Search

From time to time, perhaps a few times each century, a revolution occurs that questions some of our basic beliefs and sweeps across otherwise well guarded disciplinary boundaries. These are the periods when science is fun, when new paradigms have to be formulated, and when young scientists can do serious work without first having to acquire all the knowledge of their teachers. The emergence of nonlinear science appears to be one such revolution. In a surprising manner, this new science has disclosed a number of misconceptions in our traditional understanding of determinism. In particular, it has been shown that the notion of predictability, according to which the trajectory of a system can be precisely determined if one knows the equations of motion and the initial conditions, is related to textbook examples of simple; integrable systems. This predictability does not extend to nonlinear, conservative systems in general. Dissipative systems can also show unpredictability, provided that the motion is sustained by externally supplied energy and/or resources. These discoveries, and the associated discovery that even relatively simple nonlinear systems can show extremely complex behavior, have brought about an unprecedented feeling of common interest among scientists from many different disciplines. During the last decade or two we have come to understand that there are universal routes to chaos, we have learned about stretching and folding, and we have discovered the beautiful fractal geometry underlying chaotic attractors.

Proceedings of the NATO Advanced Research Workshop on Molecular Biology and its Application to Medical Mycology, held at Taormina, Italy, January 6-8, 1992

Following pioneering work by Harrison on amphibian limbs in the 1920s and by Saunders (1948) on the apical ridge in chick limbs, limb development became a classical model system for investigating such fundamental developmental issues as tissue interactions and induction, and the control of pattern formation. Earlier international conferences, at Grenoble 1972, Glasgow 1976,and Storrs, Connecticut 1982, reflected the interests and technology of their time. Grenoble was concerned with ectoderm-mesenchyme interaction, but by the time of the Glasgow meeting, the zone of polarizing activity (ZPA) and its role in control of patterning was the dominant theme. Storrs produced the first intimations that the ZPA could be mimicked by retinoic acid (RA), but the diversity of extracellular masrix ~olecules,particularly in skeletogenesis,was the main focus of attention. By 1990, the paradigms had again shifted. Originally, the planners of the ARW saw retinoic acid (as a possible morphogen controlling skeletal patterning), the variety of extracellular matrix components and their roles, and the developmental basis of limb evolution as the leading contemporary topics. However, as planning proceeded, it was clear that the new results emerging from the use of homeobox gene probes (first developed to investigate the genetic control of patterning of Drosophila embryos) to analyse the localised expression of'patterning genes'in limb buds would also be an important theme.

This volume contains the proceedings of the NATO ARW on'Biological Pattern Formation'held at Merton College, University of Oxford, on 27-31 August, 1992. The objective of the workshop was to bring together a select group of theoreticians and experimental biologists to present the latest results in the area of biological pattern formation and to foster interactiqn across dis- plines. The workshop was divided into 5 main areas: (i) limb development, (ii) Dictyostelium discoideum, (iii) Drosophila, (iv) cell movement, (v) g- eral pattern formation. We thank all the participants for their contributions, enthusiasm, and willingness to collaborate. There was a genuine, open, and extremely fru- ful interaction between the experimentalists and theoreticians which made the workshop a success. We also thank The Welcome Trust for providing additional funding. The local organization fell mainly on Denise McKittrick and Beverley Bhaskhare at the Mathematical Institute, Oxford, and Jeanette Hudson and the staff of Merton College. We greatly appreciate their help and patience. We also thank Jonathan Sherratt, Wendy Brandts and Debbie Benson for helping out in the conference and for providing a happy welcome to parti- pants on a typically cold, wet and windy English summer day.

Contributors to this symposium focus on the interface between genes and cells, covering genetic analysis, cloning studies, and the investigation of cell lineages and cellular interactions. They note how the body axes are already determined in the eggs of invertebrates and amphibia, then consider the mechanisms as the egg cleaves, in annelids, arthropods, amphibia, and mice that underlie assignation of cells to specific lineages, which give rise to different tissues in the adult. Closing chapters characterize the molecules that mediate each cell's particular fate, its position in the final body plan as the result of cell sorting or, in some cases, cell migration.

The meetings'At the Frontier of Physics and Biology'are by now regularly organized workshops in Les Houches, France. They provide a truly interdisciplinary forum for physicists and biologists working on similar problems, but using perhaps fundamentally different tools and approaches. The first workshop took place in 1991 under the title'Dynamical Phenomena at Interfaces, Surfaces and Membranes'. This volume contains the material of the second workshop, which brought together geneticists and developmental biologists with physicists, all studying the development of biological form.