INTRODUCTION Embryonic development is controlled by a series of basic regulatory processes, including the regulation of protrusion and outgrowth. It has become clear that such developmental processes require coordinated reciprocal interactions between epithelium and the adjacent mesenchyme, frequently mediated through hedgehog, Wnt and fibroblast growth factor (Fgf) pathways. Perturbation of th...

Rat embryos, dissected from the uterus at 11 1/2 days' gestation, have been used to study the regenerative powers of the embryonic limb. One forelimb-bud of each embryo was amputated, via an incision in the membranes. Embryos were subsequently grown in roller-bottle cultures for 44 h, then examined histologically. Twenty-nine out of 32 healthy embryos had formed limb-bud regenerates, 14 of whic...

We report development of a model of retroviral gene transduction in high-density limb bud cell micromass culture. The replication competent avian retrovirus RCAS BP (A) carrying the human placental alkaline phosphatase gene (RCAS AP) was used as a marker for retroviral infection and spread. The final protocol balances the need to allow time for retroviral integration and gene transduction again...

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 demonstrate that Sprouty genes 1, 2 and 4 are expressed in several developing organs of the craniofacial area and trunk, including the brain, cochlea, nasal organs, teeth, salivary gland, lungs, digestive tract, kidneys and limb buds. In organs such as the semicircular canal, Rathke's pouch, nasal organs, the follicle of vibrissae and teeth, Sprouty1 and Sprouty2 are expressed in the epithel...

In certain urodeles, a lost appendage, including hand and foot, can be completely replaced through epimorphic regeneration. The regeneration process involves cellular activities similar to those described for embryogenesis. Working on the assumption that the morphological pattern specific for a forelimb or a hindlimb is controlled by different gene activities in the two limbs, we employed a mRN...

In avian hypertrophic cartilage, the maturation pathway from mesenchymal prechondrogenic cells to fully differentiated hypertrophic chondrocytes proceeds through differentiation stages that can be defined by biochemical markers and several other parameters such as cell volume, cellular phenotype and growth kinetics. The chondrocyte differentiation process is divided into three schematic cellula...

The vertebrate limb bud arises from lateral plate mesoderm and its overlying ectoderm. Despite progress regarding the genetic requirements for limb development, morphogenetic mechanisms that generate early outgrowth remain relatively undefined. We show by live imaging and lineage tracing in different vertebrate models that the lateral plate contributes mesoderm to the early limb bud through dir...

This study aimed at characterizing the Sonic hedgehog (shh) gene in newt limbs, which encodes a signaling molecule of the zone of polarizing activity (ZPA) responsible for determining the anterior-posterior axis of the embryonic chicken and mouse limbs. The reverse transcription-PCR showed that adult newt regenerating limbs express shh genes. In situ hybridization experiments demonstrated that ...

This study examined the possible developmental relationship between differential amounts of glycosaminoglycans (GAG) within the ectodermal basement membrane and initiation of limb outgrowth. Chick embryos at stages 11-20 were labeled in ovo with 35SO4 and processed for autoradiography. After exposure to sulfate for 15 min. The label was localized within the surface ectoderm whereas after 3 h th...