bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on insulin‐like growth factor‐I and insulin in chick limb morphogenesis
Authors: Dealy Caroline N. , Kosher Robert A. 
Published: February 2005

AbstractThe apical ectodermal ridge (AER) promotes the proliferation and directed outgrowth of the subridge mesodermal cells of the developing limb bud, while suppressing their differentiation. Insulin‐like growth factor‐I (IGF‐I) and its receptor are expressed by the subridge mesodermal cells of the chick limb bud growing out in response to the AER, and specific insulin receptors are present in the limb bud during its outgrowth. To study the possible roles of IGF‐I and insulin in limb outgrowth, we have examined their effects on the morphogenesis of posterior and anterior portions of the distal tip of stage 25 embryonic chick wing buds subjected to organ culture in serum‐free medium in the presence or absence of the AER and limb ectoderm. The distal mesoderm of control posterior explants lacking an AER or all limb ectoderm ceases expressing IGF‐I mRNA, exhibits little or no proliferation, fails to undergo outgrowth, and rapidly differentiates. Exogenous IGF‐I and insulin promote the outgrowth and proliferation and suppress the differentiation of distal mesodermal cells in posterior explants lacking an AER or limb ectoderm, thus mimicking at least to some extent the outgrowth promoting and antidifferentiative effects normally elicited on the subridge mesoderm by the AER. Furthermore, IGF‐I and insulin‐treated posterior explants exhibit high IGF‐I mRNA expression, indicating that IGF‐I and insulin maintain the expression of endogenous IGF‐I by the subridge mesoderm. We have also found IGF‐I and insulin can affect the morphology and activity of the AER. When the posterior portion of the wing bud tip is cultured with the AER intact in control medium, on day 4–5 the AER flattens, ceases expressing high amounts of the AER‐characteristic homeobox‐containing gene Msx2, and concomitantly an elongated cartilaginous element differentiates in the subridge mesoderm. In contrast, in the presence of exogenous IGF‐I or insulin the AER of such explants does not flatten, continues expressing high amounts of Msx2, and the subridge mesoderm remains undifferentiated and proliferative. Thus, exogenous IGF‐I and insulin maintain the thickness of the AER and sustain its expression of Msx2, while sustaining the anti‐differentiative effect normally elicited on the subridge mesoderm by a thickned functional AER. Notably, we have also found that exogenous IGF‐I and insulin induce the formation of a thickened ridge‐like structure that expresses high amounts of Msx2 from the normally thin distal anterior ectoderm of the limb bud, while promoting dramatic outgrowth and proliferation of the anterior mesoderm, which normally undergoes little outgrowth or proliferation. These studies provide support for the hypothesis that endogenous IGF‐I and insulin may be involved in promoting the outgrowth and suppressing the differentiation of limb mesoderm in response to the AER, and also in regulating and/or maintaining at least some aspects of AER activity. © 1995 Wiley‐Liss, Inc.
Mesenchymal stem cells reside within the connective tissues of many organs
Authors: Young H. E. , Mancini M. L. , Wright R. P. , Smith J. C. , Black A. C. , Reagan C. R. , Lucas P. A. 
Published: February 2005

AbstractPrevious studies have noted the presence of mesenchymal stem cells located within the connective tissue matrices of avian skeletal muscle, dermis, and heart. In these studies, clonal analysis coupled with dexamethasone treatment revealed the presence of multiple populations of stem cells composed of both lineage‐committed progenitor mesenchymal stem cells and lineage‐uncommitted pluripotent mesenchymal stem cells. The present study was undertaken to assess the distribution of these stem cells in the connective tissues throughout various regions of the body. Day 11 chick embryos were divided into 26 separate regions. Heart, limb skeletal muscle, and limb dermis were included as control tissues. Cells were harvested enzymatically and grown using conditions optimal for the isolation, cryopreservation, and propagation of avian mesenchymal stem cells. Cell aliquots were plated, incubated with various concentrations of dexamethasone, and examined for differentiated phenotypes. Four recurring phenotypes appeared in dexamethasone‐treated stem cells: skeletal muscle myotubes, fat cells, cartilage nodules, and bone nodules. These results suggest that progenitor mesenchymal stem cells and putative pluripotent mesenchymal stem cells with the potential to form at least four tissues of mesodermal origin have a widespread distribution throughout the body, being located within the connective tissue compartments of many organs and organ systems. © 1995 Wiley‐Liss, Inc.
Examination of fibronectin distribution and its sources in the regenerating newt limb by immunocytochemistry and in situ hybridization
Authors: Nace Jackie D. , Tassava Roy A. 
Published: February 2005

AbstractUsing monoclonal antibodies (mAbs) reactive to newt limb regenerates, we hope to gain insight into the identity and function of regeneration significant molecules. mAb MT4 (matrix 4) identifies an extracellular matrix (ECM) protein that is strongly up‐regulated first in the distal stump and then in the blastema during regeneration. Within the first 24 hr after amputation the MT4 antigen is localized to an acellular space beneath the wound epithelium, and first appears in the basal cells of the wound epithelium between days 5 and 7. At mid‐bud blastema stages, the MT4 antigen is homogeneously distributed as thin fibers in the blastema ECM, and is later largely restricted to the distal tip of the blastema and the areas of cartilage condensation. After extraction and immunoblotting, the MT4 antigen was observed as three reduced species of Mr 225, 250, and 260. Taken together, the immunoblot and immunocytochemistry results suggested that mAb MT4 recognized newt fibronectin (FN). Sequence from a cDNA (NvFN.10) obtained by screening a newt blastema cDNA expression library with mAb MT4 conclusively identified the MT4 antigen as FN. To further investigate the expression of FN in regeneration, cDNA NvFN.10 was used to construct a riboprobe and in situ hybridization was done. In the unamputated limb only a few scattered cells expressed the FN gene. Within the first 3 days after amputation strong hybridization signal was observed in the basal cells of the wound epithelium. Most of the stump cells that dedifferentiated and accumulated beneath the wound epithelium at 7 days expressed the FN gene, while the basal cells of the wound epithelium maintained their expression. At mid‐ and late‐bud blastema stages the vast majority of the blastema cells were strongly expressing the FN gene, but the wound epithelial cells now showed only weak FN transcription. Thus initially FN comes from the plasma. Then FN is synthesized by both the wound epithelium and mesenchyme. Finally, at blastema stages FN is produced primarily by the mesenchyme. The expression pattern of FN throughout regeneration suggests that this glycoprotein has roles in wound epithelial and mesenchymal cell migration and mesenchymal cell proliferation and differentiation. © 1995 Wiley‐Liss, Inc.
Angiogenic potential of the avian somite
Authors: Wilting Jörg , Brand‐Saberi Beate , Huang Ruijin , Zhi Qixia , Köntges Georgy , Ordahl Charles P. , Christ Bodo 
Published: February 2005

AbstractWe have studied the angiogenic potential of the unsegmented paraxial mesoderm and epithelial somites of the trunk with homotopical grafts between quail and chick embryos. Quail endothelial cells of the grafts were stained with the QH‐1 antibody after 1–6 days of reincubation. The unsegmented paraxial mesoderm and all parts of the epithelial somite were found to contain angioblasts which develop into QH‐1 positive endothelial cells. These cells are incorporated into the lining of the host's blood vessels such as the perineural vascular plexus and the dorsal branches of the aorta. There is a certain preference as concerns the location of endothelial cells derived from different parts of the somites. Angioblasts from ventral somite halves are mainly found in ventrolateral blood vessels. Those from dorsomedial quadrants form vessels in the dermis of the back, and those from dorsolateral quadrants can be found in the ventrolateral body wall and the wing. With the exception of the dorsal perineural vascular plexus, angioblasts do not cross the median plane of the body. This shows that, although angioblasts migrate extensively, there is bilaterality of the vascular system in the trunk. It remains to be studied whether the notochord plays a role in the establishment of this bilaterality. © 1995 Wiley‐Liss, Inc.
Experimental analysis of Msx‐1 and Msx‐2 gene expression during chick mandibular morphogenesis
Authors: Mina Mina , Gluhak Jelica , Upholt William B. , Kollar Edward J. , Rogers Barbara 
Published: February 2005

AbstractHomeobox‐containing genes are thought to be involved in regulating pattern formation in a variety of tissues during embryogenesis. We have examined the expression of the homeobox‐related genes Msx‐1 and Msx‐2 during the development of the chick mandibular arch. Northern blot hybridization indicates that transcripts for both Msx‐1 (1.6 Kb) and Msx‐2 (3 Kb) are present in the mandibular arch as early as stage 18. The levels of both transcripts in the whole mandible decrease as cartilage is formed in vivo and in vitro. Using in situ hybridization, transcripts of Msx‐1 were localized in high amounts to the mesenchyme of the mesial tips of the arches. Msx‐2 transcripts were localized in high amounts to medial regions of the arches. Little or no hybridization of either probe was detected in the chondrogenic and myogenic regions of the arches. Transcripts of both genes were also excluded from calcified bone and cartilage. Our results further demonstrate that the mesial tip mesenchyme expressing Msx‐1 includes areas of highly proliferative cells and has in vitro chondrogenic potential. The region of mesenchymal cells expressing the Msx‐2 gene overlap with areas of developmentally programmed cell death which also contain very few proliferative cells and lack chondrogenic potential in vitro. These results are consistent with the possibility that Msx‐1 may be involved in the outgrowth of the mandibular arch and Msx‐2 may be involved in both developmentally programmed cell death and delineating the non‐chondrogenic region of the medial part of the mandibular arch. © 1995 Wiley‐Liss, Inc.
Transient and continuous expression of NADPH diaphorase in different neuronal populations of developing rat spinal cord
Authors: Wetts Richard , Phelps Patricia E. , Vaughn James E. 
Published: February 2005

AbstractNitric oxide is a novel intercellular messenger whose role in neuronal development is not yet known. As a first step toward elucidating its developmental function, we examined the pattern of NADPH diaphorase histochemical staining, an indicator of the presence of nitric oxide synthase, in the rat spinal cord at pre and postnatal ages. Some types of neurons expressed diaphorase activity transiently during development. For example, a subset of somatic motor neurons, located in the ventrolateral corner of a few caudal segments of the cervical spinal cord, were diaphorase‐positive beginning on E15, but gradually became diaphorase‐negative by birth. In contrast, other spinal neurons expressed diaphorase activity continuously from development into adulthood. Preganglionic autonomic motor neurons became diaphorase‐positive early in their development, as they were migrating toward their adult positions. Other spinal neurons, such as those in superficial dorsal horn, first expressed diaphorase relatively late in their development, after reaching their final location. The transient expression in some cell types, as well as the early expression in others, suggest that nitric oxide may have an important role(s) during development, which may differ from its functions in the adult nervous system. © 1995 Wiley‐Liss, Inc.
MyoD protein accumulates in satellite cells and is neurally regulated in regenerating myotubes and skeletal muscle fibers
Authors: Koishi Kyoko , Zhang Ming , McLennan Ian S. , Harris A. John 
Published: February 2005

AbstractMyoD belongs to a family of helix‐loop‐helix proteins that control myogenic differentiation. Transfection of various non‐myogenic cell lines with MyoD transforms them into myogenic cells. In normal embryonic development MyoD is upregulated at the time when the hypaxial musculature begins to form, but its role in the function of adult muscle remains to be elucidated. In this study we examined the cellular locations of MyoD protein in normal and abnormal muscles to see whether the presence of MyoD protein is correlated with a particular cellular behaviour and to assess the usefulness of MyoD as a marker for satellite cells. Adult rats were anaesthetised and their tibialis anterior or soleus muscles either denervated, tenotomised, freeze lesioned, lesioned and denervated, or lesioned and tenotomised. At various intervals after the operations the rats were killed and their muscles removed, snap frozen, and sectioned with a cryostat along with muscles from unoperated neonatal and adult rats. The sections were processed for immunohistochemistry using a rabbit affinity‐purified antibody to recombinant MyoD. MyoD proved to be an excellent marker for active satellite cells; satellite cells in neonatal and regenerating muscles contained high levels of MyoD protein. MyoD positive cells were not observed in the muscles of old adults, in which the satellite cells are fully quiescent. MyoD immunoreactivity was rapidly lost from satellite cell nuclei after they fused into myotubes and was not detected in either sub‐synaptic or non‐synaptic nuclei of mature fibers. Denervation, and to a lesser extent tenotomy, of lesioned muscles induced expression of MyoD in myotubal nuclei. Denervation of normal muscles also upregulated MyoD in muscle fiber nuclei, an effect which was maximal after 3 days. We conclude that MyoD protein is neurally regulated in both myotubes and muscle fibers. © 1995 Wiley‐Liss, Inc.
Basal lamina development in chicken muscle spindles
Authors: Maier Alfred , Mayne Richard 
Published: February 2005

AbstractThe development of basal laminas was examined in immunohistochemical sections of chicken leg muscle spindles from embryonic day (E) 13 to 8 weeks postnatal. Fragments of basal laminas as seen with immunostaining for isoforms of laminin were already observed in E6 muscles. When clusters of intrafusal myotubes were first recognized at E13‐14, they were surrounded by basal laminas which were incomplete both in terms of coverage and molecular composition. More mature basal lamina tubes individually enclosed young myofibers at E18. Afterents made contact with myotubes, synaptic portions of basal laminas at myosensory junctions reacted strongly with antibodies against s‐laminin and chondroitin sulfate proteoglycan, while extrasynaptic portions were negative or reacted only weakly. At synaptic basal laminas of neuromuscular junctions heparin sulfate proteoglycan and s‐laminin became prominent after E16. Contrary to the early presence of basal lamina proteins around intrafusal fibers, initial deposition of basal lamina proteins in the outer spindle capsule was not recognized until E17‐18, and significant amounts were not detected until postnatal week 1. Unlike intrafusal basal laminas, capsular basal laminas developed no distinct specialized regions; however, molecular compositions of intrafusal and capsular basal laminas were similar. © 1995 Wiley‐Liss, Inc.
Clusterin expression within skin correlates with hair growth
Authors: Seiberg Miri , Marthinuss Jeffrey 
Published: February 2005

AbstractClusterin/TRPM‐2 is a sulfated glycoprotein that is expressed in many tissues. Independently cloned and isolated by several laboratories, it bears many names, and has been shown to be involved in many processes. These include cell‐cell adhesion and aggregation, inhibition of complement cytolysis, programmed cell death and apoptosis, tissue remodeling, and terminal differentiation. The hair follicle undergoes cycles of growth, regression, and rest, which involve both tissue remodeling and programmed cell death. To identify whether clusterin expression is involved in hair growth and cycling, we studied the expression of clusterin throughout the hair cycle. We demonstrate that clusterin is expressed during the growth phase of the hair cycle. We found no correlation between clusterin expression and the apoptotic regression of the hair follicle. Using immunohistochemistry we localized clusterin to the inner root sheath of the follicle. This suggests that clusterin might be involved in the morphogenesis and differentiation of the hair follicle. We propose that clusterin has a role in the maintenance of the layered structure of the hair follicle, and in the interactions between the inner root sheath and both the outer root sheath and the hair shaft. © 1995 Wiley‐Liss, Inc.
FGF‐2 mRNA and its antisense message are expressed in a developmentally specific manner in the chick limb bud and mesonephros
Authors: Savage Mary Pfann , Fallon John F. 
Published: February 2005

AbstractFGF‐2 protein is present in the ectoderm and mesoderm of the developing chick limb bud. Its importance has been shown by the ability of ectopically applied FGF‐2 to replace the apical ectodermal ridge, allowing complete outgrowth and subsequent pattern formation of the limb bud. The first goal of this study was to determine whether FGF‐2 mRNA was present in the same ectodermal and mesodermal regions of the chick embryo as FGF‐2 protein. FGF‐2 also has an antisense message that is convergently transcribed from the opposite DNA strand (Kimelman and Kirschner [1989] Cell 59:687–696; Volk et al. [1989] EMBO J. 8:2983–2988). The second goal was to demonstrate the expression and distribution of the antisense message. Using RNAse protection assays we detected a full length protected fragment that corresponds to chick embryo FGF‐2 mRNA, and a partially protected fragment that corresponds to the antisense message. We used in situ hybridization to show that FGF‐2 mRNA was present in the ectoderm and subjacent mesoderm of the chick wing bud. FGF‐2 mRNA was also present in body ectoderm and undifferentiated mesoderm throughout the embryo, and in muscle cells, dorsal neural tube, and mesonephros. In situ hybridization also revealed evidence for the presence of the natural antisense message in the embryo in most, but not all, of the same regions as the FGF‐2 mRNA. FGF‐2 mRNA and its antisense message colocalized in undifferentiated limb mesoderm; however, antisense message was not detected in differentiated muscle or cartilage. It is important to note that FGF‐2 mRNA was always present in the mesonephros but that the antisense message was never observed in the mesonephros, thereby providing an internal control for non‐specific signal. Although little is known about its function, Kimelman and Kirschner ([1989] Cell 59:687–696) proposed that the antisense message may increase turnover of FGF‐2 mRNA. When we compared the in situ hybridization data of both mRNAs with levels of FGF‐2 protein (Savage et al. [1994] Dev. Dyn. 198:159–170), interesting tissue specific patterns emerged that support this hypothesis. © 1995 Wiley‐Liss, Inc.
Expression pattern of the murine LIM class homeobox gene Lhx3 in subsets of neural and neuroendocrine tissues
Authors: Zhadanov Alexander B. , Bertuzzi Stefano , Taira Masanori , Dawid Igor B. , Westphal Heiner 
Published: February 2005

AbstractMurine Lhx3 cDNA isolated from the mouse pituitary cDNA library encodes a LIM‐type homeodomain protein that contains two tandemly repeated LIM domains and the homeodomain. The identities of predicted amino acid sequences between the mouse Lhx3 and Xenopus Xlim‐3 genes are 80, 95, and 97% in the LIM domains 1 and 2, and the homeodomain, respectively, and 84% in the entire protein. 5′‐RACE procedures and genomic cloning revealed that two distinct N‐terminal sequences arise from two different exons 1a and 1b. Exon 1a encodes a sequence similar to that of Xlim‐3, whereas exon 1b encodes a different N‐terminus. It is likely that there are two transcription initiation sites in the Lhx3 gene. The Lhx3 transcripts were detected by whole mount in situ hybridization as early as day E9.5 post coitum in Rathke's pouch and the closing neural tube. During subsequent development, Lhx3 expression was observed in the anterior and intermediate but not in the posterior lobes of the pituitary, and in the ventral hindbrain and spinal cord. Northern blot analysis of adult tissues showed that Lhx3 mRNA persists in the pituitary. The expression pattern of Lhx3 is well conserved between Xenopus and mouse, underscoring the functional importance of this gene as a regulator of development. A number of established cell lines of pituitary origin express Lhx3 and therefore constitute a useful tool for further study of Lhx3 gene function. © 1995 Wiley‐Liss, Inc.
Re‐programming of expression of the KGFR and bek variants of fibroblast growth factor receptor 2 during limb regeneration in newts (Notophthalmus viridescens)
Authors: Poulin Matthew L. , Chiu Ing‐Ming 
Published: February 2005

AbstractWe have previously shown, by in situ hybridization, that fibroblast growth factor receptor 2 (FGFR2) is present in the basal layer of wound epithelium during limb regeneration in newts (Notophthalmus viridescens ). In contrast, FGFR1 expression is observed throughout the blastema mesenchyme but is distinctly absent from the wound epithelium (Poulin et al. [1993] Development 119:353–361). Sequence analysis revealed that we have isolated both the KGFR and bek variants of FGFR2. These two variants differ only in the second half of the last of their three (or two) Ig‐like domains. In this report, we show the expression patterns of FGFR2 variants during limb regeneration by in situ hybridization. During the pre‐blastema stages of regeneration, FGFR2 expression was observed in the basal layer of the wound epithelium and in the cells of the periosteum. The wound epithelial hybridization was observed when the KGFR‐specific probe was used while the bek ‐specific probe hybridized to mRNA in the cells of the periosteum. As regeneration progresses to the blastema stages, KGFR expression continued to be observed in the basal layer of the wound epithelium with additional hybridization seen in the blastema mesenchyme closely associated with the bisected bones. The bek ‐specific hybridization pattern observed at this stage corresponds specifically to the mesenchymal hybridization. In the differentiation stages of regeneration, the mesenchymal expression of FGFR2 becomes restricted to the cells of the condensing cartilage and later to the perichondrium. Interestingly, there appears to be a dorsoventral gradient of the expression of both KGFR and bek variants of FGFR2, which are opposite each other at the later stages of regeneration. Thus, re‐programming of expression of the two FGFR2 variants is required during the initial wound closure of limb regeneration. Remarkably, the expression patterns of KGFR and bek mimic those observed in the mouse limb bud during early embryonic development (Orr‐Urtreger et al. [1993] Dev. Biol. 158:475–486). Moreover, our results suggest that the two FGFR2 variants have distinct roles in limb regeneration. Further investigation regarding the potential sources of the FGF ligands will help establish the roles that FGFs and FGFRs play in limb regeneration. © 1995 Wiley‐Liss, Inc.