摘要:

AbstractInterspecific grafting experiments between chick and quail embryos were carried out to investigate the differentiation capacities of myoblasts from different development stages. Grafts consisted of 3.5‐day‐old embryonic quail dermomyotomes isolated from the cranial level, 7‐ to 10‐day‐old and 16‐day‐old embryonic quail pectoralis muscles, 15‐day‐old postnatal quail pectoralis muscle, and 3‐ to 10‐day‐old embyonic quail cardiac and gut muscles. Grafts were implanted into 2‐day‐old chick embryos in place of the dorsal halves of somites from the prospective wing level. After implantation of dermomyotome fragments, we observed that quail cells participated in trunk and limb musculature. After implantation of 7‐ to 10‐day‐old embryonic muscle, quail cells were rarely found in the limb but systematically took part in the formation of trunk muscles. All these capacities were totally lost in 16‐day‐old embryonic and 15‐day‐old postnatal muscles. After implantation of nonsomitic derivatives such as embryonic cardiac and gut muscles, implanted cells never participated either in wing or trunk musculature. After dermomyotome, embryonic muscle, and gut implantation, quail cells were capable of invading the dermis and aggregating into feather germs. Our results extend those previously reported and indicate that somitic myogenic derivatives which do not migrate in the normal course of embryogenesis have migratory potentialities and are able to give rise to axial muscles. All these potentialities are lost as myogenesis pr

ISSN:1058-8388    

DOI:10.1002/aja.1002010202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

Abstractαvintegrin subunit can dimerize with different β subunits to form receptors for several matrix proteins. The function of these receptors in vivo is still largely unknown. We examined the localization of αvintegrin during mouse development and showed that its distribution is dynamically regulated in the glia of the central nervous system and in skeletal muscle. Immunoreactivity in the neural tube was firstly localized at embryonic day 10.5 (E10.5) around cell bodies lining the lumen and along tiny fibers extending towards the outer margin. At E12.5 αvdistribution follows the highly defined pattern of the radial glia: fascicles of immunoreactive fibres form parallel palisades, in particular along the hindbrain and the spinal cord. At E15.5, although with weaker intensity, αvwas still detectable in radial glia fibres, and it codistributed with glial fibrillary acidic protein positive fascicles. After birth (P8) αvimmunoreactivity in the brain and spinal cord decreased dramatically, but remained high in the radial glia of the cerebellum. In adult mice αvreactivity in the central nervous system disappeared. During myogenesis αvappears at E10.5 in myotomal cells and from E12.5 αvwas evident in myoblasts and in myotubes. In the developing skeletal muscle of E15.5 embryos, immunoreactivity became more concentrated in the apical portion of the myotubes. In adult striated muscle the amount of αvsubunit dramatically declined and immunostaining was no longer detectable. During development, αvwas weakly evident in other sites including heart and endothelia of blood vessels, mesonephric tubula, smooth muscle of the digestive tract, and bronchia. Comparative analysis of the localization of αv, α3, and α5integrin subunits indicated that αvhas a unique and highly regulated distribution pattern. The distribution in the nervous system is consistent with a role of αvin neuron‐glia interaction during the organization of the neuronal layers in the brain cortex and in the cerebellum. Moreover, αvis likely to be involved in the myotendinous junction during embryonic life, suggesting a dual functional role of this integrin in muscle and nervous tissue. © 1

ISSN:1058-8388    

DOI:10.1002/aja.1002010203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractN‐cadherin cDNA was cloned from a zebrafish embryonic cDNA library. Analysis of the deduced amino acid sequence of this moleoule (ZN‐eadherin) revealed a high degree of homology to N‐cadherins of other species, except that its pre‐sequence is considerably shorter. Nevertheless, following transfection into chinese hamster ovary (CHO) cells, the expressed protein was functionally active, namely participated in calcium‐dependent intercellular interactions. Moreover, ectopic over‐expression of ZN‐cad‐herin, following mRNA microinjection into 2–4 cell embryos, caused microaggregation and uneven segregation of deep cells, resulting in distorted embryos. Developmental Northern and Western blot analyses indicated that both the mRNA and the protein first appear at gastrulation. In‐situ hybridization showed that ZN‐cadherin mRNA was initially present in all deep cells, and later became restricted to various epithelial and neural tissues. Whole‐mount immunostaining indicated that while ZN‐cadherin was already present at 50% epiboly, it became associated with cell junctions only 4–5 h later. In developing somites ZN‐cadherin expression was prominent but transient. High levels of the protein were detected in epithelial somites and its expression was apparently down regulated concomitantly with the onset of myoge

ISSN:1058-8388    

DOI:10.1002/aja.1002010204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe ontogeny of the embryonic and fetal lung involves complex interactions between epithelial and mesenchymal primordia which require a specific program of gene regulation and signal transduction. Past studies in our laboratory using congenic mouse strains indicate that one or more genes which map to the H‐2 region of chromosome 17 regulate the rate of lung morphogenesis, defined in this context as differentiative heterochrony among strains. Since hormones and growth factors are the messengers of morphogenesis, it was logical to propose that tumor necrosis factor‐α (TNF‐α), a well‐characterized cytokine whose gene maps to the D‐region of the H‐2 complex, is a putative mediator of lung morphogenesis. We investigated this proposition using immunochemical methods and a serumless, chemically defined in vitro model system. Our results demonstrate that: (1) TNF‐α has a specific spatiotemporal localization, in vivo and in vitro; (2) TNF‐α receptor, in vivo and in vitro, is localized throughout the embryonic lung; (3) TNF‐α supplementation in vitro of embryonic lung primordia has a marked dose‐dependent, stimulatory effect on branching morphogenesis and surfactant‐associated protein (SP‐A) expression; (4) multiple immunoreactive proteins, including 17, 26, and 68 kDa species, are expressed during development in vivo, and a subset of these are expressed in vitro; and (5) both time‐ and glucocorticoid‐dependent changes occur in the in vivo expression pattern of TNF‐α immunoreactive proteins after 4 and 7 days in vitro, including the up‐regulation of a novel 40 kDa protein. Given that glucocorticoids (CORT) regulate TNF‐α expression and TNF‐α's ability to stimulate pulmonary morphodifferentiation and histodifferentiation, we conclude that TNF‐α is an autocrine/paracrine pulmonary cytokine, probably a component of the lung morphogenesis pat

ISSN:1058-8388    

DOI:10.1002/aja.1002010205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have made a detailed analysis of cell behaviour using high resolution timelapse microscopy of the earliest cellular interactions taking place during morphogenesis of the notochord and somites in intact teleost embryos. Notochord formation is typified by active intercalation of paraxial mesenchyme cells into the lateral surfaces of the primordium. Following this recruitment phase, complete immiscibility develops between cells of the notochord and the presomitic mesenchyme. Dorso‐ventral and rostro‐caudal expansion of the notochord is characterised by translocation of cells within dorsoventral planes of section and is supported by elongation of the remaining cells and reduction in width across its latero‐medial axis. A lateral pallisading of paraxial mesenchyme against the lateral aspects of the notochord precedes overt segmentation. Intersomitic furrows form by localised de‐adhesion at small foci at the nascent intersomitic planes, which are consolidated by coalescence of such areas by de‐adhesion to produce the interface. It is not possible to predict precisely where cells would initiate de‐adhesion since there is a stochastic element to the phenomenon. Once formed, boundaries between somites are stable and provide no opportunity for mixing, except across the first formed furrow, which disintegrates at the 4‐6 somite stage. The first ten somites form at a constant rate of 2.3 somites/hr, during which time we recorded constant relative displacement of the segmental plate against the rostro‐caudally elongating notochord. Unlike teleost epiboly and gastrulation, no large‐scale movements of individual cells can be detected during elaboration of the embryonic axis. © 19

ISSN:1058-8388    

DOI:10.1002/aja.1002010206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractBone morphogenetic proteins BMP‐4 and BMP‐2 are closely‐related members of the transforming growth factor‐β superfamily that have been implicated in signalling in a number of developmental systems. To determine whether they could be involved in the epithelial‐mesenchymal interactions that control face development, we mapped the distribution ofBmp‐4andBmp‐2gene transcripts in the developing chick facial primordia. At stages when primordia were becoming established,Bmp‐4transcripts were present in specific regions of epithelium in all facial primordia, but were undetectable in the mesenchyme.Bmp‐4transcripts appeared subsequently in specific regions of mesenchyme at the distal tips of the primordia. This mesenchymal expression first appeared in the frontonasal mass and then, in turn, in the lateral nasal processes, the maxillary primordia and the mandibular primordia. There was a complex relationship between domains of epithelial and mesenchymalBmp‐4expression, and at many sites there was an inverse correlation between epithelial and mesenchymalBmp‐4expression.Bmp‐2transcripts were found in the epithelium and mesenchyme of the maxillary and mandibular primordia at early stages in facial development.Bmp‐2transcripts appeared in the frontonasal mass and lateral nasal processes at later stages, with epithelial expression preceding mesenchymal expression. In general, mesenchymalBmp‐2expression was associated with overlying epithelialBmp‐2expression. The domains ofBmp‐4expression overlapped with those ofBmp‐2, but detailed examination showed that there was no precise correlation between the expression patterns of the two genes. Indeed, in some places theBmp‐4andBmp‐2expression domains were complementary. The expression of theBmp‐4andBmp‐2genes in the epithelium and distal mesenchyme of the facial primordia suggests that BMP‐4 and BMP‐2 may be involved in the epithelial‐mesenchymal interactions that control outg

ISSN:1058-8388    

DOI:10.1002/aja.1002010207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTranscription mapping and nucleotide sequence analysis reveal that the genomic region of theDrosophila Ras1gene contains a cluster of three closely localized genes. A gene termedRlb1is located nearby and upstream ofRas1, and is oriented in the opposite polarity relative toRas1. In addition, a third gene termedRlc1, is found at a very close proximity downstream toRlb1.Ras1, the homologue of the human transformingrasgenes, has been shown to be active in the posterior termini of theDrosophilaembryo and in the eye imaginal disc in pathways of cell fate determination. We demonstrate that during embryogenesisRas1transcripts are restricted mainly to the embryonic central nervous system, suggesting that the gene product also may have a role in these nerve cells.Rlb1encodes for a novel, lysine‐rich basic protein. It is expressed mainly in the developing midgut and in the somatic mesoderm.Rlc1also encodes for a novel, basic protein. The expression ofRlc1during embryogenesis is similar, but not identical, to the expression pattern detected forRas1. The vertebrate p21Rasproteins are bound to the inner face of the cell membrane. Ras1, theDrosophilahomologue of p21, and the Rlb1 protein, are also non‐cytoplasmic, membranous proteins. Rlb1 is found in the cell membrane of larval midgut epithelial cells. In addition, Rlb1 is detected in the nuclei of these cells, and in the nuclei of the midgut imaginal cells. © 1994 Wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1002010208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe developmental relations between abducens (VI) nerves and their targets, the lateral rectus, quadratus, and pyramidalis muscles, have been examined in the chick embryo from early neural tube stages through 10 days of incubation. Sites of myoblast origins were determined by microinjection of replication‐incompetent retroviruses containing theLacZreporter into paraxial mesoderm corresponding to somitomeres 3‐5. Motor neurons and axons were identified by Bodian staining, immunocytochemistry, and application of DiI and DiO to dissected peripheral nerves. Anlage of the dorsal oblique originate in somitomere 3, close to the ventrolateral margin of the mid‐to‐caudal mesencephalon. Precursors of the lateral rectus arise deep within somitomere 4, beside the future metencephalon (rhombomere “A”). Quadratus and pyramidalis precursors are located between and partially segregated from these other two anlage. VIth nerve axons exit rhombomeres 5 and 6 via multiple median roots, fasciculate, and by stage 17 have elongated rostrally beneath the hindbrain. Immediately caudal to a mesenchymal pre‐muscle condensation located deep to rhombomere 2, the VIth nerve separates into two branches. One branch enters the rostral portion of the condensation, from which quadratus and pyramidalis muscles will segregate. This branch projects exclusively from rhombomere 5 and is the accessory abducens nerve. The other branch enters the caudal, presumptive lateral rectus, region of the condensation. This is the abducens nerve, and it projects from cells located in both rhombomeres 5 and 6. These findings indicate that specific matching of motor nerves with their presumptive targets begins prior to the differentiation and segregation of myogenic populations, and that spatial organization of developing eye muscles is initiated well before they interact with connective tissue precursors derived from the neural crest. © 1994 W

ISSN:1058-8388    

DOI:10.1002/aja.1002010209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:1058-8388    

DOI:10.1002/aja.1002010201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY