Neuronal Development

Studies of simple and emerging systems have been undertaken to un derstand the processes by which a developing system unfolds, and to understand more completely the basis of the complexity of the fully formed structures. The nervous system has long been particularly in triguing for such studies, because of the early recognition of a multitude of distinctly differentiated states exhibited by nerve cells with different morphologies. Anatomical studies suggest that one liver cell may be very like another, but indicate that neurons come in a remarkable di versity of forms. This diversity at the anatomical level has parallels at the physiological and biochemical levels. It is becoming increasingly easy to characterize the different cellular phenotypes of neurons. The repeatability with which these phenotypes are expressed may account in part for the specificity and reliability with which neurons form con nections, and it has allowed precise description of the first appearance and further development of the differentiated characteristics of individ ual neurons from relatively undifferentiated precursor cells. This rep resents a major advance over our knowledge of development at the level of tissues, and makes it feasible to define and address questions about the underlying molecular mechanisms involved. Central to these advances has been the clear recognition that there is no single best preparation for the study of neuronal development. Furthermore, it has become evident that no single technique can tell us all we want to know.

Texte du rabat

Studies of simple and emerging systems have been undertaken to un­ derstand the processes by which a developing system unfolds, and to understand more completely the basis of the complexity of the fully formed structures. The nervous system has long been particularly in­ triguing for such studies, because of the early recognition of a multitude of distinctly differentiated states exhibited by nerve cells with different morphologies. Anatomical studies suggest that one liver cell may be very like another, but indicate that neurons come in a remarkable di­ versity of forms. This diversity at the anatomical level has parallels at the physiological and biochemical levels. It is becoming increasingly easy to characterize the different cellular phenotypes of neurons. The repeatability with which these phenotypes are expressed may account in part for the specificity and reliability with which neurons form con­ nections, and it has allowed precise description of the first appearance and further development of the differentiated characteristics of individ­ ual neurons from relatively undifferentiated precursor cells. This rep­ resents a major advance over our knowledge of development at the level of tissues, and makes it feasible to define and address questions about the underlying molecular mechanisms involved. Central to these advances has been the clear recognition that there is no single best preparation for the study of neuronal development. Furthermore, it has become evident that no single technique can tell us all we want to know.

Contenu

1. Cell Lineage in the Development of the Leech Nervous System.- 1. Introduction.- 2. Leech Embryogenesis.- 3. A Novel Cell Lineage Tracing Method.- 4. Development of Germinal Bands.- 5. Origin of the Segmental Ganglia.- 6. Cell-Specific Ablation.- 7. Conclusion.- 8. References.- 2. Origins of the Nervous System in Amphibians.- 1. Introduction.- 2. The Theory of Compartmentation.- 3. Predictions Made from the Theory and Their Experimental Verification.- 4. Critique of the Theory of the Organizer.- 5. Compartment vs. Organizer Theories.- 6. References.- 3. Monoclonal Antibodies to Embryonic Neurons: Cell-Specific Markers for Chick Ciliary Ganglion.- 1. Introduction.- 2. Materials and Methods.- 3. Results.- 4. Discussion.- 5. References.- 4. Genetic Manipulation of Sensory Pathways in Drosophila.- 1. Introduction.- 2. The Experimental Material.- 3. A Theoretical Framework.- 4. Compartments Boundaries and Peripheral Nerves.- 5. Central Projections in Mutants of the Antennapedia Complex.- 6. Central Projections in Mutants of the Bithorax Complex.- 7. Analysis.- 8. References.- 5. Embryonic Development of Identified Neurons in the Grasshopper.- 1. Introduction.- 2. The Grasshopper Nervous System.- 3. Grasshopper Embryology.- 4. Neuronal Precursor Cells.- 5. Early Axonal Pathways.- 6. Cell Lineage of the Median Neuroblast.- 7. Cell Lineage of Midline Precursor 3.- 8. Properties of the Progeny of a Single Precursor.- 9. Morphological Differentiation.- 10. Physiological Differentiation.- 11. Biochemical Differentiation.- 12. Temporal Sequence of Development.- 13. Segment-Specific Cell Death.- 14. Segment-Specific Differentiation.- 15. Limb Bud Removal Experiments.- 16. Conclusions and Questions.- 17. References.- 6. Nerve Fiber Growth and Its Regulation by Extrinsic Factors.- 1. Introduction.- 2. Behavior of the Growing Nerve Fiber Tip.- 3. Structure of the Growing Nerve Fiber.- 4. Mechanism of Nerve Fiber Growth.- 5. Regulation of Nerve Fiber Growth by Environmental Factors.- 6. Regulation of Nerve Fiber Growth by Chemotaxis.- 7. Future Prospects.- 8. Conclusions.- 9. References.- 7. Pioneer Fibers: The Case for Guidance in the Embryonic Nervous System of the Cricket.- 1. Introduction.- 2. First Connections between Periphery and Center: How and When?.- 3. The Events of Sensory Embryogenesis: A Hypothetical Program.- 4. A Matter of Scale.- 5. Periphery and Center.- 6. References.- 8. Mechanisms for the Formation of Synaptic Connections in the Isogenic Nervous System of Daphnia Magna.- 1. Introduction.- 2. The Adult Visual System.- 3. Development of the Visual System.- 4. Experimental Perturbations of Development.- 5. Mechanisms for the Formation of the Eye-Lamina Projection.- 6. References.- 9. Cell Death in Neuronal Development: Regulation by Trophic Factors.- 1. Introduction.- 2. Neuronal Cell Death.- 3. Nerve Growth Factor.- 4. Parasympathetic Neurons.- 5. Other Ganglionic Neurons.- 6. CNS Neurons.- 7. Conclusions.- 8. References.- 10. Neuromuscular Synapse Elimination: Structural, Functional, and Mechanistic Aspects.- 1. Introduction.- 2. General Features of Polyneuronal Innervation and Synapse Elimination.- 3. Mechanisms Underlying Synapse Elimination.- 4. Models and Possible Molecular Mechanisms.- 5. Overview and Conclusion.- 6. References.- 11. Regeneration and Regulation in the Developing Central Nervous System with Special Reference to the Reconstitution of the Optic Tectum of the Chick Following Removal of the Mesencephalic Alar Plate.- 1. Introduction.- 2. Review of Previous Studies of Regeneration in the Developing Central NervousSystem.- 3. Recent Observations on the Regeneration of the Chick Optic Tectum.- 4. References.