bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of actin and assembly of connectin (titin) during myofibrillogenesis in embryonic chick cardiac muscle cells in vitro
Authors: Komiyama Masatoshi , Kouchi Katsunori , Maruyama Koscak , Shimada Yutaka 
Published: February 2005

AbstractImmunogold electron microscopy of cardiac myocytes microinjected with biotin‐labeled actin showed that gold labeling was first found around the A band level of myofibrils at their proximal parts. This observation suggests that polymerization of actin and/or the addition of newly formed actin filaments occurs preferentially in association with myosin filaments to increase the myofibrillar girth. At the distal portions of developing myofibrils, their terminal ends were initially labeled, suggesting that continued reorganization and/or de novo formation of myofibrils occurs at these locations. Soon, gold particles were seen along the termini of growing myofibrils. This appears to indicate that actin subunits are added at the membrane‐associated ends of preexisting actin filaments to increase the length of myofibrils. Adhesion plaque proteins, e.g., vinculin, do not appear to play any role in assembling actin monomers at these sites on the inner surface of the sarcolemma.Immunofluorescence and immunoelectron microscopy of cardiomyocytes double‐stained with antibodies against two distant domains of connecttin (titin) filaments and other sarcomeric proteins showed that these domains of connectin filaments and myosin were synthesized almost simultaneously on large polyribosomes and/or associated immediately after the synthesis of these molecules. Connectin and myosin bands were formed after α‐actinin striations (Z bands) were seen on preformed I‐Z‐I‐like structures. The observation that the development and distribution of connectin were tightly linked with those of myosin suggests the possible role of connectin for integrating myosin filaments with the early formed I‐Z‐I complexes of myofibrils. © 1993 wiley‐Liss, Inc.
Distribution of FGF‐2 suggests it has a role in chick limb bud growth
Authors: Savage Mary Pfann , Fallon John F. , Hart Charles E. , Riley Bruce B. , Sasse Joachim , Olwin Bradley B. 
Published: February 2005

AbstractWe developed and characterized antibodies specific for FGF‐2 and used them to locate FGF‐2 during chick embryo development. A series of micrographs demonstrated the progression of FGF‐2 staining during development of the different tissues and organs. FGF‐2 was present in the ectoderm covering the entire embryo, muscle cells, nervous system, neural crest cells, and mesonephros. FGF‐2 was also present in the limb from initiation of budding through differentiation. The limb ectoderm and subjacent mesoderm showed the strongest immunostaining, with lower levels in the center of the bud. However, the distribution of FGF‐2 positive cells in the mesoderm was not homogeneous. This heterogeneity was not due to cell cycle specific distribution of FGF‐2 protein, as flow cytometric analysis showed that FGF‐2‐positive cells were distributed throughout the cell cycle. However, the amount of anti‐FGF‐2 fluorescence varied most during G1, consistent with the possibility that FGF‐2 is low after M phase and increases during G1. A bioassay was used to demonstrate FGF‐2 levels in the wing ectoderm were approximately 2.7‐fold greater than in the mesoderm. We propose that the location of FGF‐2 in the embryo is consistent with a role in epithelial‐mesenchymal interactions; in the limb bud it may prevent differentiation and permit limb outgrowth and subsequent expression of patterning events. © 1993 Wiley‐Liss, Inc.
Spatiotemporal expression of pregnancy‐specific glycoprotein gene rnCGM1 in rat placenta
Authors: Rebstock Sabine , Lucas Kurt , Weiss Martina , Thompson John , Zimmermann Wolfgang 
Published: February 2005

AbstractAs a basis towards a better understanding of the role of the pregnancy‐specific glycoprotein (PSG) family in the maintenance of pregnancy, detailed investigations are described on the expression of a recently identified rat PSG gene (rnCGM1) at the mRNA and protein levels. Using specific oligonucleotide primers, rnCGM1 transcripts were identified after reverse transcription, polymerase chain reaction, and hybridization with a radiolabelled, internal oligonucleotide. Transcripts were only found in significant amounts in placenta. In situ hybridization visualized rnCGM1 transcripts at day 14 post coitum (p.c.), in secondary trophoblast giant cells and in the spongiotrophoblast. Only those secondary giant cells lining the maternal decidua were positive. In contrast, primary giant cells did not contain rnCGM1 mRNA. At day 18 p.c., rnCGM1. transcripts were almost exclusively detectable in the spongiotrophoblast. No rnCGM1 transcripts were found in rat embryos of these two developmental stages. Rabbit antisera were generated against the amino‐terminal immunoglobulin variable‐like domain and against a synthetic peptide containing the last 13 carboxy‐terminal amino acids of rnCGM1. Bothe antisera recognized a 124 kDa protein in day 18 rat placental extracts as identified by Western blot analysis. The anti‐peptide antiserum recognized a 116 kDa protein in the serum of a 14 day p.c. pregnant rat that is absent from the sera of non‐pregnant females. Taken together, these results confirm exclusive expression of rnCGM1 in the rat trophoblast, but unlike human PSG, negligible or no expression is found in other organs, such as fetal liver or salivary glands, indicating a more specialized function of rnCGM1. Its spatiotemporal expression pattern is conducive with a potential role of PSG in protecting the fetus against the maternal immune system and/or in regulating the invasive growth of trophoblast cells. © 1993 Wiley‐Liss, Inc.
Proliferation and migration of primordial germ cells in We/We mouse embryos
Authors: Buehr Mia , McLaren Anne , Bartley Aine , Darling Susan 
Published: February 2005

AbstractWe have examined the numbers and distribution of primordial germ cells in We/We, We/+, and +/+ mouse embryos using Southern blotting to determine embryo genotypes. At early somite stages (5–7 somites: approximately 81/2 days post coitum [dpc]) there are 50 to 100 germ cells in embryos of all genotypes. The number of germ cells in We/+ and +/+ embryos then begins to increase: at later somite stages (17–19 somites: approximately 91/2 dpc) they number about 200, and by 101/2 dpc there are approximately 725We/+ and 850 +/+ germ cells. During this time, however, the number of germ cells in We/We embryos remains less than 100. At 81/2 dec, the distribution of germ cells in the hindgut endoderm is the same in all genotypes. By 91/2 dpc, 30% of We/We germ cells are found in ectopic sites (allantois and vitelline artery); germ cell distribution along the length of the hindgut appears normal, but germ cells remain confined to the floor of the gut in We/We embryos, rather than being distributed around its circumference as in the other two genotypes. By 101/2 days, the migration of We/We germ cells through the dorsal mesentery lags behind that of the other genotypes, and a larger proportion remains in the gut wall. © 1993 Wiley‐Liss, Inc.
Differential expression of muscle regulatory factor genes in normal and denervated adult rat hindlimb muscles
Authors: Voytik Sherry L. , Przyborski Maryjo , Badylak Stephen F. , Konieczny Stephen F. 
Published: February 2005

AbstractSkeletal muscle represents an excellent model system in which to examine regulatory mechanisms that modulate gene expression in the mature adult organism. Individual muscle fibers can be categorized as fast‐ or slow‐twitch based upon several physiological and molecular criteria, including metabolic enzyme activity and contractile protein isoforms. Each property can be influenced by a variety of factors such as changes in motor neuron activity or alterations in hormone levels, although the molecular pathways by which environmental factors affect gene expression remain largely unknown. As a first step in identifying potential regulators of fiber‐type diversity, the expression patterns of four basic/helix‐loop‐helix muscle regulatory factors (MRFs), referred to as MyoD, myogenin, Myf‐5, and MRF4, were examined in normal adult rat muscles which differed in their phenotypic properties. As expected, all four MRFs were expressed at detectable levels in the muscles studied. However, different muscles accumulated different proportions and combinations of MRF transcripts. For example, myogenin expression was maximally detected in slow‐twitch muscles whereas MyoD transcripts were found predominantly in muscles exhibiting a fast‐twitch phenotype. Induced phenotypic changes in two fast‐twitch muscles via denervation lead to a large and rapid increase in transcript levels of all four MRFs as early as 24 hr following denervation, with myogenin transcripts approaching 150–200‐fold higher levels than innervated contralateral muscles within 7 days. These results suggest that myogenin, as well as the other three MRFs, may be involved in both the initial establishment as well as maintenance of fiber‐type diversity in the developing organism. © 1993 Wiley‐Liss, Inc.
Expression of gap junction proteins Cx26, Cx31.1, Cx37, and Cx43 in developing and mature rat epidermis
Authors: Goliger Jeffrey A. , Paul David L. 
Published: February 2005

AbstractTo elucidate mechanisms underlying gap junction‐mediated intercellular communication in epidermal keratinocytes, we have examined the expression of four connexin genes, Cx26, Cx31.1, Cx37, and Cx43, in fetal (embryonic day 17–18), newborn (post‐natal day 0), and mature rat skin. Northern analyses of total skin RNA showed that levels of Cx26, Cx37, and Cx43 mRNAs remained relatively constant throughtout the three developmental stages examined, whereas Cx31.1 mRNA was 15–30 times more abundant in mature skin than in fetal skin. Antibodies specifically recognizing these connexin proteins were then used in conjunction with a recently described amplification technique to immunohistochemically stain sections of paraffin embedded rat tail epidermis. We show that Cx26, Cx31.1, Cx37, and Cx43 display overlapping but distinct patterns of expression within the keratinocyte cell layers of developing and mature epidermis. © 1994 Wiley‐Liss, Inc.
Stage‐ and region‐dependent chondrogenesis and growth of chick wing‐bud mesenchyme in serum‐containing and defined tissue culture media
Authors: Paulsen Douglas F. , Chen Wei‐Dang , Pang Lei , Johnson Benita , Okello David 
Published: February 2005

AbstractDuring development, limb‐bud mesenchymal cells carry out complex spatiotemporal patterns of growth and differentiation. Tissue and organ culture facilitate analysis of environmental influences on these cell behaviors, allowing their partial dissection into exogenous and endogenous components. Two factors that complicate such in vitro analyses are the heterogeneity of the cultured cells and imprecise knowledge of culture medium composition. Limb mesenchyme comprises a heterogenous cell population with important regional differences in cell type. Dividing the limb into subregions helps limit the cellular heterogeneity and using chemically defined, serum‐free medium allays concerns about medium composition. In the present study, mesenchyme from different regions along the anteroposterior and proximodistal axes of stage 21–22 and stage 23–24 chick wing buds was grown in high‐density microtiter cultures in chemically defined and in serum‐containing medium. Fourday cultures of the various regions were compared in terms of culture morphology and the accumulation of Alcian blue‐positive cartilage matrix and DNA. The results demonstrate stage‐ and region‐dependent differences in the in vitro growth, differentiation, and responsiveness of these cells. For example, mesenchyme from the distal anterior region of the wing bud exhibited lower intrinsic chondrogenic capacity and greater responsiveness to serum than other regions. Patterns of in vitro chondrogenesis also suggest that, at the stages examined, distal wing‐bud mesenchyme may be less homogeneous than has been believed. A case is made for the suitability of serum‐free medium for future in vitro studies of chick limb‐bud mesenchyme. The results are considered in relation to the process of limb development and regional expression of pattern‐related genes. © 1994 Wiley‐Liss, Inc.
Increased mesenchymal cell density accompanies induction of tropoelastin expression in developing elastic tissue
Authors: Lee Katherine A. , Pierce Richard A. , Mecham Robert P. , Parks William C. 
Published: February 2005

AbstractWe studied the differentiation of elastin‐producing fetal bovine chondrocytes to understand the regulatory processes associated with induction of elastin expression. Analysis of auricular elastic cartilage development in vivo indicated that differentiation of the prechondrogenic blastema to an elastogenic phenotype was preceded and accompanied by condensation of the mesenchymal cells. In addition, induction of elastin production was temporally and spatially linked to expression of type II collagen and proteoglycans. We assessed the influence of cell density on the induction of tropoelastin expression in pre‐elastogenic cells from developing ear buds. Tropoelastin expression was induced in prechondrogenic mesenchymal cells only if the cells were maintained at a high cellular density. In addition, high density culture upregulated tropoelastin expression in fully differentiated chondrocytes. Together these data suggest that high cell density facilitates cell:cell interactions that affect cell proliferation and influence tropoelastin expression. © 1994 Wiley‐Liss, Inc.
Barrier inhibition of a temporal neuraxial influence on early chick somitic myogenesis
Authors: Borman William H. , Yorde Donald E. 
Published: February 2005

AbstractSkeletal myogenesis in the chick embryo first occurs in the somite. Somites are transient, paired mesodermal structures adjacent to the neural tube. Somites form from the segmental plate mesenchyme at approximately 90‐min intervals. We identify somitic myogenic cells by using confocal microscopy to detect the muscle specific intermediate filament protein, desmin, in whole mount chick embryo preparations. The appearance of desmin in somitic cells does not occur at a constant interval after the somite has formed. The rate of chick somitic myogenic onset, as evidenced by detection of desmin, is approximately 1.5 times faster than the rate of somitogenesis (Borman and Yorde [1994] J. Histochem. Cytochem. 42:265–272). Somitic myogenesis does not appear to be directly linked to somitogenesis but instead may be regulated by some influence external to the somite. Here we have specifically addressed the issue of whether an impermeable barrier placed between the neuraxis and the somites can prevent the onset of somitic myogenesis. When tantalum foil barriers are placed medial to the caudalmost 3–5 somites of embryos having up to 20 somites total (stage 13), the predominant result is an inhibition of myogenic cells lateral to the barrier. Conversely, when the tantalum foil is placed medial to the caudal somites of an embryo having 21 somites (stage 14) or more, desmin is detected lateral to the barrier in most cases. There is a temporal influence originating in the neuraxis which plays a role in the onset of somitic myogenesis. Although the nature of this interaction between the neuraxis and the somites is not yet clear, we have defined a precise temporal location within the developing embryo at which this tissue interaction is taking place. © 1994 Wiley‐Liss, Inc.
Inhibition of retinal growth cone activity by specific metalloproteinase inhibitors in vitro
Authors: Sheffield J. B. , Krasnopolsky V. , Dehlinger E. 
Published: February 2005

AbstractThe developing neural retina expresses a set of extracellular proteases including plasminogen activator and gelatinases. Since neurites of retina cells cultured on fluorescent gelatin digest the substrate in their paths, we have suggested that the proteases are used by the tips of growing fibers to allow them to migrate within the mass of the tissue in vivo. In order to obtain further information about relationships between extracellular proteases and fiber growth, we have examined the effects of the specific inhibitors HS‐LFA (HS‐Leu‐Phenylala‐Ala, enantiomeric forms 1 and 2), bathophenanthroline sulfonate (BPS), phenylmethyl sulfonyl fluoride (PMSF), and relevant controls on the activity of retinal growth cones in vitro monitored by time lapse video microscopy. Of the inhibitors tested, only the two enantiomeric forms of HS‐LFA caused a reproducible cessation of both spike extensiion and filopodial processes at the growth cone ruffling, while control media had no effect. In some cases, the growth cone swelled and exhibited small protrusions. The behavior of growth cones was in sharp distinction to that of the cytoplasm of neural cells, and membrane ruffling of flat cells, which continued in activity throughout. Growth cone activity returned after several hours in the presence of the agent. BPS was toxic at concentrations above 2.5 mM. Below that, it had no effect. L‐cysteine, PMSF, and control media had no effect. The relevance of these results to the possible role of proteases in fiber outgrowth from retinal cells is discussed. © 1994 Wiley‐Liss, Inc.
Transforming growth factor‐β and bone morphogenetic protein‐2 act by distinct mechanisms to promote chick limb cartilage differentiation in vitro
Authors: Roark Eileen F. , Greer Karen 
Published: February 2005

AbstractA number of studies suggest that several members of the transforming growth factor‐β (TGF‐β) family of peptide growth factors may be involved in the regulation of cartilage differentiation. It has been previously reported that TGF‐β1 and TGF‐β2 promote the chondrogenic differentiation of chick limb mesenchymal cells in high density micromass cultures (Kulyk et al. [1989a] Dev. Biol. 135:424–430). In this study we report that chick limb mesenchymal cells express mRNA for chicken TGF‐β1, TGF‐β2, and TGF‐β3 during cartilage differentiation in vitro. In addition, the time course of their expression during cartilage differentiation is consistent with their playing a role in the initiation of this differentiation process. We also report that two members of the TGF‐β family, TGF‐β3 and bone morphogenetic protein‐2 (BMP‐2), are capable of promoting the accumulation of cartilage extracellular matrix molecules by differentiating chick limb mesenchymal cells in micromass culture. Significant differences, however, were noted between the specific effects on matrix production elicited by these two growth factors which suggest that they may be acting by distinct mechanisms to regulate cartilage matrix production. TGF‐β appears to be most effective on cells which have not yet undergone cell condensation, a critical event in early cartilage differentiation, wherease BMP‐2 is most effective after cells have condensed or differentiated. These observations suggest that TGF‐β3 and BMP‐2 may be acting in a sequential manner to regulate chick limb mesenchymal cells through the different stages of cartilage differentiation. © 1994 Wiley‐Liss, Inc.
Murine pulmonary myocardium: Developmental analysis of cardiac gene expression
Authors: Jones W. Keith , Sánchez Alejandro , Robbins Jeffrey 
Published: February 2005

AbstractLong‐standing observations that cardiac muscle exists in the walls of the pulmonary and caval veins have recently been confirmed at the molecular level (Lyons et al. [1990] J. Cell Biol. 111:2427–2436; Springall et al. [1988] Thorax 43:44–52; Subramaniam et al. [1991] J. Biol. Chem. 266:24613–24620). Using ventricle‐ and atrial‐specific riboprobes, we determined that the pulmonary myocardium exhibits an atrial pattern of cardiac‐specific gene expression. Additionally, the developmental pattern of expression was studied using a riboprobe specific to the α‐cardiac myosin heavy chain (α‐MHC) gene transcript. We find that α‐MHC gene expression is first detectable in the lung between 13.9–14.3 days post‐coitum. Extension of the α‐MHC specific hybridization signal into the pulmonary venous bed progresses through the neonatal period. The data are consistent with the hypothesis that the extension of α‐MHC gene expression into the lung occurs via the migration of atrial myoblasts into the vein during atrial septation and remodeling of the sinus venosus and pulmonary venous trunk. © 1994 Wiley‐Liss, Inc.
Pattern formation in chick feather development: Distribution of β1‐integrin in normal and scaleless embryos
Authors: Song Hee Kyung , Carver Wayne E. , Sawyer Roger H. 
Published: February 2005

AbstractWe have examined the immunolocalization of β1‐integrin during feather development in the spino‐lumbar tract of the backskin from normal and scaleless chick embryos. β1‐integrin appears during early feather development in three distinct phases which correspond to important developmental events. The first phase (5–5½ days of incubation; Hamburger and Hamilton [H.H.] stage 27) represents the period prior to the formation of dermis. During this phase, β1‐integrin antiserum labels mesenchymal cells located in the central region of the spino‐lumbar tract where the initiation site for feather development is located. The second phase (5½–7½ days of incubation; H.H. stages 28–32) corresponds to the period during which dermis is formed. The cells that make up the dermis are readily distinguished by their lack of β1‐integrin immunostaining. The third phase (7½–10 days of incubation; H.H. stages 33–36) begins with the sudden appearance of β1‐integrin in the central and lateral regions of the dermis. The pattern of β1‐integrin immunostaining in scaleless backskin becomes different from that of normal backskin during this phase. In normal backskin the dermal condensations of feather germs are not labeled with the β1‐integrin antiserum. This produces a heterogeneous immunostaining pattern very similar to the pattern seen for Type I collagen (Mauger et al. [1982] Dev. Biol. 94:93–105). In contrast, homogeneous immunostaining is observed in the dermis of scaleless backskin. The initial time of appearance, manner of appearance, and pattern of integrin expression in the third phase suggest that β1‐integrin may be involved in the stabilization of the feather pattern.We also observed the appearance of β1‐integrin on the epidermal basal cells during the time of feather follicle formation. The β1‐integrin antiserum reacts strongly with the baso‐lateral surfaces of normal basal cells, yet the basal surfaces of the scaleless basal cells are unstained. This lack of immunostaining along the basal surfaces of the scaleless basal cells may relate to the abnormal adhesion between the epidermis and dermis in scaleless backskin. © 1994 Wiley‐Liss, Inc.