauropods had a cosmopolitan distribution across Pangaea before the onset of continental fragmentation. The distinct dinosaurian faunas of Africa, South America, and Asiamerica arose during the Cretaceous by differential survival of once widespread lineages on land masses that were becoming increasingly isolated from one another. PMID:17771449

Sereno, P C; Wilson, J A; Larsson, H C; Dutheil, D B; Sues, H D

1994-10-14

191

Songs the Dinosaurs Sang!.  

ERIC Educational Resources Information Center

|Presents a lesson plan that uses a constructivist approach for developing and challenging students' different thinking strengths. In the context of musical and bodily-kinesthetic thinking, elementary school students interpret the sounds and movements the dinosaurs made as they negotiated their primitive environments. (CR)|

Greenwald, Nina L.

1998-01-01

192

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

193

Dinosaur Bone Experiments  

NSDL National Science Digital Library

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

Science, Lawrence H.

2005-01-01

194

[MicroRNA-10a accelerates endodermal lineage differentiation of mesenchymal stem cells from human placenta].  

PubMed

Objective To improve the potential of endodermal differentiation of human placenta-derived mesenchymal stem cells (PMSCs) by microRNA-10a (miR-10a)-mediated post-transcriptional regulation of its mRNA targets. Methods Lentiviral vectors were used to stably and specifically over-express miR-10a and inhibited the miR-10a function by its antagomir. In addition, the relationship between miR-10a and Hoxa1 expression was analyzed. Real-time quantitative PCR (qRT-PCR) and immunofluorescent cytochemical staining were utilized to test the mRNA and protein expression variation and assess the ability of PMSCs to differentiate into endodermal cells. Results Over-expression of miR-10a led to the suppression of endogenous Hoxa1 expression, and inhibition of miR-10a relieved the repression of Hoxa1. Over-expression of miR-10a in PMSCs resulted in the up-regulation of endoderm-specific genes (FoxA2, Sox-17, Pdx-1 and Cdx2) and the increased proportions of FOXA2, SOX-17 and PDX-1 positive events as compared with the control treated cells. Conclusion miR-10a was up-regulated during endodermal differentiation of PMSCs and involved in its differentiation partially via the suppression of the Hoxa1 gene. Furthermore, the miR-10a accelerates endodermal differentiation, likely mediated by the up-reguation of endoderm-specific down-stream genes. PMID:24103260

Chen, Dongmei; Ma, Haibin; Liu, Shudan; Wang, Libin; Li, Yukui; Wei, Jun

2013-10-01

195

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.

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

2006-01-01

196

High throughput transcriptome profiling of lithium stimulated human mesenchymal stem cells reveals priming towards osteoblastic lineage.  

PubMed

Human mesenchymal stem cells (hMSCs) present in the bone marrow are the precursors of osteoblasts, chondrocytes and adipocytes, and hold tremendous potential for osteoregenerative therapy. However, achieving directed differentiation into osteoblasts has been a major concern. The use of lithium for enhancing osteogenic differentiation has been documented in animal models but its effect in humans is not clear. We, therefore, performed high throughput transcriptome analysis of lithium-treated hMSCs to identify altered gene expression and its relevance to osteogenic differentiation. Our results show suppression of proliferation and enhancement of alkaline phosphatase (ALP) activity upon lithium treatment of hMSCs under non-osteogenic conditions. Microarray profiling of lithium-stimulated hMSC revealed decreased expression of adipogenic genes (CEBPA, CMKLR1, HSD11B1) and genes involved in lipid biosynthesis. Interestingly, osteoclastogenic factors and immune responsive genes (IL7, IL8, CXCL1, CXCL12, CCL20) were also downregulated. Negative transcriptional regulators of the osteogenic program (TWIST1 and PBX1) were suppressed while genes involved in mineralization like CLEC3B and ATF4 were induced. Gene ontology analysis revealed enrichment of upregulated genes related to mesenchymal cell differentiation and signal transduction. Lithium priming led to enhanced collagen 1 synthesis and osteogenic induction of lithium pretreated MSCs resulted in enhanced expression of Runx2, ALP and bone sialoprotein. However, siRNA-mediated knockdown of RRAD, CLEC3B and ATF4 attenuated lithium-induced osteogenic priming, identifying a role for RRAD, a member of small GTP binding protein family, in osteoblast differentiation. In conclusion, our data highlight the transcriptome reprogramming potential of lithium resulting in higher propensity of lithium "primed" MSCs for osteoblastic differentiation. PMID:23383279

Satija, Neeraj Kumar; Sharma, Deepa; Afrin, Farhat; Tripathi, Rajendra P; Gangenahalli, Gurudutta

2013-01-30

197

Angiogenic CXC chemokine expression during differentiation of human mesenchymal stem cells towards the osteoblastic lineage.  

PubMed

The potential role of ELR(+) CXC chemokines in early events in bone repair was studied using human mesenchymal stem cells (hMSCs). Inflammation, which occurs in the initial phase of tissue healing in general, is critical to bone repair. Release of cytokines from infiltrating immune cells and injured bone can lead to recruitment of MSCs to the region of repair. CXC chemokines bearing the Glu-Leu-Arg (ELR) motif are also released by inflammatory cells and serve as angiogenic factors stimulating chemotaxis and proliferation of endothelial cells. hMSCs, induced to differentiate with osteogenic medium (OGM) containing ascorbate, beta-glycerophosphate (beta-GP), and dexamethasone (DEX), showed an increase in mRNA and protein secretion of the ELR(+) CXC chemokines CXCL8 and CXCL1. CXCL8 mRNA half-life studies reveal an increase in mRNA stability upon OGM stimulation. Increased expression and secretion is a result of DEX in OGM and is dose-dependent. Inhibition of the glucocorticoid receptor with mifepristone only partially inhibits DEX-stimulated CXCL8 expression indicating both glucocorticoid receptor dependent and independent pathways. Treatment with signal transduction inhibitors demonstrate that this expression is due to activation of the ERK and p38 mitogen-activated protein kinase (MAPK) pathways and is mediated through the G(alphai)-coupled receptors. Angiogenesis assays demonstrate that OGM-stimulated conditioned media containing secreted CXCL8 and CXCL1 can induce angiogenesis of human microvascular endothelial cells in an in vitro Matrigel assay. PMID:17583554

Bischoff, D S; Zhu, J H; Makhijani, N S; Kumar, A; Yamaguchi, D T

2008-02-15

198

In situ lineage tracking of human prostatic epithelial stem cell fate reveals a common clonal origin for basal and luminal cells.  

PubMed

Stem cells accumulate mitochondrial DNA (mtDNA) mutations resulting in an observable respiratory chain defect in their progeny, allowing the mapping of stem cell fate. There is considerable uncertainty in prostate epithelial biology where both basal and luminal stem cells have been described, and in this study the clonal relationships within the human prostate epithelial cell layers were explored by tracing stem cell fate. Fresh-frozen and formalin-fixed histologically-benign prostate samples from 35 patients were studied using sequential cytochrome c oxidase (COX)/succinate dehydrogenase (SDH) enzyme histochemistry and COX subunit I immunofluorescence to identify areas of respiratory chain deficiency; mtDNA mutations were identified by whole mitochondrial genome sequencing of laser-captured areas. We demonstrated that cells with respiratory chain defects due to somatic mtDNA point mutations were present in prostate epithelia and clonally expand in acini. Lineage tracing revealed distinct patterning of stem cell fate with mtDNA mutations spreading throughout the whole acinus or, more commonly, present as mosaic acinar defects. This suggests that individual acini are typically generated from multiple stem cells, and the presence of whole COX-deficient acini suggests that a single stem cell can also generate an entire branching acinar subunit of the gland. Significantly, a common clonal origin for basal, luminal and neuroendocrine cells is demonstrated, helping to resolve a key area of debate in human prostate stem cell biology. PMID:21898876

Blackwood, John K; Williamson, Stuart C; Greaves, Laura C; Wilson, Laura; Rigas, Anastasia C; Sandher, Raveen; Pickard, Robert S; Robson, Craig N; Turnbull, Douglass M; Taylor, Robert W; Heer, Rakesh

2011-10-01

199

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

PubMed

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

2012-10-26

200

There is more to a lipid than just being a fat: sphingolipid-guided differentiation of oligodendroglial lineage from embryonic stem cells  

PubMed Central

Dr. Robert K. Yu's research showed for the first time that the composition of glycosphingolipids is tightly regulated during embryo development. Studies in our group showed that the glycosphingolipid precursor ceramide is also critical for stem cell differentiation and apoptosis. Our new studies suggest that ceramide and its derivative, sphingosine-1-phosphate (S1P), act synergistically on embryonic stem (ES) cell differentiation. When using neural precursor cells (NPCs) derived from ES cells for transplantation, residual pluripotent stem (rPS) cells pose a significant risk of tumor formation after stem cell transplantation. We show here that rPS cells did not express the S1P receptor S1P1, which left them vulnerable to ceramide or ceramide analog (N-oleoyl serinol or S18)-induced apoptosis. In contrast, ES cell-derived NPCs expressed S1P1 and were protected in the presence of S1P or its pro-drug analog FTY720. Consistent with previous studies, FTY720-treated NPCs differentiated predominantly toward oligodendroglial lineage as tested by the expression of the oligodendrocyte precursor cell (OPC) markers Olig2 and O4. As the consequence, a combined administration of S18 and FTY720 to differentiating ES cells eliminated rPS cells and promoted oligodendroglial differentiation. In addition, we show that this combination promoted differentiation of ES cell-derived NPCs toward oligodendroglial lineage in vivo after transplantation into mouse brain.

Bieberich, Erhard

2013-01-01

201

Did dinosaurs invent flowers? Dinosaur-angiosperm coevolution revisited.  

PubMed

Angiosperms first appeared in northern Gondwana during the Early Cretaceous, approximately 135 million years ago. Several authors have hypothesised that the origin of angiosperms, and the tempo and pattern of their subsequent radiation, was mediated by changes in the browsing behaviour of large herbivorous dinosaurs (sauropods and ornithischians). Moreover, the taxonomic and ecological radiation of angiosperms has been associated with the evolution of complex jaw mechanisms among ornithischian dinosaurs. Here, we review critically the evidence for dinosaur-angiosperm interactions during the Cretaceous Period, providing explicit spatiotemporal comparisons between evolutionary and palaeoecological events in both the dinosaur and angiosperm fossil records and an assessment of the direct and indirect evidence for dinosaur diets. We conclude that there are no strong spatiotemporal correlations in support of the hypothesis that dinosaurs were causative agents in the origin of angiosperms; however, dinosaur-angiosperm interactions in the Late Cretaceous may have resulted in some coevolutionary interactions, although direct evidence of such interactions is scanty at present. It is likely that other animal groups (insects, arboreal mammals) had a greater impact on angiosperm diversity during the Cretaceous than herbivorous dinosaurs. Elevated levels of atmospheric CO2 might have played a critical role in the initial stages of the angiosperm radiation. PMID:11569792

Barrett, P M; Willis, K J

2001-08-01

202

Shoebox Dinosaur Dig Site  

NSDL National Science Digital Library

In this activity, (on page 6 of the PDF) learners participate in a hands-on fossil excavation. Groups of learners will receive a shoebox full off sand in which several chicken bones have been buried at various levels. After preparing string grid lines over the âdig site,â they will carefully brush away sand and record observations as each bone is discovered. Relates to linked video, DragonflyTV GPS: Dinosaurs.

Twin Cities Public Television, Inc.

2006-01-01

203

What Killed the Dinosaurs?  

NSDL National Science Digital Library

Definitive answers to some of life's most enduring questions are often difficult or impossible to come by. However, scientific processes piece together the information that is available as a way of providing alternative explanations for a wide variety of phenomena. This interactive activity from the Evolution Web site outlines the evidence gathered to explain what caused the extinction of the dinosaurs 65 million years ago. It proposes four possible hypotheses and invites you to consider the evidence and come to your own conclusion.

Foundation, Wgbh E.

2009-07-22

204

The Extinction of the Dinosaurs  

Microsoft Academic Search

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

MICHAEL J. OARD

1997-01-01

205

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

206

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

207

Dinosaurs nesting on tidal flats  

Microsoft Academic Search

The discovery of a dinosaur clutch in Upper Cretaceous tidal flat deposits in the Tremp Formation in Biscarri, Isona (Lleida, Spain), provides insight into the mode of life of some dinosaurs. The clutch occurs in grey marls that were originally waterlogged, muddy sediments. The seven elongated eggs are parallel to each other and with their long axis almost vertically oriented.

N. López-Mart??nez; J. J. Moratalla; J. L. Sanz

2000-01-01

208

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.

209

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

210

CpG methylation profiles of endothelial cell-specific gene promoter regions in adipose tissue stem cells suggest limited differentiation potential toward the endothelial cell lineage.  

PubMed

In vivo endothelial commitment of adipose stem cells (ASCs) has scarcely been reported, and controversy remains on the contribution of ASCs to vascularization. We address the epigenetic commitment of ASCs to the endothelial lineage. We report a bisulfite sequencing analysis of CpG methylation in the promoters of two endothelial-cell-specific genes, CD31 and CD144, in freshly isolated and in cultures of ASCs before and after induction of endothelial differentiation. In contrast to adipose tissue-derived endothelial (CD31(+)) cells, freshly isolated ASCs display a heavily methylated CD31 promoter and a mosaically methylated CD144 promoter despite basal transcription of both genes. Methylation state of both promoters remains globally stable upon culture. Endothelial stimulation of ASCs in methylcellulose elicits phenotypic changes, marginal upregulation of CD31, and CD144 expression and restrictive induction of a CD31(+)CD144(+) immunophenotype. These events are accompanied by discrete changes in CpG methylation in CD31 and CD144 promoters; however, no global demethylation that marks CD31(+) cells and human umbilical vein endothelial cells occurs. Immunoselection of CD31(+) cells after endothelial stimulation reveals consistent demethylation of one CpG immediately 3' of the transcription start site of the CD31 promoter. Adipogenic or osteogenic differentiation maintains CD31 and CD144 methylation patterns of undifferentiated cells. Methylation profiles of CD31 and CD144 promoters suggest a limited commitment of ASCs to the endothelial lineage. This contrasts with the reported hypomethylation of adipogenic promoters, which reflects a propensity of ASCs toward adipogenic differentiation. Analysis of CpG methylation at lineage-specific promoters provides a robust assessment of epigenetic commitment of stem cells to a specific lineage. PMID:17170064

Boquest, Andrew C; Noer, Agate; Sørensen, Anita L; Vekterud, Kristin; Collas, Philippe

2006-12-14

211

Activin, BMP and FGF pathways cooperate to promote endoderm and pancreatic lineage cell differentiation from human embryonic stem cells.  

PubMed

The study of how human embryonic stem cells (hESCs) differentiate into insulin-producing beta cells has twofold significance: first, it provides an in vitro model system for the study of human pancreatic development, and second, it serves as a platform for the ultimate production of beta cells for transplantation into patients with diabetes. The delineation of growth factor interactions regulating pancreas specification from hESCs in vitro is critical to achieving these goals. In this study, we describe the roles of growth factors bFGF, BMP4 and Activin A in early hESC fate determination. The entire differentiation process is carried out in serum-free chemically-defined media (CDM) and results in reliable and robust induction of pancreatic endoderm cells, marked by PDX1, and cell clusters co-expressing markers characteristic of beta cells, including PDX1 and insulin/C-peptide. Varying the combinations of growth factors, we found that treatment of hESCs with bFGF, Activin A and BMP4 (FAB) together for 3-4days resulted in strong induction of primitive-streak and definitive endoderm-associated genes, including MIXL1, GSC, SOX17 and FOXA2. Early proliferative foregut endoderm and pancreatic lineage cells marked by PDX1, FOXA2 and SOX9 expression are specified in EBs made from FAB-treated hESCs, but not from Activin A alone treated cells. Our results suggest that important tissue interactions occur in EB-based suspension culture that contribute to the complete induction of definitive endoderm and pancreas progenitors. Further differentiation occurs after EBs are embedded in Matrigel and cultured in serum-free media containing insulin, transferrin, selenium, FGF7, nicotinamide, islet neogenesis associated peptide (INGAP) and exendin-4, a long acting GLP-1 agonist. 21-28days after embedding, PDX1 gene expression levels are comparable to those of human islets used for transplantation, and many PDX1(+) clusters are formed. Almost all cells in PDX1(+) clusters co-express FOXA2, HNF1ß, HNF6 and SOX9 proteins, and many cells also express CPA1, NKX6.1 and PTF1a. If cells are then switched to medium containing B27 and nicotinamide for 7-14days, then the number of insulin(+) cells increases markedly. Our study identifies a new chemically defined culture protocol for inducing endoderm- and pancreas-committed cells from hESCs and reveals an interplay between FGF, Activin A and BMP signaling in early hESC fate determination. PMID:21855631

Xu, Xiaofang; Browning, Victoria L; Odorico, Jon S

2011-08-10

212

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

213

Molecular signatures of the three stem cell lineages in hydra and the emergence of stem cell function at the base of multicellularity.  

PubMed

How distinct stem cell populations originate and whether there is a clear stem cell "genetic signature" remain poorly understood. Understanding the evolution of stem cells requires molecular profiling of stem cells in an animal at a basal phylogenetic position. In this study, using transgenic Hydra polyps, we reveal for each of the three stem cell populations a specific signature set of transcriptions factors and of genes playing key roles in cell type-specific function and interlineage communication. Our data show that principal functions of stem cell genes, such as maintenance of stemness and control of stem cell self-renewal and differentiation, arose very early in metazoan evolution. They are corroborating the view that stem cell types shared common, multifunctional ancestors, which achieved complexity through a stepwise segregation of function in daughter cells. PMID:22595987

Hemmrich, Georg; Khalturin, Konstantin; Boehm, Anna-Marei; Puchert, Malte; Anton-Erxleben, Friederike; Wittlieb, Jörg; Klostermeier, Ulrich C; Rosenstiel, Philip; Oberg, Hans-Heinrich; Domazet-Loso, Tomislav; Sugimoto, Toshimi; Niwa, Hitoshi; Bosch, Thomas C G

2012-05-16

214

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

215

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.

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

2009-01-01

216

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.

217

Centering on Fossils and Dinosaurs.  

ERIC Educational Resources Information Center

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

Coble, Charles R.; McCall, Gregory K.

1986-01-01

218

The Extinction of the Dinosaurs  

Microsoft Academic Search

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

Michael J. oard

219

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.

220

Pluripotent Stem Cells Engrafted into the Normal or Lesioned Adult Rat Spinal Cord Are Restricted to a Glial Lineage  

Microsoft Academic Search

Proliferating populations of undifferentiated neural stem cells were isolated from the embryonic day 14 rat cerebral cortex or the adult rat subventricular zone. These cells were pluripotent through multiple passages, retaining the ability to differentiate in vitro into neurons, astrocytes, and oligodendrocytes. Two weeks to 2 months after engraftment of undifferentiated, BrdU-labeled stem cells into the normal adult spinal cord,

Qi-lin Cao; Y. Ping Zhang; Russell M. Howard; Winston M. Walters; Pantelis Tsoulfas; Scott R. Whittemore

2001-01-01

221

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

222

The Evolution and Extinction of the Dinosaurs  

Microsoft Academic Search

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 \\

David E. Fastovsky; David B. Weishampel

2005-01-01

223

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

224

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

225

SOX2 has a crucial role in the lineage determination and proliferation of mesenchymal stem cells through Dickkopf-1 and c-MYC  

PubMed Central

SOX2 is a well-known core transcription factor in embryonic stem cells (ESCs) and has an important role in the maintenance of pluripotency. Recently, SOX2 expression has also been reported in adult stem cells (ASCs), but the role of SOX2 in ASCs remains unknown. In this study, we examined the molecular mechanisms of SOX2 in human mesenchymal stem cells (hMSCs), a type of ASCs, by performing inhibition studies. SOX2 inhibition resulted in altered cell growth and differentiation capabilities. These changes coincided with a decrease in Dickkopf-1 (DKK1), a soluble inhibitor of WNT signaling. Chromatin immunoprecipitation and luciferase assays showed that SOX2 binds to DKK1 and has a positive regulatory role in transcription. The enforced expression of DKK1 in SOX2-inhibited hMSCs reversed the differentiation deformities, but could not abrogate the cell proliferation defect. Proliferation was regulated by c-MYC, whose expression can also be controlled by SOX2. Our study shows that SOX2 directly regulates DKK1 expression and, as a consequence, determines the differentiation lineage of hMSCs. Moreover, SOX2 also regulates proliferation by affecting c-MYC. Therefore, these results suggest that SOX2 might have a specific function by regulating DKK1 and c-MYC in the differentiation and growth of ASCs, which is separate from its roles in ESCs.

Park, S B; Seo, K W; So, A Y; Seo, M S; Yu, K R; Kang, S K; Kang, K S

2012-01-01

226

Plumage Color Patterns of an Extinct Dinosaur  

Microsoft Academic Search

For as long as dinosaurs have been known to exist, there has been speculation about their appearance. Fossil feathers can preserve the morphology of color-imparting melanosomes, which allow color patterns in feathered dinosaurs to be reconstructed. Here, we have mapped feather color patterns in a Late Jurassic basal paravian theropod dinosaur. Quantitative comparisons with melanosome shape and density in extant

Quanguo Li; Ke-Qin Gao; Jakob Vinther; Matthew D. Shawkey; Julia A. Clarke; Liliana D'Alba; Qingjin Meng; Derek E. G. Briggs; Richard O. Prum

2010-01-01

227

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.

228

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

229

Dinosaurs and the Cretaceous Terrestrial Revolution  

Microsoft Academic Search

The observed diversity 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 long been debated whether dinosaurs were part of the Cretaceous Terrestrial Revolution (KTR), from 125-80 Myr ago, when flowering plants, herbivorous and

Graeme T. Lloyd; Katie E. Davis; Davide Pisani; James E. Tarver; Marcello Ruta; Manabu Sakamoto; David W. E. Hone; Rachel Jennings; Michael J. Benton

2008-01-01

230

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

231

Stress hematopoiesis reveals abnormal control of self-renewal, lineage bias, and myeloid differentiation in Mll partial tandem duplication (Mll-PTD) hematopoietic stem/progenitor cells  

PubMed Central

One mechanism for disrupting the MLL gene in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) is through partial tandem duplication (MLL-PTD); however, the mechanism by which MLL-PTD contributes to MDS and AML development and maintenance is currently unknown. Herein, we investigated hematopoietic stem/progenitor cell (HSPC) phenotypes of Mll-PTD knock-in mice. Although HSPCs (Lin?Sca1+Kit+ (LSK)/SLAM+ and LSK) in MllPTD/WT mice are reduced in absolute number in steady state because of increased apoptosis, they have a proliferative advantage in colony replating assays, CFU-spleen assays, and competitive transplantation assays over wild-type HSPCs. The MllPTD/WT-derived phenotypic short-term (ST)–HSCs/multipotent progenitors and granulocyte/macrophage progenitors have self-renewal capability, rescuing hematopoiesis by giving rise to long-term repopulating cells in recipient mice with an unexpected myeloid differentiation blockade and lymphoid-lineage bias. However, MllPTD/WT HSPCs never develop leukemia in primary or recipient mice, suggesting that additional genetic and/or epigenetic defects are necessary for full leukemogenic transformation. Thus, the Mll-PTD aberrantly alters HSPCs, enhances self-renewal, causes lineage bias, and blocks myeloid differentiation. These findings provide a framework by which we can ascertain the underlying pathogenic role of MLL-PTD in the clonal evolution of human leukemia, which should facilitate improved therapies and patient outcomes.

Zhang, Yue; Yan, Xiaomei; Sashida, Goro; Zhao, Xinghui; Rao, Yalan; Goyama, Susumu; Whitman, Susan P.; Zorko, Nicholas; Bernot, Kelsie; Conway, Rajeana M.; Witte, David; Wang, Qian-fei; Tenen, Daniel G.; Xiao, Zhijian; Marcucci, Guido; Mulloy, James C.; Grimes, H. Leighton; Caligiuri, Michael A.

2012-01-01

232

Lineage-specific chimerism analysis in nucleated cells, T cells and natural killer cells after myeloablative allogeneic hematopoietic stem cell transplantation  

PubMed Central

Background Chimerism analysis is an important tool for assessing the origin of hematopoietic cells after allogeneic stem cell transplantation (allo-SCT) and can be used to detect impending graft rejection and the recurrence of underlying malignant or nonmalignant diseases. Methods This study included 24 patients who underwent myeloablative allo-SCT. DNA was extracted from nucleated cells (NCs), T cells, and natural killer (NK) cells, and the chimerism status of these cell fractions was determined by STR-PCR performed using an automated fluorescent DNA analyzer. Results Twenty-three out of the 24 patients achieved engraftment. Mixed chimerism (MC) in NCs, but not in T cells and NK cells, was significantly correlated with disease relapse. MC in all cell fractions was correlated with mortality. Ten patients (41.6%) developed extensive chronic GVHD. Six patients had MC in T cells, and 3 of them had chronic GVHD. Four patients with MC and relapse received donor lymphocyte infusion (DLI), and among them, 3 had secondary relapse. Further, the chimerism status differed among different cell lineages in 6 patients with myeloid malignancies. Conclusion The implications of MC in lymphocyte subsets are an important area for future research. Chimerism analysis in lineage-specific cells permits detection of relapse and facilitates the monitoring of therapeutic interventions. These results can provide the basic data for chimerism analysis after myeloablative SCT.

Goh, Ri-Young; Kim, Sung-Hyun

2011-01-01

233

Temporal profiling of the growth and multi-lineage potentiality of adipose tissue-derived mesenchymal stem cells cell-sheets.  

PubMed

Cell-sheet tissue engineering retains the benefits of an intact extracellular matrix (ECM) and can be used to produce scaffold-free constructs. Adipose tissue-derived stem cells (ASCs) are multipotent and more easily obtainable than the commonly used bone marrow-derived stem cells (BMSCs). Although BMSC cell sheets have been previously reported to display multipotentiality, a detailed study of the development and multilineage potential of ASC cell sheets (ASC-CSs) is non-existent in the literature. The aims of this study were to temporally profile: (a) the effect of hyperconfluent culture duration on ASC-CSs development; and (b) the multipotentiality of ASC-CSs by differentiation into the osteogenic, adipogenic and chondrogenic lineages. Rabbit ASCs were first isolated and cultured until confluence (day 0). The confluent cells were then cultured in ascorbic acid-supplemented medium for 3?weeks to study cell metabolic activity, cell sheet thickness and early differentiation gene expressions at weekly time points. ASC-CSs and ASCs were then differentiated into the three lineages, using established protocols, and assessed by RT-PCR and histology at multiple time points. ASC-CSs remained healthy up to 3?weeks of hyperconfluent culture. One week-old cell sheets displayed upregulation of early differentiation gene markers (Runx2 and Sox9); however, subsequent differentiation results indicated that they did not necessarily translate to an improved phenotype. ASCs within the preformed cell sheet groups did not differentiate as efficiently as the non-hyperconfluent ASCs, which were directly differentiated. Although ASCs within the cell sheets retained their differentiation capacity and remained viable under prolonged hyperconfluent conditions, future applications of ASC-CSs in tissue engineering should be considered with care. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23784965

Neo, Puay Yong; See, Eugene Yong-Shun; Toh, Siew Lok; Goh, James Cho-Hong

2013-06-20

234

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

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

Kim, Do Rim; Kim, Ha Young; Park, Jae Kwang; Park, Seong Kyu; Chang, Mun Seog

2013-07-29

235

Direct and indirect effects of microstructured titanium substrates on the induction of mesenchymal stem cell differentiation towards the osteoblast lineage  

Microsoft Academic Search

Microstructured and high surface energy titanium substrates increase osseointegration in vivo. In vitro, osteoblast differentiation is increased, but effects of the surface directly on multipotent mesenchymal stem cells (MSCs) and consequences for MSCs in the peri-implant environment are not known. We evaluated responses of human MSCs to substrate surface properties and examined the underlying mechanisms involved. MSCs exhibited osteoblast characteristics

Rene Olivares-Navarrete; Sharon L. Hyzy; Daphne L. Hutton; Christopher P. Erdman; Marco Wieland; Barbara D. Boyan; Zvi Schwartz

2010-01-01

236

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

237

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.

2013-01-01

238

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

PubMed Central

Umbilical cord blood (UCB) transplantation has emerged as promising therapy, but 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.

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

2012-01-01

239

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

240

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

Microsoft Academic Search

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

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

2009-01-01

241

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

Microsoft Academic Search

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

Xuejun Xin; Mohammad Hussain; Jeremy J. Mao

2007-01-01

242

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

243

The End of the Dinosaurs  

NASA Astrophysics Data System (ADS)

The discovery of the giant Chicxulub impact crater, buried off the coast of Mexico, unveiled the solution to one of Earth's greatest mysteries--what killed the dinosaurs. Scientists uncovered physical evidence to explain the mass extinction that rocked the Earth 65 million years ago. Step-by-step, The End of the Dinosaurs: Chicxulub Crater and Mass Extinctions tells this great scientific detective story. Charles Frankel recounts the birth of the cosmic hypothesis, which holds that the crash of a meteor on the Earth's surface killed two-thirds of life and all the dinosaurs. He first provides a dramatic account of the impact and its aftermath. Frankel then goes on to detail the controversy that preceded the acceptance of the cosmic hypothesis, the search for the crater, its discovery and ongoing exploration, and the effect of the giant impact on the biosphere. In addition, he reviews other mass extinctions in the fossil record and the threat of asteroids and comets to our planet today. More than 70 photographs and diagrams enhance and help illustrate the material. Filled with drama and interesting science, The End of the Dinosaurs will readily appeal to both the general reader fascinated with the subject and the specialist always searching for more clues to this great mystery. Charles Frankel has written a number of articles on the earth sciences in books and magazines. His many books include Volcanoes of the Solar System (Cambridge University Press 1996).

Frankel, Charles

1999-10-01

244

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

245

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.

246

ER Stress Activating ATF4/CHOP-TNF-? Signaling Pathway Contributes to Alcohol-Induced Disruption of Osteogenic Lineage of Multipotential Mesenchymal Stem Cell.  

PubMed

Background/Aims: Studies have provided substantial evidence that osteoblasts and adipocytes share common progenitor?multipotential mesenchymal stem cells in bone marrow (BMSCs), and excessive alcohol consumption shifts away from osteogenic to adipogenic lineage. However, how exactly alcohol impairs osteogenesis is still incompletely understood. This study was designed to shed light on this issue. Methods: We treated primary BMSCs from human subjects with alcohol for 24 days. We measured changes of genes related to endoplasmic reticulum (ER) stress, adipogenic markers and osteogenic markers using quantitative real-time RT-PCR and Western blot analysis. We performed Oil red O staining and quantification of adipogenesis. We also conducted caspase 3 activity assay to assess BMSC apoptosis. Results: We showed here that chronic exposure of BMSCs to alcohol induced adipogenesis and disrupted osteogenesis as indicated by upregulation of adipogenic markers (PPAR?2 and aP2), downregulation of osteogenic markers (Osf2/Cbfa1), and accumulation of lipid droplets. Alcohol induced ER stress, as reflected by increased expression of glucose-regulated proteins GRP78 and GRP94, and by increased expression of transcription factors activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP), and enhanced caspase 3 activity. Additionally, ER stress also upregulated tumor necrosis factor-alpha (TNF-?). Simultaneous silencing of ATF4 and CHOP prevented upregulation of TNF-?. Knockdown of either ATF4 and CHOP or TNF-? by their siRNAs was able to reverse the ethanol-induced adipogenesis. Conclusion: Our data therefore revealed a role of ER stress and ATF4/CHOP in the ethanol-induced inhibition of osteogenesis, and activation of TNF-? signaling by ATF4/CHOP linking ER stress to adipogenic lineage in response to alcohol stimulation. This work should establish a new signaling pathway linking alcohol, ER stress, and TNF-? to loss of bone formation: Ethanol ? ER stress??? ? ATF4 & CHOP??? ? TNF-???? ? Osteoblasts???. © 2013 S. Karger AG, Basel. PMID:24080827

Chen, Yueping; Gao, Hui; Yin, Qingshui; Chen, Liang; Dong, Panfeng; Zhang, Xiaoyun; Kang, Jie

2013-09-13

247

Effect of enamel matrix derivative and of proline-rich synthetic peptides on the differentiation of human mesenchymal stem cells toward the osteogenic lineage.  

PubMed

With the aim of discovering new molecules for induction of bone formation and biomineralization, combination of bioinformatics and simulation methods were used to design the structure of artificial peptides based on proline-rich domains of enamel matrix proteins. In this study, the effect of such peptides on the differentiation toward the osteogenic lineage of human umbilical cord mesenchymal stem cells (hUCMSCs) was evaluated with or without osteogenic supplements (hydrocortisone, ?-glycerol phosphate, and ascorbic acid) and compared to the effect of the commercially available enamel matrix derivative (EMD). It was hypothesized that the differentiation toward the osteogenic lineage of hUCMSCs would be promoted by the treatment with the synthetic peptides when combined with differentiation media, or it could even be directed exclusively by the synthetic peptides. Osteoinductivity was assessed by cell proliferation, bone morphogenetic protein-2 secretion, and gene expression of osteogenic markers after 1, 3, and 14 days of treatment. All peptides were safe with the dosages used, showing lower cell toxicity. P2, P4, and P6 reduced cell proliferation with growing media by 10%-15%. Higher expression of early osteoblast markers was found after 3 days of treatment with EMD in combination with osteogenic supplements, while after 14 days of treatment, cells treated by the different synthetic peptides in combination with osteogenic supplements showed higher osteocalcin mRNA levels. We can conclude that osteogenic differentiation of hUCMSCs is promoted by short-term EMD treatment in combination with osteogenic supplements and by long-term treatment by the synthetic peptides in combination with osteogenic supplements, showing similar results for all the peptide variants analyzed in this study. PMID:22429009

Ramis, Joana Maria; Rubert, Marina; Vondrasek, Jiri; Gayà, Antoni; Lyngstadaas, Staale Petter; Monjo, Marta

2012-03-19

248

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

PubMed

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; Raghavachari, Nalini

2011-08-09

249

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.

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

2011-01-01

250

Direct and Indirect Effects of Microstructured Titanium Substrates on the Induction of Mesenchymal Stem Cell Differentiation towards the Osteoblast Lineage  

PubMed Central

Microstructured and high surface energy titanium substrates increase osseointegration in vivo. In vitro, osteoblast differentiation is increased, but effects of the surface directly on multipotent mesenchymal stem cells (MSCs) and consequences for MSCs in the peri-implant environment are not known. We evaluated responses of human MSCs to substrate surface properties and examined the underlying mechanisms involved. MSCs exhibited osteoblast characteristics (alkaline phosphatase, RUNX2, and osteocalcin) when grown on microstructured Ti; this effect was more robust with increased hydrophilicity. Factors produced by osteoblasts grown on microstructured Ti were sufficient to induce co-cultured MSC differentiation to osteoblasts. Silencing studies showed that this was due to signaling via ?2?1 integrins in osteoblasts on the substrate surface and paracrine action of secreted Dkk2. Thus, human MSCs are sensitive to substrate properties that induce osteoblastic differentiation; osteoblasts interact with these surface properties via ?2?1 and secrete Dkk2, which acts on distal MSCs.

Olivares-Navarrete, Rene; Hyzy, Sharon; Hutton, Daphne; Erdman, Christopher; Wieland, Marco; Boyan, Barbara D.; Schwartz, Zvi

2010-01-01

251

Direct and indirect effects of microstructured titanium substrates on the induction of mesenchymal stem cell differentiation towards the osteoblast lineage.  

PubMed

Microstructured and high surface energy titanium substrates increase osseointegration in vivo. In vitro, osteoblast differentiation is increased, but effects of the surface directly on multipotent mesenchymal stem cells (MSCs) and consequences for MSCs in the peri-implant environment are not known. We evaluated responses of human MSCs to substrate surface properties and examined the underlying mechanisms involved. MSCs exhibited osteoblast characteristics (alkaline phosphatase, RUNX2, and osteocalcin) when grown on microstructured Ti; this effect was more robust with increased hydrophilicity. Factors produced by osteoblasts grown on microstructured Ti were sufficient to induce co-cultured MSC differentiation to osteoblasts. Silencing studies showed that this was due to signaling via alpha2beta1 integrins in osteoblasts on the substrate surface and paracrine action of secreted Dkk2. Thus, human MSCs are sensitive to substrate properties that induce osteoblastic differentiation; osteoblasts interact with these surface properties via alpha2beta1 and secrete Dkk2, which acts on distal MSCs. PMID:20053436

Olivares-Navarrete, Rene; Hyzy, Sharon L; Hutton, Daphne L; Erdman, Christopher P; Wieland, Marco; Boyan, Barbara D; Schwartz, Zvi

2010-01-06

252

Inherent propensity of amnion-derived mesenchymal stem cells towards endothelial lineage: vascularization from an avascular tissue.  

PubMed

One of the most pressing problems in injury is wound healing and blood vessel formation. The amniotic membrane is important in clinical applications as it is pro-angiogenic, anti-fibrotic and anti-scarring and has low immunogenicity. In this study, we characterized amniotic membrane mesenchymal stem cells (AMMSCs) by their trademark mesenchymal stem cell (MSC) signature and profiled for embryonic pluripotency markers namely alkaline phosphatase, Oct4, Sox2, Nanog, SSEA3 and 4, and Klf4 by RT-PCR and nuclear localization of Oct4 and Nanog by immunocytochemistry. The amnion, although avascular, contains pro-angiogenic factors such as type I, III, IV and V collagen, laminin, and fibronectin in the extra cellular matrix. We, therefore, hypothesized that AMMSCs is pro-angiogenic. Thus, we demonstrate that MSCs derived from the amnion have a natural ability to initiate endothelialization and angiogenesis in vitro. Our results using a wound scratch assay and angiogenesis on Matrigel suggest a pro-angiogenic property of AMMSCs. We also show that native, uninduced AMMSCs are able to form endothelial rings in Matrigel. Further evidence was provided by RT-PCR showing the expression of pro-angiogenic factors such as Tie2, Ang1, VEGF, VEGFR, vWF, KDR and Flt4 in native AMMSCs. Taken together, our results suggest that MSCs from an avascular amnion have an inherent propensity for promoting angiogenesis and could be an ideal choice in wound healing, stroke and ischemic diseases that require rapid vascularization and tissue restoration. PMID:22840296

Warrier, S; Haridas, N; Bhonde, R

2012-07-25

253

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

254

Dino Might: Who Was the Strongest Dinosaur?  

NSDL National Science Digital Library

In this lesson, students will investigate the idea of strength in dinosaurs, and decide for themselves which was the strongest. Background materials point out the difficulty in determining the strength of a dinosaur from fossilized remains, and that size may not be a good measure of strength. The students will review the background material and other printed and online resources, then write an essay supporting their choices for the strongest (or most ferocious) dinosaur. A downloadable, printable version is included.

255

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

2012-05-14

256

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

257

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.

258

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.

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

259

The Four-Winged Dinosaur  

NSDL National Science Digital Library

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

Dunn, Tasha

260

Quantitative CT of dinosaur bones.  

PubMed

To develop a protocol for CT examinations of fossilized saurian bones and to provide paleontologists with morphometric and densitometric data suitable for functional analysis, four isolated long bones of Tendaguru dinosaurs from the Museum for Natural Sciences of the Humboldt University of Berlin were examined by CT. The demonstration of fossils in the axial CT proved optimal with the window set at a center of 2,640 Hounsfield units (HU) and a width of 1,040 HU. The petrified bones have a maximum density of 3,000 HU. The shape and structure of the skeletal remnants suggest that the extremities of Tendaguru dinosaurs were submitted to mainly compression but nearly no bending stress. PMID:12439322

Golder, Werner; Christian, Andreas

261

Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda)  

PubMed Central

Living archosaurs comprise birds (dinosaurs) and crocodylians (suchians). The morphological diversity of birds and stem group dinosaurs is tremendous and well-documented. Suchia, the archosaurian group including crocodylians, is generally considered more conservative. Here, we report a new Late Triassic suchian archosaur with unusual, highly specialized features that are convergent with ornithomimid dinosaurs. Several derived features of the skull and postcranial skeleton are identical to conditions in ornithomimids. Such cases of extreme convergence in multiple regions of the skeleton in two distantly related vertebrate taxa are rare. This suggests that these archosaurs show iterative patterns of morphological evolution. It also suggests that this group of suchians occupied the adaptive zone that was occupied by ornithomimosaurs later in the Mesozoic.

Nesbitt, Sterling J; Norell, Mark A

2006-01-01

262

Cell lineage and regional identity of cultured spinal cord neural stem cells and comparison to brain-derived neural stem cells.  

PubMed

Neural stem cells (NSCs) can be isolated from different regions of the central nervous system. There has been controversy whether regional differences amongst stem and progenitor cells are cell intrinsic and whether these differences are maintained during expansion in culture. The identification of inherent regional differences has important implications for the use of these cells in neural repair. Here, we compared NSCs derived from the spinal cord and embryonic cortex. We found that while cultured cortical and spinal cord derived NSCs respond similarly to mitogens and are equally neuronogenic, they retain and maintain through multiple passages gene expression patterns indicative of the region from which they were isolated (e.g Emx2 and HoxD10). Further microarray analysis identified 229 genes that were differentially expressed between cortical and spinal cord derived neurospheres, including many Hox genes, Nuclear receptors, Irx3, Pace4, Lhx2, Emx2 and Ntrk2. NSCs in the cortex express LeX. However, in the embryonic spinal cord there are two lineally related populations of NSCs: one that expresses LeX and one that does not. The LeX negative population contains few markers of regional identity but is able to generate LeX expressing NSCs that express markers of regional identity. LeX positive cells do not give rise to LeX-negative NSCs. These results demonstrate that while both embryonic cortical and spinal cord NSCs have similar self-renewal properties and multipotency, they retain aspects of regional identity, even when passaged long-term in vitro. Furthermore, there is a population of a LeX negative NSC that is present in neurospheres derived from the embryonic spinal cord but not the cortex. PMID:19148290

Kelly, Theresa K; Karsten, Stanislav L; Geschwind, Daniel H; Kornblum, Harley I

2009-01-16

263

Dinosaur Remains Found in Oregon  

NSDL National Science Digital Library

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

264

First ceratosaurian dinosaur from Australia.  

PubMed

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. PMID:22552426

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

2012-05-03

265

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

266

Embryonic Skulls of Titanosaur Sauropod Dinosaurs  

Microsoft Academic Search

Little is known about the cranial anatomy of the taxonomically diverse and geographically widespread titanosaurs, a paucity that has hindered inferences about the genealogical history and evolutionary development of the latest sauropod dinosaurs. Newly discovered fossil eggs containing embryonic remains from the Late Cretaceous of Argentina provide the first articulated skulls of titanosaur dinosaurs. The nearly complete fetal skulls shed

Luis M. Chiappe; Leonardo Salgado; Rodolfo A. Coria

2001-01-01

267

New Insights Into Dinosaur Jaw Muscle Anatomy  

Microsoft Academic Search

Jaw muscles are key components of the head and critical to testing hypotheses of soft-tissue homology, skull function, and evolution. Dinosaurs evolved an extraordinary diversity of cranial forms adapted to a variety of feeding behaviors. However, disparate evolutionary transformations in head shape and function among dinosaurs and their living relatives, birds and croc- odylians, impair straightforward reconstructions of muscles, and

Casey M. Holliday

2009-01-01

268

Feather Quill Knobs in the Dinosaur Velociraptor  

Microsoft Academic Search

Some nonavian theropod dinosaurs were at least partially covered in feathers or filamentous protofeathers. However, a complete understanding of feather distribution among theropod dinosaurs is limited because feathers are typically preserved only in lagerstätten like that of Solnhofen, Germany or Liaoning, China. Such deposits possess clear taxonomic biases toward small-bodied animals, limiting our knowledge regarding feather presence in larger members

Alan H. Turner; Peter J. Makovicky; Mark A. Norell

2007-01-01

269

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.

O'Gorman, Eoin J.; Hone, David W. E.

2012-01-01

270

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.

Hutchinson, John

271

Compartmental Hollow Fiber Capillary Membrane-Based Bioreactor Technology for In Vitro Studies on Red Blood Cell Lineage Direction of Hematopoietic Stem Cells  

PubMed Central

Continuous production of red blood cells (RBCs) in an automated closed culture system using hematopoietic stem cell (HSC) progenitor cell populations is of interest for clinical application because of the high demand for blood transfusions. Previously, we introduced a four-compartment bioreactor that consisted of two bundles of hollow fiber microfiltration membranes for transport of culture medium (forming two medium compartments), interwoven with one bundle of hollow fiber membranes for transport of oxygen (O2), carbon dioxide (CO2), and other gases (forming one gas compartment). Small-scale prototypes were developed of the three-dimensional (3D) perfusion cell culture systems, which enable convection-based mass transfer and integral oxygenation in the cell compartment. CD34+ HSC were isolated from human cord blood units using a magnetic separation procedure. Cells were inoculated into 2- or 8-mL scaled-down versions of the previously designed 800-mL cell compartment devices and perfused with erythrocyte proliferation and differentiation medium. First, using the small-scale 2-mL analytical scale bioreactor, with an initial seeding density of 800,000 cells/mL, we demonstrated approximately 100-fold cell expansion and differentiation after 7 days of culture. An 8-mL laboratory-scale bioreactor was then used to show pseudocontinuous production by intermediately harvesting cells. Subsequently, we were able to use a model to demonstrate semicontinuous production with up to 14,288-fold expansion using seeding densities of 800,000 cells/mL. The down-scaled culture technology allows for expansion of CD34+ cells and stimulating these progenitors towards RBC lineage, expressing approximately 40% CD235+ and enucleation. The 3D perfusion technology provides an innovative tool for studies on RBC production, which is scalable.

Housler, Greggory J.; Miki, Toshio; Schmelzer, Eva; Pekor, Christopher; Zhang, Xiaokui; Kang, Lin; Voskinarian-Berse, Vanessa; Abbot, Stewart; Zeilinger, Katrin

2012-01-01

272

Conditional induction of Math1 specifies embryonic stem cells to cerebellar granule neuron lineage and promotes differentiation into mature granule neurons.  

PubMed

Directing differentiation of embryonic stem cells (ESCs) to specific neuronal subtype is critical for modeling disease pathology in vitro. An attractive means of action would be to combine regulatory differentiation factors and extrinsic inductive signals added to the culture medium. In this study, we have generated mature cerebellar granule neurons by combining a temporally controlled transient expression of Math1, a master gene in granule neuron differentiation, with inductive extrinsic factors involved in cerebellar development. Using a Tetracyclin-On transactivation system, we overexpressed Math1 at various stages of ESCs differentiation and found that the yield of progenitors was considerably increased when Math1 was induced during embryonic body stage. Math1 triggered expression of Mbh1 and Mbh2, two target genes directly involved in granule neuron precursor formation and strong expression of early cerebellar territory markers En1 and NeuroD1. Three weeks after induction, we observed a decrease in the number of glial cells and an increase in that of neurons albeit still immature. Combining Math1 induction with extrinsic factors specifically increased the number of neurons that expressed Pde1c, Zic1, and GABA?6R characteristic of mature granule neurons, formed "T-shaped" axons typical of granule neurons, and generated synaptic contacts and action potentials in vitro. Finally, in vivo implantation of Math1-induced progenitors into young adult mice resulted in cell migration and settling of newly generated neurons in the cerebellum. These results show that conditional induction of Math1 drives ESCs toward the cerebellar fate and indicate that acting on both intrinsic and extrinsic factors is a powerful means to modulate ESCs differentiation and maturation into a specific neuronal lineage. PMID:23225629

Srivastava, Rupali; Kumar, Manoj; Peineau, Stéphane; Csaba, Zsolt; Mani, Shyamala; Gressens, Pierre; El Ghouzzi, Vincent

2013-04-01

273

Dynamic Locomotor Capabilities Revealed by Early Dinosaur Trackmakers from Southern Africa  

PubMed Central

Background A new investigation of the sedimentology and ichnology of the Early Jurassic Moyeni tracksite in Lesotho, southern Africa has yielded new insights into the behavior and locomotor dynamics of early dinosaurs. Methodology/Principal Findings The tracksite is an ancient point bar preserving a heterogeneous substrate of varied consistency and inclination that includes a ripple-marked riverbed, a bar slope, and a stable algal-matted bar top surface. Several basal ornithischian dinosaurs and a single theropod dinosaur crossed its surface within days or perhaps weeks of one another, but responded to substrate heterogeneity differently. Whereas the theropod trackmaker accommodated sloping and slippery surfaces by gripping the substrate with its pedal claws, the basal ornithischian trackmakers adjusted to the terrain by changing between quadrupedal and bipedal stance, wide and narrow gauge limb support (abduction range?=?31°), and plantigrade and digitigrade foot posture. Conclusions/Significance The locomotor adjustments coincide with changes in substrate consistency along the trackway and appear to reflect ‘real time’ responses to a complex terrain. It is proposed that these responses foreshadow important locomotor transformations characterizing the later evolution of the two main dinosaur lineages. Ornithischians, which shifted from bipedal to quadrupedal posture at least three times in their evolutionary history, are shown to have been capable of adopting both postures early in their evolutionary history. The substrate-gripping behavior demonstrated by the early theropod, in turn, is consistent with the hypothesized function of pedal claws in bird ancestors.

Wilson, Jeffrey A.; Marsicano, Claudia A.; Smith, Roger M. H.

2009-01-01

274

Advances in cell lineage reprogramming.  

PubMed

As a milestone breakthrough of stem cell and regenerative medicine in recent years, somatic cell reprogramming has opened up new applications of regenerative medicine by breaking through the ethical shackles of embryonic stem cells. However, induced pluripotent stem (iPS) cells are prepared with a complicated protocol that results in a low reprogramming rate. To obtain differentiated target cells, iPS cells and embryonic stem cells still need to be induced using step-by-step procedures. The safety of induced target cells from iPS cells is currently a further concerning matter. More broadly conceived is lineage reprogramming that has been investigated since 1987. Adult stem cell plasticity, which triggered interest in stem cell research at the end of the last century, can also be included in the scope of lineage reprogramming. With the promotion of iPS cell research, lineage reprogramming is now considered as one of the most promising fields in regenerative medicine, will hopefully lead to customized, personalized therapeutic options for patients in the future. PMID:23526388

Zhou, Junnian; Yue, Wen; Pei, Xuetao

2013-03-23

275

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

276

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...

277

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

Microsoft Academic Search

A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern\\u000a Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous–Tertiary mass extinction\\u000a event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest\\u000a Cretaceous dinosaur taxa could reproduce in polar region and were

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

2009-01-01

278

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

279

Understanding cell lineages as complex adaptive systems.  

PubMed

Stem cells may be considered complex reactive systems because of their vast number in a living system, their reactive nature, and the influence of local environmental factors (such as the state of neighboring cells, tissue matrix, stem cell physiological processes) on their behavior. In such systems, emergent global behavior arises through the multitude of local interactions among the cell agents. Approaching hematopoietic and other stem cell lineages from this perspective have critical ramifications on current thinking relating to the plasticity of these lineage systems, the modeling of stem cell systems, and the interpretation of clinical data regarding many diseases within such models. PMID:14757407

Theise, Neil D; d'Inverno, Mark

280

Cord Blood-Derived Macrophage-Lineage Cells Rapidly Stimulate Osteoblastic Maturation in Mesenchymal Stem Cells in a Glycoprotein-130 Dependent Manner  

PubMed Central

In bone, depletion of osteoclasts reduces bone formation in vivo, as does osteal macrophage depletion. How osteoclasts and macrophages promote the action of bone forming osteoblasts is, however, unclear. Since recruitment and differentiation of multi-potential stromal cells/mesenchymal stem cells (MSC) generates new active osteoblasts, we investigated whether human osteoclasts and macrophages (generated from cord blood-derived hematopoietic progenitors) induce osteoblastic maturation in adipose tissue-derived MSC. When treated with an osteogenic stimulus (ascorbate, dexamethasone and ?-glycerophosphate) these MSC form matrix-mineralising, alkaline phosphatase-expressing osteoblastic cells. Cord blood-derived progenitors were treated with macrophage colony stimulating factor (M-CSF) to form immature proliferating macrophages, or with M-CSF plus receptor activator of NF?B ligand (RANKL) to form osteoclasts; culture medium was conditioned for 3 days by these cells to study their production of osteoblastic factors. Both osteoclast- and macrophage-conditioned medium (CM) greatly enhanced MSC osteoblastic differentiation in both the presence and absence of osteogenic medium, evident by increased alkaline phosphatase levels within 4 days and increased mineralisation within 14 days. These CM effects were completely ablated by antibodies blocking gp130 or oncostatin M (OSM), and OSM was detectable in both CM. Recombinant OSM very potently stimulated osteoblastic maturation of these MSC and enhanced bone morphogenetic protein-2 (BMP-2) actions on MSC. To determine the influence of macrophage activation on this OSM-dependent activity, CM was collected from macrophage populations treated with M-CSF plus IL-4 (to induce alternative activation) or with GM-CSF, IFN? and LPS to cause classical activation. CM from IL-4 treated macrophages stimulated osteoblastic maturation in MSC, while CM from classically-activated macrophages did not. Thus, macrophage-lineage cells, including osteoclasts but not classically activated macrophages, can strongly drive MSC-osteoblastic commitment in OSM-dependent manner. This supports the notion that eliciting gp130-dependent signals in human MSC would be a useful approach to increase bone formation.

Fernandes, Tania J.; Hodge, Jason M.; Singh, Preetinder P.; Eeles, Damien G.; Collier, Fiona M.; Holten, Ian; Ebeling, Peter R.

2013-01-01

281

Biology of the sauropod dinosaurs: the evolution of gigantism  

PubMed Central

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

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

2011-01-01

282

Biology of the sauropod dinosaurs: the evolution of gigantism.  

PubMed

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

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

2011-02-01

283

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.

Foundation, Wgbh E.

2005-12-17

284

Are You Smarter Than a Dinosaur?  

NSDL National Science Digital Library

Students investigate the intelligence of dinosaurs by comparing the relative size of brain and body mass to living animals. Students plot the living animals to determine a general relationship of brain and body mass and then use that relation to interpret a range of dinosaurs. The activity gives students practice in graphical data comparison and other methods of data analysis. Students also investigate how well this method works and what weaknesses it might have.

Farley, Martin B.

285

First Dinosaur Tracks from the Arabian Peninsula  

Microsoft Academic Search

BackgroundThe 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

Anne S. Schulp; Mohammed Al-Wosabi; Nancy J. Stevens; Anna Stepanova

2008-01-01

286

Dinosaur extinction: closing the '3 m gap'  

PubMed Central

Modern debate regarding the extinction of non-avian dinosaurs was ignited by the publication of the Cretaceous–Tertiary (K–T) asteroid impact theory and has seen 30 years of dispute over the position of the stratigraphically youngest in situ dinosaur. A zone devoid of dinosaur fossils reported from the last 3 m of the Upper Cretaceous, coined the ‘3 m gap’, has helped drive controversy. Here, we report the discovery of the stratigraphically youngest in situ dinosaur specimen: a ceratopsian brow horn found in a poorly rooted, silty, mudstone floodplain deposit located no more than 13 cm below the palynologically defined boundary. The K–T boundary is identified using three criteria: (i) decrease in Cretaceous palynomorphs without subsequent recovery, (ii) the existence of a ‘fern spike’, and (iii) correlation to a nearby stratigraphic section where primary extraterrestrial impact markers are present (e.g. iridium anomaly, spherules, shocked quartz). The in situ specimen demonstrates that a gap devoid of non-avian dinosaur fossils does not exist and is inconsistent with the hypothesis that non-avian dinosaurs were extinct prior to the K–T boundary impact event.

Lyson, Tyler R.; Bercovici, Antoine; Chester, Stephen G. B.; Sargis, Eric J.; Pearson, Dean; Joyce, Walter G.

2011-01-01

287

Fossils 1: Fossils and Dinosaurs  

NSDL National Science Digital Library

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

288

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

289

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

290

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

291

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

292

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.

VanBuren, Collin S.; Bonnan, Matthew

2013-01-01

293

Forearm posture and mobility in quadrupedal dinosaurs.  

PubMed

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

2013-09-18

294

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

295

Plumage color patterns of an extinct dinosaur.  

PubMed

For as long as dinosaurs have been known to exist, there has been speculation about their appearance. Fossil feathers can preserve the morphology of color-imparting melanosomes, which allow color patterns in feathered dinosaurs to be reconstructed. Here, we have mapped feather color patterns in a Late Jurassic basal paravian theropod dinosaur. Quantitative comparisons with melanosome shape and density in extant feathers indicate that the body was gray and dark and the face had rufous speckles. The crown was rufous, and the long limb feathers were white with distal black spangles. The evolution of melanin-based within-feather pigmentation patterns may coincide with that of elongate pennaceous feathers in the common ancestor of Maniraptora, before active powered flight. Feathers may thus have played a role in sexual selection or other communication. PMID:20133521

Li, Quanguo; Gao, Ke-Qin; Vinther, Jakob; Shawkey, Matthew D; Clarke, Julia A; D'Alba, Liliana; Meng, Qingjin; Briggs, Derek E G; Prum, Richard O

2010-02-04

296

Control of a robot dinosaur  

PubMed Central

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

Papantoniou, V.

1999-01-01

297

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

Federal Register 2010, 2011, 2012, 2013

...Department of the Interior, National Park Service, Dinosaur National Monument, Dinosaur, CO AGENCY: National Park Service, Interior...Department of the Interior, National Park Service, Dinosaur National Monument, Dinosaur, CO, has...

2011-02-09

298

Analysis of dinosaur samples by nuclear microscopy  

NASA Astrophysics Data System (ADS)

Several dinosaur bone and eggshell fossil samples unearthed at different sites in China were analyzed by means of nuclear microscopy. Concentrations and distributions of elements such as Na, Mg, Al, P, S, Ca, Cr, Mn, Fe, Cu, Zn, As, Br, Sr, Y, Ce, Pb and U, etc. were obtained for each sample. The results of quantitative PIXE and RBS analyses show unusually high concentrations of U and Ce in several samples obtained from a period near the K-T boundary (between Cretaceous and Tertiary periods, 65 million years ago), suggesting that some form of environmental pollution could be the cause of dinosaur extinction.

Orli?, I.; Tang, S. M.; Wu, X.; Wang, Y.; Wang, X.; Zhu, J.

1997-07-01

299

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 Âmissing linkÂ. Essentially, this Âlink 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 Âsickle-maker from UtahÂ, largely due to its claws. The results of this important find were documented in this ThursdayÂs 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 ÂItÂs 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.ÂThe first link leads to an article from this WednesdayÂs 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 GeographicÂs website that provides a good perspective on this important discovery. The third link offers some informed insights from NatureÂs 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 ÂWhere did dinosaurs live? and ÂDid dinosaurs communicate?Â. 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.

300

Willo: The Dinosaur with a Heart  

NSDL National Science Digital Library

This site refers to the discovery of a fossilized dinosaur heart that was reported in the April 21, 2000 issue of the Journal Science. This heart of a small herbivore called a Thescelosaurus reveals a structure "more like that of a bird or a mammal than those of reptiles, adding substantially to evidence suggesting that at least some dinosaurs had high metabolic rates." The site, from the Center for the Exploration of the Dinosaurian World, a collaboration between North Carolina State University and the North Carolina Museum of Natural Sciences, offers up-to-date information about and images of the important discovery.

301

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

USGS Publications Warehouse

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

Modreski, P. J.

2001-01-01

302

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.

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

2013-01-01

303

What lies beneath: sub-articular long bone shape scaling in eutherian mammals and saurischian dinosaurs suggests different locomotor adaptations for gigantism.  

PubMed

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

2013-10-09

304

Lineage-specific growth factors can compensate for stem and progenitor cell deficiencies at the postprogenitor cell level: an analysis of doubly TPO- and G-CSF receptor-deficient mice.  

PubMed

Multiple lines of evidence indicate that thrombopoietin (TPO) substantially impacts the number of hematopoietic stem cells and progenitors of all myeloid lineages. Nevertheless, tpo knock-out mice (T(-)) display thrombocytopenia only; blood erythroid and neutrophil levels are normal despite 60% to 85% reductions in stem and progenitor cells. The compensatory mechanism(s) for these deficiencies remains uncertain; lineage-specific cytokines such as erythropoietin or granulocyte colony-stimulating factor (G-CSF) have been postulated but never proven to be responsible. To directly test whether G-CSF can compensate for the myeloid progenitor cell reduction in the T(-) model of hematopoietic deficiency, T(-) and G-CSF-receptor knock-out (GR(-)) mice were crossed, and F1 animals bred to obtain doubly nullizygous mice (T(-)GR(-)). This experiment also allowed us to test the hypothesis that G-CSF contributes to the residual platelet production in T(-) mice. We found that T(-)GR(-) F2 mice displayed similar blood platelet levels as that seen in T(-) mice, indicating that G-CSF does not account for the residual megakaryopoiesis in T(-) mice. However, we also noted excessive perinatal mortality of T(-)GR(-) animals, caused by infection due to a profound and significant decrease in marrow and peripheral blood neutrophils, far greater than that seen in either T(-) or GR(-) mice. These data indicate that in the additional absence of GR, T(-) mice cannot compensate for their 62% reduction in myeloid progenitors and become profoundly neutropenic, supporting the hypothesis that G-CSF can compensate for the myeloid effects of TPO deficiency by expanding the pool of cells between the granulocyte-macrophage colony-forming unit and mature neutrophil stages of granulopoiesis. PMID:11986210

Kaushansky, Kenneth; Fox, Norma; Lin, Nancy L; Liles, W Conrad

2002-05-15

305

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

306

Two feathered dinosaurs from northeastern China  

Microsoft Academic Search

Current controversy over the origin and early evolution of birds centres on whether or not they are derived from coelurosaurian theropod dinosaurs. Here we describe two theropods from the Upper Jurassic\\/Lower Cretaceous Chaomidianzi Formation of Liaoning province, China. Although both theropods have feathers, it is likely that neither was able to fly. Phylogenetic analysis indicates that they are both more

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

1998-01-01

307

Phylogeny and Historical Biogeography of Hadrosaurid Dinosaurs  

Microsoft Academic Search

Hadrosaurids were the most diverse and abundant dinosaurs at the end of the Cretaceous. However, their phylogeny is incompletely known and the relationships of many taxa, particularly European and South American, remains unresolved. Questions remain regarding the timing of their origin and which attributes might have allowed these animals to diversify and colonize nearly all continents by the late Campanian.

Albert Prieto-Marquez

2008-01-01

308

Dinosaur diversity and the rock record  

PubMed Central

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.

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

2009-01-01

309

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.

310

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.

311

A beaver buddy for the dinosaurs?  

NSDL National Science Digital Library

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

American Association for the Advancement of Science (AAAS;)

2006-02-23

312

Theory Choices: What Happened to the Dinosaurs?  

NSDL National Science Digital Library

In this lesson, students read and discuss articles presenting two alternative theories about the extinction of dinosaurs. They are encouraged to use the criteria that scientists use to get the best solution. Students will learn that: some evolutionary change is rapid and discontinuous; extinction plays in role in macroevolution; and scientists use specific criteria in deciding which theory is better.

313

Large Mesozoic mammals fed on young dinosaurs  

Microsoft Academic Search

Mesozoic mammals are commonly portrayed as shrew- or rat-sized animals that were mainly insectivorous, probably nocturnal and lived in the shadow of dinosaurs. The largest known Mesozoic mammal represented by substantially complete remains is Repenomamus robustus, a triconodont mammal from the Lower Cretaceous of Liaoning, China. An adult individual of R. robustus was the size of a Virginia opossum. Here

Yaoming Hu; Jin Meng; Yuanqing Wang; Chuankui Li

2005-01-01

314

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

2009-04-29

315

Dinosaur origins: evidence from the footprint record  

Microsoft Academic Search

Triassic tracks and trackways assigned to dinosaur trackmakers or closest relatives have been mentioned from several Middle to the latest Triassic successions from both northern and southern Pangea. At present, the earliest gondwanan records are those from the Middle Triassic Los Rastros Formation in west-central Argentina. A reanalysis of Los Rastros ichnites at the Ischichuca area, including new material, has

Claudia A. Marsicano; Nadia S. Domnanovich; Adriana C. Mancuso

2007-01-01

316

Resources and energetics determined dinosaur maximal size  

PubMed Central

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

McNab, Brian K.

2009-01-01

317

Resources and energetics determined dinosaur maximal size.  

PubMed

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

McNab, Brian K

2009-07-06

318

A subpopulation of mouse esophageal basal cells has properties of stem cells with the capacity for self-renewal and lineage specification.  

PubMed

The esophageal epithelium is a prototypical stratified squamous epithelium that exhibits an exquisite equilibrium between proliferation and differentiation. After basal cells proliferate, they migrate outward toward the luminal surface, undergo differentiation, and eventually slough due to apoptosis. The identification and characterization of stem cells responsible for the maintenance of the esophageal epithelium remains elusive. Here, we employed Hoechst dye extrusion and BrdU label-retaining assays to identify in mice a potential esophageal stem cell population that localizes to the basal cell compartment. The self-renewing capacity of this population was characterized using a clonogenic assay and a 3D organotypic culture model. The putative esophageal stem cells were also capable of epithelial reconstitution in vivo in direct esophageal epithelial injury models. In both the 3D organotypic culture and direct mucosal injury models, the putative stem cells gave rise to undifferentiated and differentiated cells. These studies therefore provide a basis for understanding the regenerative capacity and biology of the esophageal epithelium when it is faced with injurious insults. PMID:19033657

Kalabis, Jiri; Oyama, Kenji; Okawa, Takaomi; Nakagawa, Hiroshi; Michaylira, Carmen Z; Stairs, Douglas B; Figueiredo, Jose-Luiz; Mahmood, Umar; Diehl, J Alan; Herlyn, Meenhard; Rustgi, Anil K

2008-11-06

319

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

320

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.

321

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

322

Cyclopamine treatment of human embryonic stem cells followed by culture in human astrocyte medium promotes differentiation into nestin- and GFAP-expressing astrocytic lineage  

Microsoft Academic Search

Human embryonic stem cells (hESCs) are able to differentiate into various cell types, including neuronal cells and glial cells. However, little information is available regarding astrocyte differentiation. This report describes the differentiation of hESCs into nestin- and GFAP-expressing astrocytes following treatment with cyclopamine, which is an inhibitor of Hedgehog (Hh) signaling, and culturing in human astrocyte medium (HAM). In hESCs,

Dong-Seok Lee; Kweon Yu; Jeung-Yon Rho; Eunyoung Lee; Jee-Soo Han; Deog-Bon Koo; Yee Sook Cho; Janghwan Kim; Kyung-Kwang Lee; Yong-Mahn Han

2006-01-01

323

The Genetic Engineering of Hematopoietic Stem Cells: the Rise of Lentiviral Vectors, the Conundrum of the LTR, and the Promise of Lineage-restricted Vectors  

Microsoft Academic Search

Recent studies on the integration patterns of different categories of retroviral vectors, the genotoxicity of long-terminal repeats (LTRs) and other genetic elements, the rise of lentiviral technology and the emergence of regulated vector systems providing tissue-restricted transgene expression and RNA interference, are profoundly changing the landscape of stem cell-based therapies. New developments in vector design and an increasing understanding of

Alex H Chang; Michel Sadelain

2007-01-01

324

Stable-isotope analyses of dinosaur eggshells: Paleoenvironmental implications  

NASA Astrophysics Data System (ADS)

Well-preserved clutches of dinosaur (sauropod) eggshells and skeletal remains have been discovered in the Upper Cretaceous Lameta limestones of the Kheda district, Gujarat, India, indicating a dinosaur nesting site. Oxygen-isotope analyses of the eggs show that the dinosaurs drank from a variety of freshwater bodies such as rivers and small evaporative pools, whereas the carbon-isotope values indicate that the reptiles were consuming plants that utilize the C3 photosynthetic pathway, e.g., small palms, shrubs, conifers, etc. Similar analyses of the host limestones suggest that they were deposited in a freshwater environment that provided the niche for large-scale breeding and nesting of the dinosaurs.

Sarkar, A.; Bhattacharya, S. K.; Mohabey, D. M.

1991-11-01

325

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

2010-07-29

326

Lineage specificity of gene expression patterns  

PubMed Central

The hematopoietic system offers many advantages as a model for understanding general aspects of lineage choice and specification. Using oligonucleotide microarrays, we compared gene expression patterns of multiple purified hematopoietic cell populations, including neutrophils, monocytes, macrophages, resting, centrocytic, and centroblastic B lymphocytes, dendritic cells, and hematopoietic stem cells. Some of these cells were studied under both resting and stimulated conditions. We studied the collective behavior of subsets of genes derived from the Biocarta database of functional pathways, hand-tuned groupings of genes into broad functional categories based on the Gene Ontology database, and the metabolic pathways in the Kyoto Encyclopedia of Genes and Genomes database. Principal component analysis revealed strikingly pervasive differences in relative levels of gene expression among cell lineages that involve most of the subsets examined. These results indicate that many processes in these cells behave differently in different lineages. Much of the variation among lineages was captured by the first few principal components. Principal components biplots were found to provide a convenient visual display of the contributions of the various genes within the subsets in lineage discrimination. Moreover, by applying tree-constructing methodologies borrowed from phylogenetics to the expression data from differentiated cells and stem cells, we reconstructed a tree of relationships that resembled the established hematopoietic program of lineage development. Thus, the mRNA expression data implicitly contained information about developmental relationships among cell types.

Kluger, Yuval; Tuck, David P.; Chang, Joseph T.; Nakayama, Yasuhiro; Poddar, Ranjana; Kohya, Naohiko; Lian, Zheng; Nasr, Abdelhakim Ben; Halaban, H. Ruth; Krause, Diane S.; Zhang, Xueqing; Newburger, Peter E.; Weissman, Sherman M.

2004-01-01

327

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.

Mallon, Jordan C.; Anderson, Jason S.

2013-01-01

328

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

PubMed

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

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

2013-05-01

329

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

330

Ectoderm to Mesoderm Lineage Switching During Axolotl Tail Regeneration  

Microsoft Academic Search

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

Karen Echeverri; Elly M. Tanaka

2002-01-01

331

A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea.  

PubMed

Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and bracket the formation with (40)Ar/(39)Ar ages. Some 230 million years ago in the Late Triassic (mid Carnian), the earliest dinosaurs were the dominant terrestrial carnivores and small herbivores in southwestern Pangaea. The extinction of nondinosaurian herbivores is sequential and is not linked to an increase in dinosaurian diversity, which weakens the predominant scenario for dinosaurian ascendancy as opportunistic replacement. PMID:21233386

Martinez, Ricardo N; Sereno, Paul C; Alcober, Oscar A; Colombi, Carina E; Renne, Paul R; Montañez, Isabel P; Currie, Brian S

2011-01-14

332

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

333

"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…

Herminghaus, Trisha, Ed.

334

Ecological and evolutionary impli- cations of dinosaur feeding behaviour  

Microsoft Academic Search

Dinosaurs had a wide variety of feeding mechanisms that strongly impacted on their ecology and evolution. Here, we show how novel application of technologies borrowed from medicine and engineering, such as CT scanning and Finite Element Analysis, have recently been combined with traditional approaches to result in significant advances in our understanding of dinosaur palaeobiology. Taxon-specific studies are providing quantitative

Paul M. Barrett; Emily J. Rayfield

2006-01-01

335

36 CFR 7.63 - Dinosaur National Monument.  

Code of Federal Regulations, 2010 CFR

...Public Property 1 2010-07-01 2010-07-01 false Dinosaur National Monument. 7.63 Section 7.63 Parks, Forests...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.63 Dinosaur National Monument. (a) Commercial hauling....

2010-07-01

336

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

337

36 CFR 7.63 - Dinosaur National Monument.  

Code of Federal Regulations, 2010 CFR

...Public Property 1 2009-07-01 2009-07-01 false Dinosaur National Monument. 7.63 Section 7.63 Parks, Forests...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.63 Dinosaur National Monument. (a) Commercial hauling....

2009-07-01

338

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

339

The Metabolic Status of Some Late Cretaceous Dinosaurs  

Microsoft Academic Search

Analysis of the nasal region in fossils of three theropod dinosaurs (Nanotyrannus, Ornithomimus, and Dromaeosaurus) and one omithischian dinosaur (Hypacrosaurus) showed that their metabolic rates were significantly lower than metabolic rates in modern birds and mammals. In extant endotherms and ectotherms, the cross-sectional area of the nasal passage scales approximately with increasing body mass M at M0 72. However, the

John A. Ruben; Willem J. Hillenius; Nicholas R. Geist; Andrew Leitch; Terry D. Jones; Philip J. Currie; John R. Horner; George Espe III

1996-01-01

340

An Exercise on Dinosaur Trackways for Introductory Science Courses.  

ERIC Educational Resources Information Center

Presents an exercise in which cutouts or outlines of dinosaur footprints placed independently or in sets on the floor and laboratory benches are used to model dinosaur trackways. The nature, size, speed, and specific behavior of the trackmaker are determined from the trackways and from student-derived data as well as from diagrams and models based…

Over, D. Jeffrey

1995-01-01

341

Use of ground penetrating radar in detecting fossilized dinosaur bones  

Microsoft Academic Search

Ground penetrating radar (GPR) has been used successfully to help archaeologists locate building foundations and other artifacts of past civilizations. Yet, little has been done to help paleontologists in their search for fossilized remains. Fossilized and partially fossilized dinosaur bones are located in a sandstone outcrop at the Dinosaur Ridge Natural Landmark outside Morrison, Colorado. The bones are located within

Todd M. Meglich

2000-01-01

342

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

343

Dinosaurs and fluctuating sea levels during the mesozoic  

Microsoft Academic Search

The very different frequency of dinosaurs during the Mesozoic can be allied to the correlation between global sea level cyclicity and fossilization. This is based upon the sedimentary situation in the inner shelf, the area of predominant fossil record of dinosaurs, and sea level fluctuations. A rich fossil record is found in times of high sea level, and vice versa.

Hartmut Haubold

1990-01-01

344

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

345

Dinosaurs and the island rule: The dwarfed dinosaurs from Ha?eg Island  

Microsoft Academic Search

Islands are fascinating natural laboratories of evolution. One much debated theme among evolutionary ecologists is whether there is an ‘island rule’, the observation that large animals tend to become smaller and small animals larger. Franz Nopcsa was the first, in 1914, to suggest that the latest Cretaceous dinosaurs from Ha?eg, Romania were an island fauna, based on its low diversity

Michael J. Benton; Zoltan Csiki; Dan Grigorescu; Ragna Redelstorff; P. Martin Sander; Koen Stein; David B. Weishampel

2010-01-01

346

A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea  

Microsoft Academic Search

Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and bracket the formation with 40Ar\\/39Ar ages. Some 230 million years ago

Ricardo N. Martinez; Paul C. Sereno; Oscar A. Alcober; Carina E. Colombi; Paul R. Renne; Isabel P. Montañez; Brian S. Currie

2011-01-01

347

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

PubMed Central

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

2013-01-01

348

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

PubMed

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

Maidment, Susannah C R; Barrett, Paul M

2012-06-20

349

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

PubMed Central

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

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

2011-01-01

350

Brain tumor stem cells  

Microsoft Academic Search

The concept of brain tumor stem cells is gaining increased recognition in neuro-oncology. Until recently, the paradigm of\\u000a a tumor-initiating stem cell was confined to hematopoietic malignancies where the hierarchical lineages of stem progenitor\\u000a cells are well established. The demonstration of persistent stem cells and cycling progenitors in the adult brain, coupled\\u000a with the expansion of the cancer stem cell

Georgia Panagiotakos; Viviane Tabar

2007-01-01

351

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.

352

Paleontology. Learning to dissect dinosaurs--digitally.  

PubMed

In the past 2 decades, as the resolution of computed tomography (CT) scans has grown sharper, paleontologists have increasingly trained the technique on long-dead animals, gaining an inside view of rich anatomical detail, including everything from bony canals that once held nerves to the internal networks of dinosaur noses. The technique doesn't work on all samples, and the images still require a trained eye to interpret. But CT scanning has contributed to a number of high-profile discoveries. PMID:10877686

Stokstad, E

2000-06-01

353

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

Microsoft Academic Search

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

Joel Berger; Carol Cunningham

1995-01-01

354

Hadrosaurus foulkii: Finding the World's First Dinosaur Skeleton  

NSDL National Science Digital Library

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

Levins, Hoag

355

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

356

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

357

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

358

An Interdisciplinary Approach to Dinosaur Fossils, Morphology, Ethology, and Energetics.  

ERIC Educational Resources Information Center

|Describes an interdisciplinary minicourse on dinosaur fossils, morphology, ethology, and energetics. Suggests and provides examples of hands-on activities for junior high school- through college-level students. (DS)|

Zipko, Stephen J.

1981-01-01

359

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

360

New discovery on dinosaur fossils from Early Jurassic, Sichuan, China  

Microsoft Academic Search

An early and primitive sauropod dinosaur,Gongxianosaurus shibeiensis (gen. et sp. nov.), from Lower Jurassic Dongyuemiao Member of Ziliujing Formation in Shibei Village, Gongxian County, Sichuan\\u000a Province, China is described, which is among Gongxian dinosaur fossils discovered in 1997. Except for skull incomplete, fossils\\u000a were well-preserved. It has concurrently some features of both sauropod and prosauropds. It is an intermediate type

Yaonan Luo; Changsheng Wang

1999-01-01

361

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

362

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

363

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

NSDL National Science Digital Library

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

Fries-Gaither, Jessica

364

Dinosaurs in the Dark: K-1: Illustrated Book  

NSDL National Science Digital Library

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

Fries-Gaither, Jessica

365

Mesozoic dinosaurs from Brazil and their biogeographic implications.  

PubMed

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

Bittencourt, Jonathas S; Langer, Max C

2011-03-01

366

Leukemia Stem Cells  

Microsoft Academic Search

\\u000a Normal hematopoiesis develops hierarchically from a hematopoietic stem cell, which is defined by both extensive self-renewal\\u000a capacity and multi-lineage potential, i.e. the ability to give rise to fully differentiated cells of all hematopoietic lineages.\\u000a Since leukemia can be considered as malignant hematopoiesis, the existence of a developmental hierarchy in leukemia with a\\u000a malignant stem cell at its apex was postulated

Markus Müschen

367

Targeting Leukemic Stem Cells  

Microsoft Academic Search

The stem cell concept and asymmetric cell division are best understood in the hematopoietic system. Hematopoietic malignancies\\u000a resemble many of the known normal mature hematopoietic lineages that originate from stem cells. Leukemias in particular, were\\u000a shown to arise from leukemic stem cells. General characteristics of stem cells such as self-renewal, self-protection and proliferative\\u000a quiescence clearly point toward the need for

Angelika M. Burger

368

Largest Dinosaur Ever Discovered Found in Oklahoma  

NSDL National Science Digital Library

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

De Nie, Michael W.

369

Heme compounds in dinosaur trabecular bone  

PubMed Central

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.

Schweitzer, Mary H.; Marshall, Mark; Carron, Keith; Bohle, D. Scott; Busse, Scott C.; Arnold, Ernst V.; Barnard, Darlene; Horner, J. R.; Starkey, Jean R.

1997-01-01

370

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

Wandersee, James; Clary, Renee

2011-02-01

371

Common Avian Infection Plagued the Tyrant Dinosaurs  

PubMed Central

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

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

2009-01-01

372

The History of Dinosaur Footprint Discoveries in Wyoming with Emphasis on the Bighorn Basin  

Microsoft Academic Search

Dinosaur traces are well known from the western United States in the Colorado Plateau region (Utah, Colorado, New Mexico, and Arizona). Utah contains the greatest abundance of known and documented dinosaur footprints and trackways. Far less well known, however, is the occurrence and distribution of dinosaur footprint-bearing horizons in Wyoming. Scientific studies over the past 10 years have shown that

Erik P. Kvale; Debra L. Mickelson; Stephen T. Hasiotis; Gary D. Johnson

2004-01-01

373

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

374

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

375

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

376

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

Microsoft Academic Search

Dinosaur teeth from Paleocene channel fills have been interpreted as indicating dinosaur survival into the Paleocene. However, enormous potential for reworking exists because these records are restricted to large channel fills that are deeply incised into Cretaceous strata. Identification of reworked fossils is usually equivocal. This problem is illustrated by the Black Spring Coulee channel fill, a dinosaur-bearing Paleocene deposit

Donald L. Lofgren; Carol L. Hotton; Anthony C. Runkel

1990-01-01

377

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

Microsoft Academic Search

Dinosaur teeth from Paleocene channel fills have been interpreted as indicating dinosaur survival into the Paleocene. However, enormous potential for reworking exists because these records are restricted to large channel fills that are deeply incised into Cretaceous strata. Identification of reworked fossils is usually equivocal. This problem is illustrated by the Black Spring Coulee channel fill, a dinosaur-bearing Paleocene deposit

Donald L. Lofgren; Carol L. Hotton; Anthony C. Runkel

1990-01-01

378

First New Zealand record of probable dinosaur footprints from the Late Cretaceous North Cape Formation, northwest Nelson  

Microsoft Academic Search

Structures that are interpreted as dinosaur footprints are recorded from six localities within the Late Cretaceous (Maastrictian) aged North Cape Formation of northwest Nelson. These are the first dinosaur footprints to be recognised from New Zealand and the first occurrence of dinosaurs from the South Island, and add considerably to our knowledge of New Zealand dinosaurs, which currently is based

Greg H. Browne

2009-01-01

379

Mountain Building Triggered Late Cretaceous North American Megaherbivore Dinosaur Radiation  

PubMed Central

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

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

2012-01-01

380

Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds.  

PubMed

Spectacular fossils from the Early Cretaceous Jehol Group of northeastern China have greatly expanded our knowledge of the diversity and palaeobiology of dinosaurs and early birds, and contributed to our understanding of the origin of birds, of flight, and of feathers. Pennaceous (vaned) feathers and integumentary filaments are preserved in birds and non-avian theropod dinosaurs, but little is known of their microstructure. Here we report that melanosomes (colour-bearing organelles) are not only preserved in the pennaceous feathers of early birds, but also in an identical manner in integumentary filaments of non-avian dinosaurs, thus refuting recent claims that the filaments are partially decayed dermal collagen fibres. Examples of both eumelanosomes and phaeomelanosomes have been identified, and they are often preserved in life position within the structure of partially degraded feathers and filaments. Furthermore, the data here provide empirical evidence for reconstructing the colours and colour patterning of these extinct birds and theropod dinosaurs: for example, the dark-coloured stripes on the tail of the theropod dinosaur Sinosauropteryx can reasonably be inferred to have exhibited chestnut to reddish-brown tones. PMID:20107440

Zhang, Fucheng; Kearns, Stuart L; Orr, Patrick J; Benton, Michael J; Zhou, Zhonghe; Johnson, Diane; Xu, Xing; Wang, Xiaolin

2010-01-27

381

Stem cells: Skin regeneration and repair  

Microsoft Academic Search

Different types of stem cell maintain the skin's epidermis and contribute to its healing after damage. The identity of a stem-cell type that gives rise to different epidermal-cell lineages has just been revealed.

Cédric Blanpain

2010-01-01

382

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

383

Brain Tumor Stem Cells  

Microsoft Academic Search

Cancers are composed of heterogeneous cell popula- tions ranging from highly proliferative immature cells to more dif- ferentiated cells of various cell lineages. Recent advances in stem cell research have allowed for the demonstration of the existence of cancer stem cells in acute myeloid leukemia, breast cancer, and, most recently, in brain tumors. Each of these has some similarities with

ICHIRO NAKANO; HARLEY I. KORNBLUM

2006-01-01

384

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.

385

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

386

Sauropod dinosaurs evolved moderately sized genomes unrelated to body size  

PubMed Central

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

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

2009-01-01

387

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

388

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.

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

2005-01-01

389

Exceptional dinosaur fossils show ontogenetic development of early feathers  

Microsoft Academic Search

Recent discoveries of feathered dinosaur specimens have greatly improved our understanding of the origin and early evolution of feathers, but little information is available on the ontogenetic development of early feathers. Here we describe an early-juvenile specimen and a late-juvenile specimen, both referable to the oviraptorosaur Similicaudipteryx, recovered from the Lower Cretaceous Yixian Formation of western Liaoning, China. The two

Xing Xu; Xiaoting Zheng; Hailu You

2010-01-01

390

The Folklore of Dinosaur Trackways in China: Impact on Paleontology  

Microsoft Academic Search

Fossilized footprints made by extinct creatures have captured the attention of humans worldwide. Many different prescientific cultures have attempted to identify the trackmakers and account for the tracks of unfamiliar species. In China, local folklore about dinosaur footprints is preserved in oral traditions of great antiquity, which persist today in at least five regions with conspicuous tracksites. Although folk explanations

Lida Xing; Adrienne Mayor; Yu Chen; Jerald D. Harris; Michael E. Burns

2011-01-01

391

Dinosaur eggs and nesting behaviors: A paleobiological investigation  

Microsoft Academic Search

Although dinosaur eggs were first discovered and identified in the late 1800s, limited attention was given to the scientific value of oological fossils in contrast to observations based on skeletal features. Here, we offer a review of Mesozoic saurischian egg materials, in comparison with extant crocodilians and avians, and their paleobiological interpretation based either on the presence of embryos in

Gerald Grellet-Tinner; Luis Chiappe; Mark Norell; David Bottjer

2006-01-01

392

A dinosaur ichnocoenosis from the middle jurassic of Yorkshire, UK  

Microsoft Academic Search

An assemblage of dinosaur tracks from the undersurface of a sandstone bed in the Saltwick Formation (Middle Jurassic) of Yorkshire shows a range of morphological types, preservational variants and behavioral styles. The tracks are combinations of transmitted prints and underprints and include three distinct trackways. One trackway was made by an animal walking on exposed damp sand, another was left

M. A. Whyte; M. Romano

2001-01-01

393

The dinosaurs of Maghreb: the history of their discovery  

Microsoft Academic Search

A century of prospecting and exploring in North Africa has led to the discovery of remarkable dinosaur localities and excavating spectacular and diverse faunas from the Mesozoic outcrops. The first observations and publications were the work of courageous travellers, intrepid naturalists or motivated soldiers. They were followed by scientific expeditions with the main purpose of collecting more complete remains of

Philippe Taquet

2010-01-01

394

The evolution of vertebral pneumaticity in sauropod dinosaurs  

Microsoft Academic Search

The vertebrae of sauropod dinosaurs are characterized by complex architecture involving laminae, fossae, and internal chambers of various shapes and sizes. These structures are interpreted as osteological correlates of an intricate system of air sacs and pneumatic diverticula similar to that of birds. In basal sauropods pneumatic features are limited to fossae. Camerae and camellae are internalized pneumatic chambers independently

Mathew J. Wedel

2003-01-01

395

Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs  

Microsoft Academic Search

The vertebrae of sauropod dinosaurs are characterized by complex architecture involv- ing laminae, fossae, and internal chambers of various shapes and sizes. These structures are inter- preted as osteological correlates of a system of air sacs and pneumatic diverticula similar to that of birds. In extant birds, diverticula of the cervical air sacs pneumatize the cervical and anterior thoracic vertebrae.

Mathew J. Wedel

2003-01-01

396

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

397

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

398

Science Sampler: Metric-asaurus--Conceptualizing scale using dinosaur models  

NSDL National Science Digital Library

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 scal

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

2010-11-01

399

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

400

CRETACEOUS CLIMATE SENSITIVITY STUDY USING DINOSAUR & PLANT PALEOBIOGEOGRAPHY  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

401

Tracing the tumor lineage.  

PubMed

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

2010-05-05

402

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

PubMed

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

Chinsamy, Anusuya; Tumarkin-Deratzian, Allison

2009-09-01

403

Stem Cells in Immortal Hydra  

Microsoft Academic Search

\\u000a Hydra’s potential immortality and extensive capacity to regenerate and self-renew is due to the presence of three distinct stem\\u000a cell lineages: ectodermal and endodermal epithelial stem cells, and interstitial stem cells. Over the last few years, stem\\u000a cells in Hydra became well-defined in cellular terms of their biology. More recently, efforts using the nearly unlimited potential for tissue\\u000a manipulation combined

Thomas C. G. Bosch

404

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

PubMed

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

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

1986-05-01

405

Gradual Dinosaur Extinction and Simultaneous Ungulate Radiation in the Hell Creek Formation  

NASA Astrophysics Data System (ADS)

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

Sloan, Robert E.; Rigby, J. Keith; van Valen, Leigh M.; Gabriel, Diane

1986-05-01

406

Crosstalk between NOTCH and AKT signaling during murine megakaryocyte lineage specification  

PubMed Central

The NOTCH signaling pathway is implicated in a broad range of developmental processes, including cell fate decisions. However, the molecular basis for its role at the different steps of stem cell lineage commitment is unclear. We recently identified the NOTCH signaling pathway as a positive regulator of megakaryocyte lineage specification during hematopoiesis, but the developmental pathways that allow hematopoietic stem cell differentiation into the erythro-megakaryocytic lineages remain controversial. Here, we investigated the role of downstream mediators of NOTCH during megakaryopoiesis and report crosstalk between the NOTCH and PI3K/AKT pathways. We demonstrate the inhibitory role of phosphatase with tensin homolog and Forkhead Box class O factors on megakaryopoiesis in vivo. Finally, our data annotate developmental mechanisms in the hematopoietic system that enable a decision to be made either at the hematopoietic stem cell or the committed progenitor level to commit to the megakaryocyte lineage, supporting the existence of 2 distinct developmental pathways.

Cornejo, Melanie G.; Mabialah, Vinciane; Sykes, Stephen M.; Khandan, Tulasi; Lo Celso, Cristina; Lopez, Cecile K.; Rivera-Munoz, Paola; Rameau, Philippe; Tothova, Zuzana; Aster, Jon C.; DePinho, Ronald A.; Scadden, David T.; Gilliland, D. Gary

2011-01-01

407

A bizarre predatory dinosaur from the Late Cretaceous of Madagascar.  

PubMed

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

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

2001-01-25

408

An Abelisauroid Theropod Dinosaur from the Turonian of Madagascar  

PubMed Central

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

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

2013-01-01

409

An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures.  

PubMed

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

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

2009-03-19

410

Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus  

PubMed Central

Background Extended 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. Marginocephalians (pachycephalosaurids + ceratopsids) undergo comparable and extreme cranial morphological change during ontogeny. Methodology/Principal Findings Cranial histology, morphology and computer tomography reveal patterns of internal skull development that show the purported diagnostic characters for the pachycephalosaurids Dracorex hogwartsia and Stygimoloch spinifer are ontogenetically derived features. Coronal histological sections of the frontoparietal dome of an adult Pachycephalosaurus wyomingensis reveal a dense structure composed of metaplastic bone with a variety of extremely fibrous and acellular tissue. Coronal histological sections and computer tomography of a skull and frontoparietal dome of Stygimoloch spinifer reveal an open intrafrontal suture indicative of a subadult stage of development. These dinosaurs employed metaplasia to rapidly grow and change the size and shape of their horns, cranial ornaments and frontoparietal domes, resulting in extreme cranial alterations during late stages of growth. We propose that Dracorex hogwartsia, Stygimoloch spinifer and Pachycephalosaurus wyomingensis are the same taxon and represent an ontogenetic series united by shared morphology and increasing skull length. Conclusions/Significance Dracorex hogwartsia (juvenile) and Stygimoloch spinifer (subadult) are reinterpreted as younger growth stages of Pachycephalosaurus wyomingensis (adult). This synonymy reduces the number of pachycephalosaurid taxa from the Upper Cretaceous of North America and demonstrates the importance of cranial ontogeny in evaluating dinosaur diversity and taxonomy. These growth stages reflect a continuum rather than specific developmental steps defined by “known” terminal morphologies.

Horner, John R.; Goodwin, Mark B.

2009-01-01

411

Proteins in the fossil bone of the dinosaur, seismosaurus  

Microsoft Academic Search

Proteins have been successfully extracted from the fossil vertebra of a 150-million-year-old sauropod dinosaur (“Seismosaurus”) recently excavated from the Morrison Formation of New Mexico. HCl and guanidine·HCl extracts of the fossil bone and its sandstone matrix were concentrated, demineralized, and resolved into a number of different protein fractions by reversed-phase high-performance liquid chromatography (HPLC). One of these fractions had the

L. R. Gurley; J. G. Valdez; W. D. Spall; B. F. Smith; D. D. Gillette

1991-01-01

412

Romanian late cretaceous dinosaurs: Big dwarfs or small giants?  

Microsoft Academic Search

It has been argued that the Late Cretaceous dinosaurs from Transylvania were affected by dwarfism as a consequence of their evolution in an insular habit. However, several bones from Nopcsa's collections housed in London and Budapest shows that some Transylvanian saltasaurids reached lengths of 10–15 m. These multi-ton animals can hardly be considered as dwarfs, even by dinosaurian standards. It is

Jean le Loeuff

2005-01-01

413

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

Microsoft Academic Search

This is somewhat extended version of the talk given at the Gran Sasso Summer\\u000aInstitute: Massive Neutrinos in Physics and Astrophysics. It describes general\\u000aideas about mirror world, extra spatial dimensions and dinosaur extinction.\\u000aSome suggestions are made how these seemingly different things can be related\\u000ato each other.

Z. K. Silagadze

2000-01-01

414

The postcranial skeleton of the ornithopod dinosaur Tenontosaurus tilletti  

Microsoft Academic Search

Tenontosaurus tilletti is a moderate-sized ornithopod dinosaur from the Lower Cretaceous (Aptian–Albian) Cloverly Formation in Montana and Wyoming. Tenontosaurus remains are abundant. The vertebral count is 12-16-5-60+, the extremely long tail comprising approximately twothirds the length of the animal. Ossified epaxial tendons are arranged in bundles to each side of the neural spines of the dorsal, sacral, and caudal vertebrae.

Catherine A. Forster

1990-01-01

415

Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon  

Microsoft Academic Search

Wedel, M.J., Cifelli, R.L., & Sanders, R.K. 2000. Osteology, paleobiology, and relation- ships of the sauropod dinosaur Sauroposeidon. -Acta Palaeontologica Polonica 45,4, 343-388. Sauroposeidon proteles is a large brachiosaurid sauropod recently described from the Antlers Formation (Aptian-Albian) of southeastern Oklahoma. Sauroposeidon repre- sents the culmination of brachiosaurid trends toward lengthening and lightening the neck, and its cervical vertebrae are characterized

MATHEW J. WEDEL; RICHARD L. CIFELLI; R. KENT SANDERS

416

Ornithomimidae (Bird Mimics): The Ostrich-Like Dinosaurs  

NSDL National Science Digital Library

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

417

Low beta diversity of Maastrichtian dinosaurs of North America  

PubMed Central

Beta diversity is an important component of large-scale patterns of biodiversity, but its explicit examination is more difficult than that of alpha diversity. Only recently have data sets large enough been presented to begin assessing global patterns of species turnover, especially in the fossil record. We present here an analysis of beta diversity of a Maastrichtian (71–65 million years old) assemblage of dinosaurs from the Western Interior of North America, a region that covers ?1.5 × 106 km2, borders an epicontinental sea, and spans ?20° of latitude. Previous qualitative analyses have suggested regional groupings of these dinosaurs and generally concluded that there were multiple distinct faunal regions. However, these studies did not directly account for sampling bias, which may artificially decrease similarity and increase turnover between regions. Our analysis used abundance-based data to account for sampling intensity and was unable to support any hypothesis of multiple distinct faunas; earlier hypothesized faunal delineations were likely a sampling artifact. Our results indicate a low beta diversity and support a single dinosaur community within the entire Western Interior region of latest Cretaceous North America. Homogeneous environments are a known driver of low modern beta diversities, and the warm equable climate of the late Cretaceous modulated by the epicontenental seaway is inferred to be an underlying influence on the low beta diversity of this ancient ecosystem.

Vavrek, Matthew J.; Larsson, Hans C. E.

2010-01-01

418

Gastric Epithelial Stem Cells  

PubMed Central

Advances in our understanding of stem cells in the gastrointestinal tract include the identification of molecular markers of stem and early progenitor cells in the small intestine. Although gastric epithelial stem cells have been localized, little is known about their molecular biology. Recent reports describe the use of inducible Cre recombinase activity to indelibly label candidate stem cells and their progeny in the distal stomach, (ie, the antrum and pylorus). No such lineage labeling of epithelial stem cells has been reported in the gastric body (corpus). Among stem cells in the alimentary canal, those of the adult corpus are unique in that they lie close to the lumen and increase proliferation following loss of a single mature progeny lineage, the acid-secreting parietal cell. They are also unique in that they neither depend on Wnt signaling nor express the surface marker Lgr5. Because pathogenesis of gastric adenocarcinoma has been associated with abnormal patterns of gastric differentiation and with chronic tissue injury, there has been much research on the response of stomach epithelial stem cells to inflammation. Chronic inflammation, as induced by infection with Helicobacter pylori, affects differentiation and promotes metaplasias. Several studies have identified cellular and molecular mechanisms in spasmolytic polypeptide–expressing (pseudopyloric) metaplasia. Researchers have also begun to identify signaling pathways and events that take place during embryonic development that eventually establish the adult stem cells to maintain the specific features and functions of the stomach mucosa. We review the cytologic, molecular, functional, and developmental properties of gastric epithelial stem cells.

MILLS, JASON C.; SHIVDASANI, RAMESH A.

2013-01-01

419

Feathered dinosaurs from China and the evolution of major avian characters  

Microsoft Academic Search

Recent discoveries of feathered dinosaurs from Early Cretaceous deposits in Liaoning, China, have not only lent strongest support for the dinosaurian hypothesis of bird origins, but have also provided much-needed information about the origins of feathers and avian flight. Preliminary analysis of character evolution suggests that the major avian osteological characters were acquired during the early evolution of maniraptoran dinosaurs.

Xing XU

2006-01-01

420

The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs  

Microsoft Academic Search

A new discovery of skeletons of Revueltosaurus callenderi from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona clearly shows that Revueltosaurus is not an ornithischian dinosaur as previously supposed. Features such as the presence of a postfrontal, crocodile-normal ankle and paramedian osteoderms with anterior bars place R. callenderi within the Pseudosuchia, closer to crocodylomorphs than to dinosaurs.

William G. Parker; Randall B. Irmis; Sterling J. Nesbitt; Jeffrey W. Martz; Lori S. Browne

2005-01-01

421

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

NSDL National Science Digital Library

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

422

Dinosaurs in the Dark: Grades 2-3: 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 grade two through grade three reading level. This is a PDF containing the informational text and a glossary.

Fries-Gaither, Jessica

423

NO DEFINITIVE EVIDENCE OF PALEOCENE DINOSAURS IN THE SAN JUAN BASIN  

Microsoft Academic Search

In a recent article in this journal, Fassett (2009) concludes that dinosaur fossils of Paleocene age are present in the San Juan Basin of New Mexico-Colorado. However, we argue that, based on existing data, Fassett has failed to produce compelling evi- dence to support this conclusion. In the San Juan Basin, only one arguably reworked dinosaur bone (an isolated hadrosaur

Spencer G. Lucas; Robert M. Sullivan; Steven M. Cather; Steven E. Jasinski; Denver W. Fowler; Andrew B. Heckert; Justin A. Spielmann; Adrian P. Hunt

2009-01-01

424

Gradual Dinosaur Extinction and Simultaneous Ungulate Radiation in the Hell Creek Formation  

Microsoft Academic Search

Dinosaur extinction in Montana, Alberta, and Wyoming was a gradual process that began 7 million years before the end of the Cretaceous and accelerated rapidly in the final 0.3 million years of the Cretaceous, during the interval of apparent competition from rapidly evolving immigrating ungulates. This interval involves rapid reduction in both diversity and population density of dinosaurs. The last

Robert E. Sloan; J. Keith Rigby; Leigh M. van Valen; Diane Gabriel

1986-01-01

425

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

426

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

427

The Pathogenesis of Mixed Lineage Leukemia  

PubMed Central

Aggressive leukemias arise in both children and adults as a result of rearrangements to the Mixed Lineage Leukemia (MLL) gene located on chromosome 11q23. The MLL gene encodes a large histone methyltransferase that directly binds and positively regulates gene transcription including HOX genes. MLL is involved in chromosomal translocations, partial tandem duplication and amplifications, all of which result in hematopoietic malignancies due to sustained HOX expression and stalled differentiation. MLL lesions are associated with both acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL) and are usually associated with a relatively poor prognosis despite improved treatment options like allogeneic hematopoietic stem cell transplantation underscoring the need for new treatment regimens. Recent advances have begun to reveal the molecular mechanisms driving MLL associated leukemias which have provided opportunities for therapeutic development. Here we discuss the etiology of MLL leukemias and potential directions for therapeutic development.

Muntean, Andrew G.; Hess, Jay L.

2012-01-01

428

Lineage determinants in early endocrine development.  

PubMed

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

2012-06-21

429

Random roots and lineage sorting.  

PubMed

Lineage sorting has been suggested as a major force in generating incongruent phylogenetic signal when multiple gene partitions are examined. The degree of lineage sorting can be estimated using the coalescent process and simulation studies have also pointed to a major role for incomplete lineage sorting as a factor in phylogenetic inference. Some recent empirical studies point to an extreme role for this phenomenon with up to 50-60% of all informative genes showing incongruence as a result of lineage sorting. Here, we examine seven large multi-partition genome level data sets over a large range of taxonomic representation. We took the approach of examining outgroup choice and its impact on tree topology, by swapping outgroups into analyses with successively larger genetics distances to the ingroup. Our results indicate a linear relationship of outgroup distance with incongruence in the data sets we examined suggesting a strong random rooting effect. In addition, we attempted to estimate the degree of lineage sorting in several large genome level data sets by examining triads of very closely related taxa. This exercise resulted in much lower estimates of incongruent genes that could be the result of lineage sorting, with an overall estimate of around 10% of the total number of genes in a genome showing incongruence as a result of true lineage sorting. Finally we examined the behavior of likelihood and parsimony approaches on the random rooting phenomenon. Likelihood tends to stabilize incongruence as outgroups get further and further away from the ingroup. In one extreme case, likelihood overcompensates for sequence divergence but increases random rooting causing long branch repulsion. PMID:22445448

Rosenfeld, Jeffrey A; Payne, Ansel; DeSalle, Rob

2012-03-14

430

Use of ground penetrating radar in detecting fossilized dinosaur bones  

NASA Astrophysics Data System (ADS)

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

Meglich, Todd M.

2000-04-01

431

The history of dinosaur footprint discoveries in Wyoming with emphasis on the Bighorn basin  

USGS Publications Warehouse

Dinosaur traces are well known from the western United States in the Colorado Plateau region (Utah, Colorado, New Mexico, and Arizona). Utah contains the greatest abundance of known and documented dinosaur footprints and trackways. Far less well known, however, is the occurrence and distribution of dinosaur footprint-bearing horizons in Wyoming. Scientific studies over the past 10 years have shown that three of the four Middle and Upper Jurassic formations in northern Wyoming contain dinosaur footprints. Two of the footprint-bearing horizons are located in geologic intervals that were once thought to have been deposited in offshore to nearshore marine settings and represent rare North American examples of Middle Jurassic (Bajocian and Bathonian) dinosaur remains. Some of these new Wyoming sites can be correlated to known dinosaur footprint-bearing horizons or intervals in Utah. Wyoming has a great potential for additional discoveries of new dinosaur footprint-bearing horizons, and further prospecting and study is warranted and will ultimately lead to a much better understanding of the geographic distribution and behavior of the potential footprint-makers. ?? Taylor and Francis Inc.

Kvale, E. P.; Mickelson, D. L.; Hasiotis, S. T.; Johnson, G. D.

2003-01-01

432

Dinosaur eggshell geochemistry as an indicator of Central Asian Cretaceous paleoenvironments  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

433

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

NASA Astrophysics Data System (ADS)

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

Lofgren, Donald L.; Hotton, Carol L.; Runkel, Anthony C.

1990-09-01

434

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

SciTech Connect

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

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

1990-09-01

435

Comparison of Multi-Lineage Cells from Human Adipose Tissue and Bone Marrow  

Microsoft Academic Search

Our laboratory has recently characterized a population of cells from adipose tissue, termed processed lipoaspirate (PLA) cells, which have multi-lineage potential similar to bone-marrow-derived mesenchymal stem cells (MSCs). This study is the first comparison of PLA cells and MSCs isolated from the same patient. No significant differences were observed for yield of adherent stromal cells, growth kinetics, cell senescence, multi-lineage

Daniel A. De Ugarte; Kouki Morizono; Amir Elbarbary; Zeni Alfonso; Patricia A. Zuk; Min Zhu; Jason L. Dragoo; Peter Ashjian; Bert Thomas; Prosper Benhaim; Irvin Chen; John Fraser; Marc H. Hedrick

2003-01-01

436

Notch1 and Notch2 exhibit unique patterns of expression in human B-lineage cells  

Microsoft Academic Search

The Notch genes encode a conserved family of receptors that influence developmental fate in many species. Prior studies have indicated that Notch-1 and Notch-2 signaling influence the development of hematopoietic stems cells and thymocytes, but little is known regarding Notch expression and function in B-lineage cells. We analyzed the expression of Notch recepto