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Biomedical subjects

N Holder

Publications and source records attributed to N Holder.

79 records · Page 5Linked to original sources
PubMed1979

Interactions between irradiated and unirradiated tissues during supernumerary limb formation in the newt.

The interactions between irradiated and unirradiated blastemas and stumps in the newt forelimb were studied. Irradiated right blastemas at the stage of early digits were grafted to unirradiated left stumps and unirradiated left blastemas were grafted to irradiated right stumps. Grafts were oriented with their anterior-posterior axes opposed to that of the stumps. Supernumerary limbs ranging in completeness from one to four digits were found to arise predominantly on the anterior or posterior sides of the host limb. The graft developed well when the blastema was unirradiated and had reversed handedness with respect to the stump. Irradiated grafts developed poorly. On occasions, limbs with two supernumerary structures were found. The results are discussed in terms of the origin of the cells which comprise the supernumerary limbs and their bearing on a recently presented model concerned with pattern specification and regulation in epimorphic fields.

Animals↗
PubMed1978

The onset of osteogenesis in the developing chick limb.

The pattern of the onset of osteogenesis in each of the skeletal elements of the developing limbs of the chick embryo is described using Alizarin-red-stained whole mounts. Grafting experiments where 6-day unossified cartilage rudiments are placed into 4-day host wings show the initiation of ossification to be a programmed event. Truncation experiments show this to be the case not only for the initial onset of osteogenesis, but also for each region of each element. These results are discussed in terms of morphogenetic events occurring in the early wing bud.

Animals↗
PubMed1977

An experimental investigation into the early development of the chick elbow joint.

The theory that differential growth of opposed chondrogenic centres is important in early joint formation has been tested experimentally by removing structures in relation to the chick elbow joint. The humerus and its cap of differentiating joint cells were found to develop independently of structures distal to them. Removal of the presumptive joint region at early stages resulted in fusion of the humerus with the radius and ulna. Results are discussed in terms of concepts concerning pattern formation of cell types in the early wing-bud.

Animals↗