bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential expression of retinoic acid receptor‐β isoforms during chick limb ontogeny
Authors: Smith Susan M. , Kirstein Isaac J. , Wang Zhong‐Shan , Fallon John F. , Kelley John , Bradshaw‐Rouse Judith 
Published: February 2005

AbstractRetinoids influence both morphogenetic events and differentiation during development of the vertebrate limb. These effects are mediated through nuclear retinoid receptors, which modulate target gene expression. We report here the cloning and characterization of three promoter‐ and splicing‐variants of the retinoic acid receptor‐β (RAR‐β) from chick. These receptor isoforms are independently expressed during limb development. RARβ2 but not RARβ1 transcripts are enriched three‐fold in the posterior limb bud, reflecting the increased RA concentrations in this region. RARβ1 transcripts are initially present throughout the limb bud mesenchyme and ectoderm, then become restricted within perichondrial regions and loose connective tissue of the limb. RARβ1 expression closely overlaps that of NCAM (neural cell adhesion molecule) and tenascin in non‐neuronal tissues. RARβ2 transcripts are present within a subset of those limb tissues which express RARβ1. In the early limb bud RARβ2 transcripts are detected in proximal limb mesenchyme and in the initial mesenchymal condensate. In older limbs RARβ2 mRNAs are abundant in cells lateral to the digit cartilage. Neither RARβ1 nor RARβ2 transcripts are associated specifically with regions of limb cell death. The differential expression and regulation of RARβ isoforms suggests these variants may have different roles in limb development. © 1995 Wiley‐Liss, Inc.
Expression of the hepatocyte growth factor gene during chick limb development
Authors: Myokai Fumio , Washio Norifumi , Asahara Yoji , Yamaai Tomoichiro , Tanda Nobuya , Ishikawa Tetsuya , Aoki Shunsuke , Kurihara Hidemi , Murayama Yoji , Saito Taiichi , Matsumoto Kunio , Nakamura Toshikazu , Noji Sumihare , Nohno Tsutomu 
Published: February 2005

AbstractIt has been shown that mirrorimage duplications of the zeugopodia and digits are formed when MRC‐5 fibroblasts producing hepatocyte growth factor (HGF) are applied to the anterior region of the chick limb bud (Yonei et al. [1993] Dev. Biol. 160:246–253). To evaluate the role of HGF in limb development, we observed the expression pattern of the HGF gene using in situ hybridization. The HGF gene was expressed in the mesoderm of the limb bud and in the central core region of mandibular arch and maxillary processes at stages 17 to 24. When both wing and leg buds begin to extend distally, the HGF gene is expressed in the mesenchymal cells, but not in the ectodermal cells and somites. Concomitant with establishment of the apical ectodermal ridge, distal mesenchymal cells of the limb bud express the HGF gene intensely with a gradient higher in the distal region. The HGF expression is later confined to the ventral and subapical mesenchyme of the limb bud, although no signal is detectable in the apical and non‐ridge ectoderm. However, signal for the c‐met proto‐oncogene encoding the HGF receptor is not detectable in the limb bud at stages 17 to 24. These results suggest that HGF produced in the limb mesoderm may be involved in initial induction and maintenance of the apical ectoderm during limb development. © 1995 Wiley‐Liss, Inc.
Synthesis and secretion of matrix‐degrading metalloproteases by human skeletal muscle satellite cells
Authors: Guérin Claude W. , Holland Paul C. 
Published: February 2005

AbstractThe expression of matrix‐degrading metalloproteases (MMPs) by human skeletal muscle satellite cells was investigated by zymography of cell culture media and by Northern blot analysis of mRNA prepared from satellite cells. Zymography in gelatin substrate gels revealed that satellite cells constitutively synthesize and secrete 72 kDa gelatinase (MMP‐2). In addition, treatment of satellite cell cultures with phorbol ester resulted in an induction of 92 kDa gelatinase (MMP‐9) activity. On casein substrate gels, little or no proteolytic activity was detectable in control or phorbol ester treated satellite cell cultures, suggesting that compared to fibroblasts, satellite cells secrete little or no interstitial collagenase (MMP‐1) or stromelysin (MMP‐3) activity. Northern blotting, however, revealed that there is detectable expression of mRNA transcripts encoding MMP‐1 in satellite cell cultures, and that increased accumulation of MMP‐1 mRNA transcripts occurs upon treatment of these cells with phorbol ester. In contrast, no constitutive, or induced expression of transcripts encoding MMP‐3 was detectable in satellite cells. These findings show that satellite cells can synthesize and secrete selected members of the MMP family and suggest that skeletal muscle cells may participate directly in remodelling of the extracellular matrix during myogenesis and the regeneration of skeletal muscle. © 1995 Wiley‐Liss, Inc.
Three‐dimensional gradients of voltage during development of the nervous system as invisible coordinates for the establishment of embryonic pattern
Authors: Shi Riyi , Borgens Richard B. 
Published: February 2005

AbstractWe are interested in the generation of endogenous electric fields associated with ionic currents driven through the vertebrate embryo by the transepithelial potential of its surface ectoderm. Using a non‐invasive vibrating electrode for the measurement of ionic current, we have provided measurements of currents traversing amphibian embryos, and a preliminary report of the internal, extracellular voltage gradient under the neural plate which polarizes the embryo in the rostral/caudal axis (Metcalf et al. [1994] J. Exp. Zool. 268:307–322). Here we complete a description of this gradient in electrical potential (ca. 10 mV/mm, caudally negative), describe a simultaneous gradient organized in the medial/lateral axis (ca. 5–18 mV/mm, negative at the margins of the neural folds), and describe their appearance and disappearance during ontogeny of the axolotl embryo. Both voltage gradients are not expressed until neurulation, and disappear at its climax. This appearance and disappearance correlates with the shunting of current out of the lateral margins of the neural folds in rostral regions of the embryo beginning at stage 15, and is not associated with a more substantial current leak from the blastopore which appears at gastrulation. A steady blastopore current is still present after neural tube formation when intra‐embryonic electric fields have been extinguished. We discuss the direct experimental tests supporting the hypothesis that these extracellular electric fields both polarize the early vertebrate embryo and serve as cues for morphogenesis and pattern. © 1995 Wiley‐Liss, Inc.
Developmental expression of fibroblast growth factor receptor‐1 (cek‐1; flg) during heart development
Authors: Sugi Yukiko , Sasse Joachim , Barron Matthew , Lough John 
Published: February 2005

AbstractPrevious work in this laboratory has indicated that fibroblast growth factor‐2 (FGF‐2; bFGF) regulates the initial stages of avian heart development in paracrine and autocrine fashion (Parlow et al. [1991] Dev. Biol. 146:139–147; Sugi et al. [1993] Dev. Biol. 157:28–37). Because these findings inferred the presence of a functional receptor for fibroblast growth factor (FGFR), we have immunochemically assessed the appearance of FGFR‐1 (cek‐1; flg) during development. Using a peptide‐generated antibody, Western blots of total embryonic proteins revealed that FGFR‐1 was barely detectable at pre‐heart stages, followed by sequential increases in relative abundance that peaked at stage 24, followed by a decline at days 7–14. Western blots of proteins from isolated embryonic hearts demonstrated a similar developmental pattern, except that FGFR‐1 expression was not decreased at later stages. The presence of FGFR‐1 mRNA was verified by reverse transcription/polymerase chain reaction (RT/PCR) amplification. Immuno‐histochemical examination revealed punctate deposits of FGFR‐1 in the precardiac endoderm at stage 6, followed by detection in the endoderm, foregut, and pre‐cardiac splanchnic mesoderm at stage 8 and in the newly formed myocardium at the heart tube stage (9/10). By stage 13, FGFR‐1 staining was observed only in the myocardium, a pattern which persisted at least until stage 30 (day 7), after which only isolated hearts were examined. After stage 30, staining was diminished in the ventricle, but not in the atrium. Staining of cardiac endothelial cells was not observed at any stage. A functional role for FGFR‐1 was indicated by experiments in which anti‐FGFR‐1, but not pre‐absorbed antiserum, retarded proliferation and multilayering of cardiogenic cells in an in vitro model of cardiac morphogenesis. © Wiley‐Liss, Inc.
Myotube driven myogenic recruitment of cells during in vitro myogenesis
Authors: Breton Muriel , Li Zhen‐Lin , Paulin Denise , Harris John A. , Rieger François , Pinçon‐Raymond Martine , Garcia Luis 
Published: February 2005

AbstractMuscular dysgenesis (mdg) is a recessive lethal mutation in the mouse which drastically affects skeletal muscle development during embryonic life. Physiologically, the disease is characterized by a complete paralysis resulting from a lack of excitation‐contraction coupling. Existing electrophysiological, biochemical, and genetic evidence shows that mdg/mdg mice express a basic alteration of L‐type voltage‐sensitive Ca2+ channels in skeletal muscle. Studies on mdg/mdg myotubes in primary culture have shown that +/+ fibroblasts or +/+ Schwann cells may fuse with them and correct their functional deficiency by genetic complementation. As the spontaneous formation of heterocaryons is thought to be an exclusive property of myoblasts, we asked whether fibroblasts may have changed their properties before fusion occurred. We used primary cells issued from sciatic nerves dissected from newborn transgenic mice carrying the pHuDes1‐nls‐LacZ transgene (Des‐LacZ cells) as non‐muscle cells. These cells were mainly fibroblasts (80%) positive for Thy 1.1 and Schwann cells positive for S100. The cultures were negative for myogenic markers (desmin, troponin T), did not form myotubes long‐term, and did not display significant activation of the muscle reporter gene (pHuDes1‐nls‐LacZ). After a few days in coculture with dysgenic or normal myotubes, the muscle reporter gene (β‐galactosidase) was detected both within dysgenic myotubes, correlating with the restoration of normal contractile activity, and normal myotubes. As well as confirming that fusion takes place, this shows that Des‐LacZ cells nuclei incorporated into recipient myotubes express their own myogenic genes. Moreover, individual mononucleated Des‐LacZ cells expressing β‐galactosidase were observed, indicating that myogenic genes were being expressed before fusion. This suggests a mechanism of myotube driven myogenic recruitment of cells during the in vitro myogenesis. Analysis of the distribution of the induced Des‐LacZ cells (positive for β‐galactosidase) in compartmentalized muscle cocultures showed that in the presence of dysgenic myotubes, these cells were equally distributed in both myotube free and enriched areas, whereas in the presence of normal myotubes, the positive cells remained in close vicinity of the myotubes. This difference could be explained by the fact that the dysgenic phenotype might include release of the induction process from its normal controls. Our results are consistent with the idea of a transcellular mechanism triggering myogenic differentiation in non‐muscle cells, and that myotubes themselves are able to drive myogenic recruitment of cells during the in vitro myogenesis. This phenomenon could be the result of either a myogenic induction in non‐muscle cells, imposing a phenotypic change, or the activation of pre‐myoblastic quiescent cells by the myotubes themselves. © 1995 Wiley‐Liss, Inc.
Expression of zfh‐4, a new member of the zinc finger‐homeodomain family, in developing brain and muscle
Authors: Kostich Walter A. , Sanes Joshua R. 
Published: February 2005

AbstractWe have identified zfh‐4, a new member of a recently recognized zinc finger‐ho‐meodomain (zfh) family of putative transcription factors. Zfh‐4 expression is prominent in developing muscle and brain. In both tissues, zfh‐4 RNA levels are highest embryonically, then decrease gradually to barely detectable levels in adults. In myogenic cell lines, far more zfh‐4 is expressed in proliferating myoblasts than in myotubes, suggesting a cellular basis for the developmental regulation observed in vivo. In contrast, zfh‐4 RNA in brain is more abundant in postmitotic cells of the marginal zone than in proliferating cells of the ventricular zone. Within the brain, zfh‐4 RNA is regionally localized: expression is highest in mid‐brain, readily detectable in hindbrain, and very low in cerebral cortex. Its patterns of expression, and its homology to known DNA binding proteins, support the idea that zfh‐4 may be a regulator of gene expression in developing brain and muscle. © 1995 Wiley‐Liss, Inc.
Mouse multidrug resistance 1a/3 gene is the earliest known endothelial cell differentiation marker during blood‐brain barrier development
Authors: Qin Ying , Sato Thomas N. 
Published: February 2005

AbstractMolecular mechanisms of endothelial cell differentiation during blood‐brain barrier (BBB) development is not well understood due to the lack of specific molecular markers. Here we describe that expression of the mouse multidrug resistance la/3 (mdrla/3) gene can be detected specifically in subsets of vascular endothelial cells associated with neural tissues at as early as embryonic day 10.5 (E10.5). This onset of mdrla/3 gene expression coincides with the previously described first appearance of morphologically distinct endothelial cells in neural tissues during BBB development. To our knowledge, the mdrla/3 gene is the earliest endothelial cell differentiation marker gene during BBB development described thus far. In addition, we have found that neither the level nor pattern of mdrla/3 gene expression in BBB endothelial cells is affected by aberrant cortical neuronal layers in mutant mouse reeler. © 1995 Wiley‐Liss, Inc.
Blood vessel formation in the avian limb bud involves angioblastic and angiotrophic growth
Authors: Brand‐Saberi Beate , Seifert Roswitha , Grim Milos , Wilting Jörg , Köhlewein Martin , Christ Bodo 
Published: February 2005

AbstractThe vasculature of the avian limb bud takes its origin from the intersomitic vessels as can be shown by ink perfusion of the embryo. While the primitive vessels form a central network in the early limb bud, an area of about 100 μm in width from the ectoderm inward remains free from lumenized vessels. However, this subectodermal avascular zone contains isolated angioblasts, which can be demonstrated by confocal laser scanning microscopy in connection with QH‐1‐staining. QH‐1‐positive cells from the avascular zone are capable of giving rise to endothelial cells when grafted ectopically into a “permissive” environment such as the dorso‐lateral paraxial mesoderm. Several grafting sites are compared regarding their permissiveness for capillary formation. In order to investigate the origin of the QH‐1‐positive angioblasts we carried out injections of DiI‐Ac‐LDL, which is specifically taken up by endothelial cells and macrophages, and found the lumenized vessels and a few isolated cells in the peripheral limb mesoderm stained. In double‐labelling studies combining DiI‐Ac‐LDL and QH‐1, it can be shown that there exists a pool of isolated angioblasts that are only QH‐1‐positive, but have not incorporated DiI‐Ac‐LDL. In contrast to the lumenized vessels in the core of the limb bud, we found that angioblasts in the avascular zone do not proliferate, as shown by proliferation studies applying the BrdU‐method to semithin sections in connection with QH‐1‐labelled parallel sections. We conclude that the vascularization of the avian limb bud is achieved by a combination of angiotrophic growth (sprouting of vessels) and angioblastic growth (recruitment of angioblasts from the limb mesoderm). © 1995 Wiley‐Liss, Inc.
Collagen fibrillogenesis in situ: Fibril segments undergo post‐depositional modifications resulting in linear and lateral growth during matrix development
Authors: Birk David E. , Nurminskaya Maria V. , Zycband Emanuel I. 
Published: February 2005

AbstractElucidating how collagen fibril growth is regulated is important in determining how tissues are assembled. Fibrils are deposited as segments. The growth of these segments is an important determinant of tissue architecture, stability, and mechanical attributes. Fibril segments were isolated from developing tendons and their structure characterized. The post‐depositional changes leading to linear and lateral growth of fibrils also were examined. Segments extracted from 14‐day chicken embryo tendons had a mean length of 29 μm. The segments were asymmetric, having a short and a long tapered end. Most of the segments were centrosymmetric with respect to molecular packing. Segments extracted from 12‐to 16‐day tendons had the same structure, but mean segment length increased incrementally due to the addition of an increasingly large population of longer segments. At 17 days of development there was a precipitous increase in segment length. The morphological data indicate that the increase in length was the result of lateral associations among adjacent segments. Analysis demonstrated that this fibril growth was associated with a significant decrease in fibril associated decorin. Using immunoelectron microscopy, decorin was seen to decrease significantly at 18 days of development. When decorin content was biochemically determined, a decrease also was observed. Decorin mRNA also decreased relative to fibrillar collagen mRNA during the same period. These data support the hypothesis that a decrease in fibril‐associated decorin is necessary for fibril growth associated with tissue maturation. Growth through post‐depositional fusion allows for appositional and intercalary growth and would be essential for normal development, growth, and repair. © 1995 Wiley‐Liss, Inc.
Cyclopamine, a steroidal alkaloid, disrupts development of cranial neural crest cells in Xenopus
Authors: Dunn Michael K. , Mercola Mark , Moore David D. 
Published: February 2005

AbstractCyclopamine is a steroidal alkaloid which causes limb and craniofacial defects in many vertebrate species. We have used Xenopus laevis as a model system to characterize the defects caused by cyclopamine at the cellular level. The most dramatic consequence of cyclopamine treatment in the Xenopus embryo is a defect in formation of craniofacial cartilage. Much of this cartilage is absent in treated animals. As in avian and mammalian species, Xenopus craniofacial cartilage is derived primarily from cells of the cranial neural crest. Grafting experiments show that development of the cartilaginous derivatives of the cranial neural crest is impaired after cyclopamine treatment, and this is at least partially due to a direct effect on presumptive crest cells. A culture system was used to determine the cellular response to the drug. Cyclopamine did not block the initial emigration of cells from a neural plate explant. However, cell death is seen in treated cultures after 4 days. Trunk neural crest cells and transformed cell lines are resistant to cyclopamine. We therefore conclude that cyclopamine specifically causes death of cranial neural crest cells and that lethality is likely to account for the teratogenic effects of this compound. © 1995 Wiley‐Liss, Inc.
Retinoic acid‐induced cell death in the wound epidermis of regenerating zebrafish fins
Authors: Ferretti Patrizia , Géraudie Jacqueline 
Published: February 2005

AbstractPrevious work has shown that treatment with retinoic acid (RA) can induce malformations in regenerating pectoral and caudal fins. RA‐treated regenerates are narrower than unamputated and regenerated control fins because of a decrease in the distance between rays, and either partial or total fusion of some of them. In order to tackle the issue of how RA induces its teratogenic effects on regenerating fins, and which cell types may be specifically affected by RA, we have examined the cellular changes occurring in early regenerates following treatment with retinoids. The work presented here shows for the first time that RA induces significant apoptosis in the wound epidermis, but not in the mesenchyme, of a regenerating appendage, besides inhibiting blastema development as reported in other species. We also show that RA does not retard regeneration by inhibiting accumulation of blastemal cells, but probably by impairing their ability to migrate distal to the amputation plane. This effect is rapidly reversed by discontinuing the treatment, and within 24 hr of removing the drug, blastema development is well advanced. By this time the teratogenic effects induced by RA are already apparent. A correlation between the length of the apical ectodermal ridge (AER) and the number of digits formed has been demonstrated in developing limb buds. We therefore suggest that RA‐induced patterning abnormalities in regenerating fins are the consequence of a reduction in the size of the wound epidermis, due to increased cell death, which would affect patterning of the underlying mesenchyme. © 1995 Wiley‐Liss, Inc.
Expression of two new protein isoforms of the neurofibromatosis type 1 gene product, neurofibromin, in muscle tissues
Authors: Gutmann David H. , Geist Robert T. , Rose Kamala , Wright Douglas E. 
Published: February 2005

AbstractThe neurofibromatosis type 1 (NF1) gene encodes a tumor suppressor protein, termed neurofibromin, which is expressed predominantly in neurons, Schwann cells, oligodendrocytes, and leukocytes. There are at least three isoforms of neurofibromin produced by the alternative use of exons 23a and 48a. Previously we described the identification of an NF1 mRNA isoform containing an additional 54 nucleotides from exon 48a (type 3 NF1 ) in human skeletal, cardiac and smooth muscle tissues by reverse‐transcribed (RT)‐PCR. To extend our initial observations, we have produced high titer chicken IgY antibodies which specifically recognize this muscle‐specific neurofibromin isoform. An NF1 cDNA was generated containing human exon 48a sequences and expressed as a fusion protein in bacteria. The muscle‐specific neurofibromin antibodies detected this exon 48a fusion protein by Western immunoblotting. Immunoprecipitation using these type 3 neurofibromin antibodies also specifically detected a 250 kDa protein in human and rat muscle tissues. Type 3 neurofibromin was found in rat heart and muscle, but not in live, brain, kidney or spleen with levels of expression declining after postnatal day 7. Expression of total NF1 RNA during rat embryonic development was detected at high levels in E15 heart, tongue, and limb bud. In addition, using type 2 neurofibromin‐specific antibodies, the existence of a fourth isoform of neurofibromin (type 4 neurofibromin) containing both exon 23a and 48a sequences was demonstrated in rat heart muscle tissues. The identification of two muscle‐specific isoforms of neurofibromin expands our definition of this important tumor suppressor protein and suggests additional roles for neurofibromin in muscle development and differentiation. © 1995 Wiley‐Liss, Inc.