To investigate the role of fibroblast growth factor-2 (basic fibroblast growth factor) in chick limb development, we constructed a replication-defective spleen necrosis virus to ectopically express fibroblast growth factor-2 in stage 20-22 chick limb bud. Because infecting cells in vivo proved to be inefficient, limb bud cells were dissociated, infected in vitro, and then grafted back into host...

T H E limbs of amniote embryos are characterized by a thickening of the epiblast at their tips (Balfour, 1885). Kolliker (1879) illustrated such a thickening in a section of a chick embryo and, according to Braus (1906), was responsible for the term 'ectodermal cap' {Ektodermkappe). Saunders (1948) showed in the chick by experimental means that 'the thickened ectoderm at the apex of the bud' is...

A method of culturing has been employed to compare the properties of cells migrating from small mesodermal explants taken from different regions of normal and mutant limb-buds at different stages of development. An analysis by time-lapse cinematography of the morphology and mobility of cells migrating from explants defines a distal region within the limb-bud where these properties are distinct ...

The regulation of the collagen II gene was investigated by transfecting plasmids containing potential regulatory sequences of this gene coupled to the gene for chloramphenicol acetyltransferase (CAT) into various cells. The 5' flanking region of this gene functioned as a weak promoter when transfected into chicken chondrocytes or fibroblasts. Inclusion of an 800-base fragment from the first int...

In the chick limb bud, the zone of polarizing activity controls limb patterning along the anteroposterior and proximodistal axes. Since retinoic acid can induce ectopic polarizing activity, we examined whether this molecule plays a role in the establishment of the endogenous zone of polarizing activity. Grafts of wing bud mesenchyme treated with physiologic doses of retinoic acid had weak polar...

Bone morphogenetic protein-2 (BMP-2) has been implicated in the polarizing region signalling pathway, which specifies pattern across the antero-posterior of the developing vertebrate limb. Retinoic acid and Sonic Hedgehog (SHH) can act as polarizing signals; when applied anteriorly in the limb bud, they induce mirror-image digit duplications and ectopic Bmp-2 expression in anterior mesenchyme. ...

We show here that bone morphogenetic protein 2 (BMP-2) is involved in patterning the developing chick limb. During early stages of limb development, mesenchymal expression of the Bmp-2 gene is restricted to the posterior part of the bud, in a domain that colocalizes with the polarizing region. The polarizing region is a group of cells at the posterior margin of the limb bud that can respecify t...

Limb bud chondrogenesis in vivo and in vitro appears to depend upon extensive cell contacts leading to localized increases in relative cell density. When cultured in suspension, dissociated early limb bud cells segregate into aggregating and non-aggregating populations. While the non-aggregating cells die, resulting aggregates differentiate exclusively as cartilage. We are investigating the rol...

Background: Cyclosporine A (CsA) is a powerful immunosuppressive agent, which is used for the prevention of allograft rejection and for the treatment of autoimmune diseases.  Many transplant recipients must take this medicine for the rest of their lives.  Females in reproductive age group on prolonged CsA therapy have legitimate concerns about drug effects on pregnancy. Objective: To explore Cs...

Normal patterning of tissues and organs requires the tight restriction of signaling molecules to well-defined organizing centers. In the limb bud, one of the main signaling centers is the zone of polarizing activity (ZPA) that controls growth and patterning through the production of sonic hedgehog (SHH). The appropriate temporal and spatial expression of Shh is crucial for normal limb bud patte...