bluuebunny/crossref_metadata_2025_split huggingface dataset:
Up‐regulation of a novel integrin α‐chain (αmt) on human fetal myotubes
Authors: Gullberg Donald , Velling Teet , Sjöberg Gunnar , Sejersen Thomas 
Published: February 2005

AbstractIntegrin expression and distribution was studied in cloned human fetal G6 myoblasts and myotubes. Immunoprecipitation of β1 integrins from surface iodinated and metabolically labeled G6 cells typically showed a five‐fold induction of a β1 integrin associated protein upon differentiation. Under non‐reducing conditions this β1 associated protein migrated as 145 kD. No such β1 associated protein was observed in the myogenic L8 rat cell line, before or after differentiation. The β1 integrin associated cell surface protein present in G6 myotubes remained associated with the β1 subunit in the presence of 1% Triton X‐100 and 0.5 M NaCl. Like integrin α‐chains, the protein dissociated from the β1 integrin subunit at low pH. Immunoprecipitation of G6 myotubes further indicated the presence of α, α, α5, and αa integrins, and small amounts of α4 and α6 integrins. Immunodepletion with integrin α‐chain antibodies to α1, α3, α4, α5, α6, and αv integrin chains could not deplete the β1 integrin associated protein, indicating that it did not interact with any of these known integrin heterodimers. Upon treatment with reducing agents, the β1 integrin associated protein migrated in SDS‐PAGE as a 155 kD protein. The decreased mobility in SDS‐PAGE upon reduction is a feature shared with α1, α2, and α9 integrin α‐chains. Antibodies to α1 immunoprecipitated an integrin heterodimer distinct from the 155 kD protein. Antibodies to α2 and α9 failed to immunoprecipitate proteins from G6 myotubes and Northern blot analysis likewise failed to detect messages for these two integrin α‐chains. Immunohistochemistry with antibodies to different integrins of fetal thigh muscles showed staining of α6 integrin at the sarcolemma. Antibodies to α2 and α9 stained keratinocytes and other non‐muscle cells in the fetal leg, but no signal was detected for α2 and α9 integrin on fetal myotubes. Based on these characteristics, we propose that the induced protein is a hitherto unidentified integrin α‐chain on myotubes that we name αmt. Our finding of a novel integrin α‐chain that is induced upon myogenic differentiation supports the idea that different integrins are important for myogenesis during different developmental stages, and we suggest that αmt takes part in early human myotube formation. © 1995 wiley‐Liss, Inc.
CCAAT/Enhancer binding protein isoforms expression in the colon of neonatal mice
Authors: Blais Sylvie , Boudreau François , Beaulieu Jean‐françois , Asselin Claude 
Published: February 2005

AbstractDevelopment of murine proximal colon follows a complex pattern of morphological and functional differentiation. Molecular mechanisms and factors responsible for colonspecific gene expression remain to be established. In an attempt to identify some of these factors, we examined the expression of the α, β, and δ isoforms of the CCAAT/enhancer binding protein (C/EBP) transcription factor gene family during murine colon development. Whereas C/EBPα mRNA levels are reduced during the third post‐natal week, C/EBPα 42 and 30 kD proteins levels decrease between post‐natal days 8 and 21. C/EBPβ mRNA levels increase between post‐natal days 4 and 8 and remain constant subsequently, in contrast to a decrease in C/EBPβ protein levels between post‐natal days 11 and 15. C/EBPδ mRNA levels increase gradually while C/EBPδ protein levels show variations during post‐natal development. Changes in C/EBP DNA binding activity coincides with modifications in C/EBP isoforms expression. By indirect immunofluorescence, we show restriction of C/EBPα expression to differentiated surface epithelial cells during crypt formation. C/EBPβ is predominantly nuclear with some cytoplasmic staining at all developmental stages. C/EBPβ and δ are both predominantly nuclear in crypt and differentiated surface epithelial cells, as well as in various cells of the lamina propria and muscular layers. Thus, specific C/EBP isoforms are differentially regulated during murine colon post‐natal development. Differential C/EBP isoforms pattern of expression suggests a role for these transcription factors in colon‐specific gene expression during development. © 1995 wiley‐Liss, Inc.
Role for platelet‐derived growth factor‐like and epidermal growth factor‐like signaling pathways in gastrulation and spiculogenesis in the Lytechinus sea urchin embryo
Authors: Ramachandran Ravi K. , Govindarajan Venkatesh , Seid Christopher A. , Patil Sonali , Tomlinson Craig R. 
Published: February 2005

AbstractThe mechanisms underlying sea urchin gastrulation and spiculogenesis have been sought for decades. We have identified two growth factor signaling pathways that are involved in these developmental events. Antibodies against mammalian platelet‐derived growth factor (PDGF) receptor‐β inhibited gastrulation and spiculogenesis, and antibodies against human epidermal growth factor (EGF) receptor disrupted gastrulation and spicule placement in Lytechinus pictus and L. variegatus embryos. Our studies suggested that the antibodies affect development by inhibiting rather than activating the signaling pathways. Polyclonal and monoclonal antibodies against the mammalian receptors recognized specifically Lytechinus proteins of the expected size of 170–180 × 103 Mr. Growth factor binding assays indicated that there are approximately 1.25 × 104 platelet‐derived growth factor‐like receptors per cell at the mesenchyme blastula stage of L. pictus, and human platelet‐derived growth factor bound with an apparent affinity of KD = 4.4 nM to dissociated cells at the mesenchyme blastula stage. Immunolabelling experiments showed that at the gastrula stage, the Lytechinus platelet‐derived growth factor‐like receptors are located on the primary mesenchyme cells, the gut, and most prominently on the secondary mesenchyme cells and the stomodeum. The epidermal growth factor‐like receptors stained less intensely on the gut and primary and secondary mesenchyme cells. Both receptors are expressed on the ciliary band and the gut of the pluteus larva but only the PDGF‐like receptors is expressed on the primary mesenchyme cells. Pulse studies showed that the embryos are sensitive to the platelet‐derived growth factor receptor‐β and epidermal growth factor receptor antibodies from the blastula to sometime between the mesenchyme blastula and midgastrula stages. We show that antibodies enter the blastocoel as late as the gastrula stage. Our results suggest that platelet‐derived growth factor‐like and epidermal growth factor‐like signaling pathways are involved in the early differentiation and morphogenesis of the sea urchin gut and spicules. © 1995 wiley‐Liss, Inc.
Developmental expression of H‐2K major histocompatibility complex class I transgenes requires the presence of proximal introns
Authors: Drezen J. M. , Cohen‐Tannoudji M. , Pournin S. , Babinet C. , Morello D. 
Published: February 2005

AbstractThe pattern of expression of the H‐2K major histocompatibility complex (MHC) class I gene is complex. During embryonic development H‐2K mRNA, detectable from midgestation, is poorly expressed. In the adult, H‐2K expression is nearly ubiquitous but transcriptional regulation occurs leading to different mRNA levels in the different organs of the mouse. In vitro studies have shown that most of the regulatory elements controlling H‐2K gene transcription are located in the 5′ region of the gene. However, using fusion transgenes in which reporter genes were under the control of 2 kb of H‐2K 5′ regulatory region, we have previously shown that this region, was not sufficient to ensure correct developmental transgene expression. By contrast, a native 9.25 kb H‐2K transgene was expressed appropriately both in the adult and in the embryo. In order to localise more precisely the cis‐acting regulatory sequences involved in H‐2K developmental expression, we have now constructed new transgenic lines containing H‐2Kb transgenes that were deleted from specific parts of the H‐2Kb gene. We show that deletion of either the H‐2K 3′ flanking region or the 5 (out of 7) distal introns results in an expression of the transgenes which is similar to that of the endogenous H‐2K gene, both in the adult and during embryonic development. By contrast, deletion of all the introns or of the two proximal ones abrogates H‐2K transgene expression. Our data reveal the complexity of H‐2K regulation and highlight the crucial role of proximal introns in H‐2K expression in the living organism. © 1995 wiley‐Liss, Inc.
Ubiquitin‐protein conjugates selectively distribute during early chicken embryogenesis
Authors: Wunsch Ann M. , Haas Arthur L. 
Published: February 2005

AbstractThe major mechanism for proteloysis in eucaryotes involves an ATP‐dependent pathway for which the covalent attachment of ubiquitin targets proteins for degradation. The involvement of ubiquitin conjugation in early embryonic vertebrate development was investigated by examinining the amounts and localization of ubiquitin conjugates at different stages of development in the chicken using an affinity‐purified antibody specific for conjugated ubiquitin. Solid phase immunochemical assays measuring whole embryo pools of free and conjugated ubiquitin demonstrated a progressive increase increase in conjugate pools to stage 18, followed by a decline to stage 24. In contrast, levels of free polypeptide showed a dramatic increase after stage 5, indicating a change in the dynamics of the two pools during develoment. Immunohistochemistry revealed that the distribution of ubiquitin adducts between stages 3 and 22 was pronounced in regions undergoing extensive cellular remodeling. Ubiquitin conjugates were detected in the primitive streak where cells ingress during gastrulastion. The presence of these degradative intermediate in both neuroectodermal cells of the neural folds and subsquent neural crest cells migrating from the dorsum of the neural tube is consistent with an involvement in key morphogenetic events. The localization of ubiquitin conjugates at other selected tissue interfaces including limb bud ectoderm/mesoderm, and cardiac atrioventricular myocardium/endothelium suggests an active role for ubiquitin‐mediated protein modification in similar developmental interactions. Conjugates were distributed first between somites, then in myotomes with a pattern spatially identical to that of the ubiquitin conjugating enzyme, E214K, the major cognate isozyme for isopeptide ligase (E3)‐dependent degradation. The potential involvement of ubiquitin conjugation at sites of epithelialmesenchymal associations was further analyzed ion culture using atrioventricular canal (AV) endothelium. Immunoreactivity was abundant in cells immediately prior to and during their transformation into mesenchyme. Collectively, the specific temporal and, spatial changes in ubiquitin conjugates during early vertebrate development suggest a regulatory role for this degradative pathway in the cellular remodeling accompanying embryonic growth and differentiation. © 1995 wiley‐Liss, Inc.
Developmental expression of two members of a new class of transcription factors: I. Expression of aryl hydrocarbon receptor in the C57BL/6N mouse embryo
Authors: Abbott B. D. , Birnbaum L. S. , Perdew G. H. 
Published: February 2005

AbstractThe aryl hydrocarbon receptor (AhR) is a ligand‐activated transcription factor with a basic region/helix‐loop‐helix (bHLH) motif. AhR has been sequenced and the functional domains defined and there is information on the formation of complexes with other peptides and interactions with DNA, although these areas continue to be investigated. AhR mediates many biological effects such as developmental toxicity, including induction of cleft palate and hydronephrosis. This regulatory protein is expressed in embryonic liver and has been immunohistochemically localized in cells of human and mouse secondary palate. The expression of AhR in embryonic tissues and its ability to disrupt development suggests a significant role for this protein in development. The present study examines the pattern of AhR expression in the C57BL/6N mouse embryo from gestation days (GD) 10–16, using in situ hybridization and immunohistochemical analysis. AhR mRNA was localized with 35S‐RNA antisense riboprobe (cAh1 probe, 1.8 Kb amino terminal DNA). AhR protein was localized with purified monoclonal antibody (RPT‐9) raised against the N‐terminal peptide sequence. AhR mRNA and protein were expressed in GD 10–13 neuroepithelium, and as development progressed the levels in brain decreased. GD 10–12 embryos also showed AhR in branchial arches, heart, somites, and liver. AhR protein and mRNA in heart were highest at GD 10–11 and decreased with age. In liver, AhR mRNA and protein levels increased and nuclear localization became more pronounced with gestational age. In GD 14–16 embryos levels in liver and adrenal were highest, but AhR was present in ectoderm, bone, and muscle. AhR expression was specific for both cell type, organ/tissue, and developmental stage, suggesting that this novel ligand‐activated transcriptional regulator may be important in normal embryonic development. © 1995 wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
Developmental expression of two members of a new class of transcription factors: II. Expression of aryl hydrocarbon receptor nuclear translocator in the C57BL/6N mouse embryo
Authors: Abbott B. D. , Probst M. R. 
Published: February 2005

AbstractThe aryl hydrocarbon receptor (AhR) and the AhR nuclear translocator protein (ARNT) are basic‐helix‐loop‐helix (bHLH) proteins involved in transcriptional regulation. The AhR is a ligand‐activated partner of the ARNT protein. Both proteins are required to transcriptionally regulate gene expression. ARNT must be complexed to AhR to permit binding to the regulatory DNA sequence. The AhR‐ligand complex is known to mediate a range of biological responses, such as developmental toxicity, induction of cleft palate, and hydronephrosis. AhR and ARNT are expressed in human embryonic palatal cells and AhR was recently shown to have a specific developmental pattern of expression in the mouse embryo. In the present study, expression of ARNT is characterized in C57BL/6N mouse embryos from gestation day (GD) 10–16 using immunohistochemistry and in situ hybridization. An affinity purified antibody against human ARNT (1.1 μg/ml) was detected with an avidinbiotin‐peroxidase complex. ARNT mRNA was localized with a 35S‐RNA probe from pBM5/NEOM1–1. Specific spatial and temporal patterns of ANRT expression emerged and mRNA and protein expression correlated. The GD 10–11 embryos showed highest levels of ARNT in neuroepithelial cells of the neural tube, visceral arches, otic and optic placodes, and preganglionic complexes. The heart also had significant expression of ARNT with strong nuclear localization. After GD11, expression in heart and brain declined. In GD 12–13 embryos expression was highest in the liver where expression increased from GD 12–16. At GD 15–16 the highest levels of ARNT occurred in adrenal gland and liver, although ARNT was also detected in submandibular gland, ectoderm, tongue, bone, and muscle. In all of these tissues ARNT was cytoplasmic as well as nuclear, except in some of the cortical adrenal cells in which ARNT was strongly cytoplasmic with little or no nuclear localization. These specific patterns of ARNT expression, which differ in certain tissues from the expression of AhR, suggest that ARNT may have additional roles in normal embryonic development. © 1995 wiley‐Liss, Inc.
Limb deformity proteins during avian neurulation and sense organ development
Authors: De La Pompa José Luis , James Dominic , Zeller Rolf 
Published: February 2005

AbstractThe nuclear Limb deformity (Ld) proteins (formins) are expressed during the avian primitive streak stages. Initially, they are detected predominantly in cells of the forming notochord, scattered mesodermal precursors and the induced neural plate. No expression is detected in endodermal cells. The subsequent graded distribution of Ld positive cells along the anterior‐posterior axis of the neural tube follows the antero‐posterior progression of its differentiation. The Ld proteins are also differentially expressed during induction and development of both the inner ear and eye. An unequal distribution of Ld proteins along the dorso‐ventral axis of the otic vesicle is observed during its initial patterning. In the eye, the Ld proteins are expressed by the optic vesicle during secondary induction of the lens placode. Following induction, the proteins are also expressed by the newly formed lens placode, a process which is reminiscent of homeogenetic induction. During differentiation of the retina and lens, the Ld domains seem to demarcate territories, giving rise to specific eye structures. A comparative analysis of the Ld distribution and BrdU incorporation in the two sense organs indicates that the proteins are predominantly expressed by committed and/or differentiating (post‐mitotic) cells. In general, expression of Ld proteins is induced during determination and remains during differentiation of particular cell‐types. This study implies that the nuclear Ld rproteins are involved in morphogenesis of both neuro‐ectodermal and mesodermal structures. © 1995 wiley‐Liss, Inc.
During secondary myotube formation, primary myotubes preferentially absorb new nuclei at their ends
Authors: Zhang Ming , McLennan Ian S. 
Published: February 2005

AbstractDeveloping muscles contain at least two types of myoblasts. Early myoblasts are the first myoblast to form and are the only myoblasts present during primary myotube formation. By the time secondary myotube formation begins, early myoblasts are rare and late myoblasts are common. The late myoblasts have been postulated to give rise to secondary myotubes. While this is generally accepted, it is unclear whether late myoblasts also contribute to the growth of primary myotubes. One study has produced evidence that myoblasts present during secondary myogenesis selectively fuse with each other or with secondary myotubes, but not with primary myotubes (Harris et al. [1989a] Development 107:771–784). However, the sizes of primary myotubes increase during secondary myotube formation. We have therefore re‐examined the question of whether primary myotubes absorb new nuclei during secondary myotube formation. Pregnant rats were given a single intraperitoneal injection of 5 mg of 5‐bromodeoxyuridine (BrdU) on one embryonic day (from E13 to E19) and their embryos removed on E20. The brominated‐nuclei were labelled with an antibody to BrdU and the myotubes were marked with anti‐myosin antibodies. Double labelled sections from the soleus, tibialis anterior, and extensor digitorum longus muscles were examined with a confocal microscope. The numbers and locations of labelled nuclear profiles in primary and secondary myotubes were counted and recorded. The results show: (1) that primary myotubes absorb nuclei at all stages of development, including the period of secondary myotube formation; (2) that in the early stages of secondary myotube formation, more myoblasts fuse with primary than secondary myotubes whereas this situation is reversed by the end of secondary myotube formation; and (3) that the nuclei added to primary and secondary myotubes during the early stages of their formation are located within the middle of E20 muscles. The nuclei added to growing myotubes are preferentially located at the ends of the muscles. © 1995 wiley‐Liss, Inc.
Ectodermal stimulation of the production of hyaluronan‐dependent pericellular matrix by embryonic limb mesodermal cells
Authors: Knudson Cheryl B. , Munaim Syeda I. , Toole Bryan P. 
Published: February 2005

AbstractInteraction of ectoderm and underlying mesoderm is essential for normal vertebrate limb morphogenesis. One of the functions of limb bud ectoderm is its influence on the composition of extracellular matrix in subectodermal mesoderm, which in turn participates in morphogenesis of this region of the limb. This matrix is highly enriched in hyaluronan, even at the time when the level of hyaluronan in the chondrogenic and myogenic regions of the limb decreases, due to secretion of a stimulatory factor by the ectoderm. In this study we show that limb bud ectoderm not only stimulates hyaluronan synthesis but induces formation of large hyaluronan‐dependent, pericellular matrices around cultured limb bud mesodermal cells. The ectodermal activity is mimicked in great part by fibroblast growth factor‐2 and transforming growth factor‐β, and antibodies to these proteins inhibit induction of mesodermal pericellular matrix by the ectodermal factor. It has been shown by other investigators that fibroblast growth factor‐2 is produced by limb ectoderm whereas transforming growth factor‐β is present in limb mesodermal tissues. Thus we conclude that the unique properties of mesodermally produced matrix underlying limb bud ectoderm are regulated, at least in part, by ectodermal fibroblast growth factor‐2, probably in concert with mesodermal transforming growth factor‐β. © 1995 wiley‐Liss, Inc.
Developmental expression of a type II collagen/β‐galactosidase fusion gene in transgenic mice
Authors: Metsäranta Marjo , Garofalo Silvio , Smith Chad , Niederreither Karen , De Crombrugghe Benoit , Vuorio Eero 
Published: February 2005

AbstractThe correct temporal and spatial expression of the type II collagen gene is believed to be important for normal development and growth of the skeleton and the eye, i.e., tissues where the protein product is predominantly found. To study transcriptinal activation of type II collagen gene in skeletal and nonskeletal tissues we produced transgenic mice carrying murine proα1(II) collagen/β‐galactosidase fusion gene constructs. The expression of the fusion gene was found to depend on the presence of intron 1 sequences: constructs with most of intron 1 deleted failed to reveal any β‐galactosidase activity confirming the important role of regulatory sequences within intron 1 of the gene. High‐level expression of the functional construct was clearly confined to cartilaginous tissues but transient low‐level expression was also observed in extraskeletal locations, such as the developing brain and the notochord. The results demonstrate that the regulatory elements in the proα1(II) collagen/β‐galactosidase fusion gene construct confer both temporal and spatial specificity indistinguishable from that of the endogenous proα1(II) collagen gene as determined by the presence of the corresponding mRNA by in situ hybridization. Furthermore the β‐galactosidase activity correlated well with the progression of chondrogenesis as seen by staining of whole mouse embryos with Alizarin red S and Alcian blue in the hybrid mouse strain used for microinjections. The transgenic mouse line produced should prove useful for studies on various aspects of chondrogenesis. Furthermore, the data shows that the regulatory elements present in the construct are sufficient for targetting the expression of other genes in cartilage. © 1995 wiley‐Liss, Inc.