Cryptic responses to tissue manipulations in avian embryos

摘要: Experimental embryology performed on avian embryos combines tissue manipulations and cell-labeling methods with increasing opportunities demands for critical assays of the results. These approaches continue to reveal unexpected complexities in normal patterns cell movement origins, documentation which is unraveling intricacies interactions during embryogenesis. Viktor Hamburger's many pioneering contributions helped launch promote philosophical as well technical elements experimental embryology. Furthermore, his scholarship profoundly positive presence influenced not just those us fortunate have trained him, but several generations developmental biologists. The first part this article presents examples rewards that occurred due influences. Surgical manipulation embryonic tissues always introduces a greater number variables than experimenter can control or, often, readily identify. We present results dorsal ventral lesions hindbrain segments, include defects structures within, beside, also at considerable distance from site lesion. Extramedullary loops longitudinal tract axons exit re-enter neural tube, intra-medullary proliferation blood vessels expanded. Peripherally, coalescence crest- placode-derived neuroblasts disrupted. As expected, motor neurons their projections close sites lesion are compromised. However, an finding cranial nerves located distant were Following brainstem region rhombomeres 3, 4 or 5, trigeminal oculomotor penetrated lateral rectus muscle. Surprisingly, ability VIth nerve reach muscle was destroyed most cases, even though terrain through they needed pass typically followed more course normal, usually, emerging individual roots failed fasciculate into common nerve, suggests each rootlet contains pathfinder-competent axons. lesson these surgical intervention may substantial effects upon adjacent to, being manipulated.