Developing Chick Limb Bud Research Articles

The effect of vitamin A on limb regeneration in Rana temporaria

Previous experiments in which vitamin A has been administered to developing or regenerating limbs have shown that different limb axes are affected. In regenerating axolotl limbs, serial reduplications in the proximodistal axis are produced. In the developing chick limb bud, mirror-imaged reduplications in the anteroposterior axis are produced. Results reported here on Rana temporaria limb buds reveal that vitamin A causes both effects to occur. That is, limbs are both serially reduplicated in the proximodistal axis and mirror imaged in the anteroposterior axis. Time and concentration effects are explored and the significance of these results for our current understanding of axial organisation in limbs is discussed.

Pattern Specification and Pattern Regulation in the Embryonic Chick Limb Bud

SYNOPSIS. The embryonic chick limb bud is a growing organ rudiment whose undifferentiated cells give rise to a precise spatial pattern of differentiated structures. The establishment of positional values of chick limb bud cells (pattern specification) and the response of limb bud cells with established positional values to experimental perturbations (pattern regulation) are the major topics considered in this paper. The results of recent experiments with developing chick limb buds analyzing pattern specification and pattern regulation are presented. These studies with the chick limb are described in light of the postulates of a model that was originally formulated from experiments performed on regenerating amphibian and insect appendages.

Evidence for regulation of growth, size and pattern in the developing chick limb bud

ABSTRACT This paper examines the hypothesis that the developing chick limb bud has mechanisms for regulating the control of growth, size and pattern. The tests included: surgical removal of selected parts of the limb field, X-irradiation, temperature shock and the manipulation of known limb organizer regions (removal of the apical ectodermal ridge, or the addition of an extra zone of polarizing activity). The results strongly support the idea that there are regulatory mechanisms controlling both the pattern and the size of the limb and suggest that they involve regulation of the growth rate via control of cell division throughout the embryonic period. Possible mechanisms are discussed.

Identification and distribution of gap junctions in the mesoderm of the developing chick limb bud

Sub-ridge, core, anterior and posterior borders of mesoderm were dissected from stages 22-24 chick wing buds to investigate whether structures for intercellular coupling develop between mesenchymal cells. Fine structure was examined using techniques of transmission electron microscopy, freeze-fracture and scanning electron microscopy. Gap (communicating) junctions which were observed between mesenchymal cells of all limb bud regions were distributed between apposed cell bodies, points of contact between cell processes and other cell bodies, and between contacting tips of slender cell projections. In addition particularly in the the subridge region, filopodia were observed to extend through the intercellular matrix to contact other cells several micrometers distant. The observations reported in this paper show that mesodermal cells throughout the limb have the structural capability for electrotonic and metabolic coupling during a critical period of morphogenesis in the avian limb. Whether intercellular signals which are thought to be transmitted through gap junctions are active in normal limb development remains to be investigated.

The possible differentiation of osteogenic elements in vitro from chick limb mesodermal cells : I. Morphological evidence

In the developing chick limb bud, myogenic, fibrogenic, chondrogenic, and osteogenic tissues are derived from embryonic mesenchyme. Previous reports show that when stage 24 limb mesenchymal cells are cultured in vitro, chondrocytes, fibrocytes, and myocytes can be identified on the basis of morphological and biochemical parameters. The studies reported here clearly demonstrate that, in similar cultures, crystalline calcium phosphate material is deposited in the chondrocytic and fibrocytic matrices. Such crystalline material is not observed before Day 10 of culture life. Subsequent to Day 10 of culture, first amorphous, then crystalline calcium phosphate is observed. On the basis of light and electron microscopic analysis, it appears that the in vitro calcification phenomenon closely resembles the morphological and temporal sequence of osteogenesis observed in vivo.