摘要:

AbstractThe differentiation of neural crest cells into catecholaminergic neurons is dependent upon both intrinsic properties and signals from the embryonic microenvironment. In tissue culture, the development of catecholaminergic traits is dependent upon factors present in chick embryo extract (CEE). This dependency suggests that soluble growth factors affect catecholaminergic differentiationin vivo. We have studied the role of CEE‐derived factors and the potentially related influence of characterized growth factors on catecholaminergic phenotypic expression in avian neural crest cells. In this report, we show that CEE‐derived factors and transforming growth factor beta1(TGF‐β1) differentially influence catecholaminergic phenotypic expression as well as melanogenesis. TGF‐β1substituted for CEE‐derived factors and supported the in vitro differentiation of tyrosine hydroxylase (TH) and dopamine‐β‐hydroxylase (DBH) immunoreactivities, as well as catecholamine biosynthesis and storage. Differentiation of catecholaminergic cells was dependent on factors present in 10% CEE during the first 1–4 days in culture suggesting an initial critical period for exposure. One day of initial exposure to either CEE‐derived factors or TGF‐β1was sufficient to support the subsequent expression of catecholaminergic phenotypic characteristics. The time course of responsiveness to TGF‐β1was different than for CEE‐derived factors. Neural crest cells remain responsive to TGF‐β1for at least 5 days, which is past the critical period for CEE‐derived factors. Bioassay of CEE shows that endogenous levels of TGF‐β are less than or equal to 0.5 ng/ml. Immunoprecipitation of TGF‐β from CEE or blockade by neutralizing antibodies did not result in a loss of catecholaminergic differentiation by neural crest cells. Although CEE supports melanogenesis under all of the growth conditions tested, TGF‐β1was foun

ISSN:1058-8388    

DOI:10.1002/aja.1001960102

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe report on theXenopushomolog of theHox 2.4gene. This gene occupies the next to 5′‐most position in theXenopus Hox2 complex.Hox 2.4RNA is first detected at the early neurula stage, reaching a peak at the early tailbud stage, and is localized in the middle and posterior portions of the embryos Antibodies raised against a fusion protein show expression ofHox 2.4protein inXenopusembryos in a band located in the mid spinal cord. Thus, the protein is expressed in a narrower domain than that ofHox 2.4mRNA. TheXenopus Hox 2.4antibody cross‐reacts readily with mouse embryonic tissue, where the protein is detected in migrating neural crest cells, the dorsal portion of the spinal cord, somites, lateral plate mesoderm, and in the forelimb bud. TheXenopus Hox 2.4intron shares considerable sequence identity with the intron in the mouse homolog. A reporter gene containing an element from this intron which can bind homeodomain proteins is activated following microinjection intoXenopusembryos. The short distance between the end of theHox 2.4cDNA and the start site of the neighboring gene in the complex raises the possibility that this transcriptional element might be shared by twoHoxgenes. © 1993 wiley‐L

ISSN:1058-8388    

DOI:10.1002/aja.1001960103

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe functional diversity of skeletal muscle is largely determined by the combinations of contractile protein isoforms that are expressed in different fibers. Just how the developmental expression of this large array of genes is regulated to give functional phenotypes is thus of great interest. In the present study, we perform a comprehensive analysis of contractile protein isoform mRNA profiles in skeletal muscle systems representing each generation of fiber formed: primary, secondary, and regenerating fibers. We find that in each system examined there is a common pattern of isoform gene expression during early differentiation for 5 of the 6 gene families we have investigated: myosin light chain (MLC)1, MLC2, tropomyosin, troponin (Tn)C, and TnI. We suggest that the common isoform patterns observed together represent a genetic program of skeletal muscle differentiation that is independent of the mature fiber phenotype and is found in all newly formed myotubes. Within each of these contractile protein gene families the program is independent of the isoforms of myosin heavy chain (MHC) expressed. The maintenance of such a program may reflect a specific requirement of the initial differentiation process. © 1993 wiley‐Liss, I

ISSN:1058-8388    

DOI:10.1002/aja.1001960104

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

年代:1993

数据来源: WILEY

摘要:

AbstractPolyclonal antibodies were raised in rabbits against a fusion peptide representing a portion of the amino‐terminal non‐triplehelical domain of mouse type XII collagen. The antibodies reacted with bands of 220 and 350 kDa on Western blots of mouse tissue extracts. Immunohistochemical analyses of mouse embryos demonstrated that type XII collagen is expressed mainly in dense connective tissues of tendons, ligaments, dermis, cornea, blood vessel walls, meninges, and developing membranous bones. Comparison of skin extracts and medium of cultured mouse skin fibroblasts by Western blotting showed that while tissues contain short 220 kDa type XII collagen polypeptides as well as the long form, cultured cells produce mainly the long form with 350 kDa polypeptides. © 1993 wiley‐Lis

ISSN:1058-8388    

DOI:10.1002/aja.1001960105

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe have examined the pattern of immunoreactivity of a monoclonal antibody, II‐5B2, with specificity for an epitope which resides within the NH2‐terminal extension peptide (telopeptide) of the avian type II collagen molecule. This epitope is available in regions of matrix where de novo synthesis of the molecule is ongoing, but not where synthesis has ceased and maturation and crosslink formation have occurred. Within the cartilaginous growth plate, the epitope disappears from the matrix soon after the chondrocytes become hypertrophic; within the cornea, the epitope disappears subjacent to the epithelium. The II‐5B2 epitope is not made available by a variety of procedures shown to remove potentially masking substances and to disrupt fibrillar organization. It is rendered available, however, when covalent crosslink formation between collagen molecules is blocked through administration of β‐aminopropionitrile or penicillamine. In contrast, the epitope of another monoclonal antibody against type II collagen, II‐II6B3, which resides in the triple‐helical domain of the molecule, in cartilage is present throughout the growth plate including the hypertrophic zone, and in cornea extends for a considerable distance into the stroma. Thus, it is available for antibody binding regardless of fibril maturation and crosslinking. These data suggest that the II‐5B2 epitope becomes unavailable when the telopeptide becomes cross‐linked. By using these two monoclonal antibodies in serial sections, one can establish the crosslinking pattern of type II collagen in the tissue. This set of antibodies is a potentially useful tool for analyzing normal and abnormal development, remodeling, and repair processes in the skeletal system and in other tissues where type II collagen is involved in organization of the matrix, such as the primary corneal stroma. © 199

ISSN:1058-8388    

DOI:10.1002/aja.1001960106

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn the cartilaginous epiphyseal growth plate, extracellular matrix molecules such as collagens are believed to play important roles during both normal and abnormal development. One defect of the epiphyseal plate occurs in chickens with a condition termed tibial dyschondroplasia (TD). This abnormality occurs in certain strains of juvenile chickens and other rapidly developing animals. It is characterized by the presence of a mass of avascular, uncalcified cartilage which is retained in the proximal metaphysis of the tibiotarsus. To elucidate the developmental events which may be involved in this lesion, we have performed both immunohistochemistry and in situ hybridizations for collagen types II and X, known components of the extracellular matrix of the growth plate. By immunohistochemical analyses, the TD lesion contains both of these collagen types; therefore, the presence of these molecules per se is not sufficient for calcification of vascularization to occur. Since type X collagen is expressed exclusively in hypertrophic cartilage, the chondrocytes in the lesion must have undergone hypertrophy before their developmental arrest. The matrix of the lesion also reacted with a monoclonal antibody which is directed against an epitope in the NH2‐terminal telopeptide of the α1(II) chain. Our previous data suggest that this epitope is rendered unavailable in type II collagen which has undergone crosslink formation; its availability in the lesion suggests that crosslinking may be abnormal. Lastly, analyses by in situ hybridization failed to detect mRNA for either type II or type X collagen within the lesion, but chondrocytes distal to the lesion do contain mRNAs for these collagens in a spatial pattern suggesting the presence of a second growth plate. © 1993 wiley‐Liss

ISSN:1058-8388    

DOI:10.1002/aja.1001960107

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe myocardial and endocardial cell sorting out processes take place primarily between 19 and 29 hr of development in the avian embryo. This occurs in an apparent rostral to caudal wave through the heart forming region. During heart development considerable uncertainty exists regarding the processes that regulate cell commitments, progressive aggregation, and sorting out of the different precardiac cell populations. The question addressed in this report is whether endocardial and myocardial cells have a common origin or do the endocardial cells arise from a distinct population of cells from within the precardiac mesoderm. These cells then migrate to become localized between the developing myocardium above and the endoderm below. The distribution of preendocardial cells and premyocardial cells has been followed immunohistochemically in quail heart‐forming region mesoderm explants from embryos approximately 18 hr in development and incubated for a 24‐hr period. Differentiating myocardiocytes were immunostained with anti‐N‐cadherin and endocardiocytes with QH‐1, a monoclonal antibody that recognizes an antigenic determinant on quail endothelial cells. Sparsely localized QH‐1 labeled endothelial cells are localized in the stage 5 heart‐forming region. These cells are often arranged in a columnar fashion in the mesoderm explants 6 hr after explantation. By 15–22 hr large patches of QH‐1 expressing cells are interspersed with the N‐cadherin expressing myocardiocytes. A subpopulation of cells expressbothN‐cadherin and QH‐1 antigen suggesting that endocardial and myocardial cells may arise from a common precursor population and that N‐cadherin regulation may be a mechanism underlying specific cell sorting of these two cell populations during heart developmen

ISSN:1058-8388    

DOI:10.1002/aja.1001960108

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

年代:1993

数据来源: WILEY

摘要:

AbstractChicken embryos were immunolabeled with antibodies to fibrillin, an extracelular matrix molecule implicated in the Marfan syndrome. The pattern of labeling, established using both whole‐mounted and sectioned embryos, showed a striking localization at the primary axis of the early embryo, including Hensen's node. After stage 8, the labeling of Hensen's node diminished while other structures in the embryo exhibited increased immunolabeling. These structures include the region of the presumptive dorsal aorta, the ventral surface of the notochord, and the mesocardium. Injections of the antibody between the vitelline membrane and the blastoderm in vivo failed to perturb the development of embryos, thus precluding any conclusions regarding the function of fibrillin. © 1993 wiley‐Liss,

ISSN:1058-8388    

DOI:10.1002/aja.1001960109

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

年代:1993

数据来源: WILEY

ISSN:1058-8388    

DOI:10.1002/aja.1001960101

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

年代:1993

数据来源: WILEY