The Symposium on Brain Edema has been organized by the Osterreichische Arbeitsgemeinschaft fur Neuropathologie and by the Problem Commission for Neuropathology of the World Federa tion of Neurology. We would like to express our thanks to Dr. L. van Bogaert, president of the W.F.N., for his great interest in the design of this conference and for his energetic support. One of the aims ofthe Problem Commission for Neuropathology has been to contribute to the advances in various problems which are becoming ripe for elucidation by experts in different fields. The idea of the Symposium on Brain Edema has as its background a compelling necessity to elucidate this subject which is clinically so important and neuropathologic ally so poorly understood. It was hoped that this could be achieved by a multidisciplinary approach involving a variety of aspects to be discussed and correlated. Brain edema, being an abnormal cerebral condition, belongs basically to the sphere of neuropathology, but to be successful in our endeavors we had to apply neuropathology in its most modern and widest terms. By this we understand that such neuropathology includes the study of all abnormal phenomena in the nervous tissue related to the structural alterations, and by "structural" we mean not only tissual or cellular ones but also changes on ultrastructural and molecular levels. Thus we needed close and integrated coopera tion of experts in fields such as neurohistology, histochemistry, electron microscopy, neurochemistry, and neurophysiology.

The first International Symposium on Brain Edema was organized by Dr. Klatzo and Dr. Seitelberger and held in Vienna in 1965. The second Symposium was held in Mainz in 1972 and organized by Dr. H. J. Reulen and Dr. K. Schiirmann, the third in Montreal in 1976 by Dr. H. M. Pap- pius, the fourth in Berlin in 1979 by Dr. J. Cervos-Navarro, and the fifth in Groningen in 1982 by Dr. K. G. Go. This volume contains the papers presented at the 6th International Sym- posium on Brain Edema, held in Tokyo, Japan, November 7-10, 1984. The invited lectures by Dr. I. Klatzo, Dr. A. Hirano, Dr. S. I. Rapoport, Dr. B. K. Siesj6, Dr. H. M. Pappi us, Dr. K. A. Hossmann, and Dr. D. M. Long are included as special chapters. On behalf of the organizing committee, I wish to express my deep ap- preciation to all the participants for their contribution toward making this meeting so fruitful and significant. Moreover, the great success of this Sym- posium depended on the high quality of the invited lectures and presen- tations by experts in various fields, as well as on the free and enthusiastic discussion. I was deeply impressed with the papers presented by all the authors, who endeavored to elucidate their subjects. The editors have made only minor corrections and rearrangements, since prompt publi- cation was considered to be important.

The Maturation Phenomenon, described by Ito et al. in 1975 [3) on the basis of his to logical observations in the hippocampus as well as other portions of the cerebral hemisphere, refers to the hours or days of delay in the development of pathological changes in various parameters of ischemic injury following the restoration of blood flow to the ischemic brain. There is a direct relationship between the intensity of ischemic insult and the speed and rate of maturation of ischemic injury, a lesser intensity being associated with slower and less severe development of the lesions. The delayed neuronal death of CAl pyramidal cells of the hippocampus [8) is a classic example. In the cerebral cortex, with increasing intensity of the ischemic insult, the maturation phenomenon of ischemic injuries intensifies, seamlessly, from less exten sive to more extensive disseminated selective neuronal necrosis (DSNN), and then further to cerebral infarction upon reaching a critical threshold [1,2,4,6,7). We also have found that following ischemic insults just under the threshold level required to induce infarction, only disseminated selective neuronal necrosis (DSNN) progresses, while following ischemic insults at the threshold level, initially only DSNN develops, followed by the evolution of a gradually enlarging infarcted focus [5, 7). The reporting of this phenomenon boosted research in the field, as it became evi dent that ischemic damage is not a sudden event, but a process potentially susceptible to therapeutic intervention.

Many nerve cells of the brain which are not killed outright may suffer delayed death or recovery after ischemic insult. This fact has led to the concept of "maturation phenomenon" of neuronal injuries. Since the 1st International Symposium on Maturation Phenomenon in 1990, new developments, particularly in molecular biology, have been rapidly bringing new information about molecular nature and mechanisms of cell death. This book contains the presentations of the 2nd International Symposium held in Tokyo in April 1996. The latest developments in maturation phenomenon and the present status of investigation are described and further stimulation of research in this field is provided.

The topic "Cerebrovascular Transport Mechanisms" was chosen by the General Couneil of the International Society of Neuropathology as one of the four main symposia at the IX International Congress of Neuropathology, September 1982 in Vienna. The chairmen of the symposium were asked to structure a program which would cover the reeent devel- opments in this field and which could serve as a background for free communications, relevant to this topic, submitted by the participants of the Congress. Cerebrovascular transport mechanisms refleet the main function of the blood-brain barrier in providing optimaI, homeostatically regulated, biochemical environment for the brain. It is obvious that disturbanees of this function may play a significant role in patho- physiology of various brain disorders. Since the elucidation of the complex blood-brain barrier phenomenon, consisting of various "barrier systems", necessarily requires applica- tion of multidisciplinary approaches, the program of this symposium was structured by evaluation of ultrastructural, cytochemical, physiological, biochemical, pathophysiological and therapeutic aspects of the blood-brain barrier by invited, recognized experts in respec- tive areas. As aresult, this volume of the proceedings of the symposium attempts to summarize much of today's knowledge on cerebrovascular transport mechanisms in health and disease, and is supplemented by the abstracts of free communications dealing with the most reeent research in this field. We hope that this volume wil1 serve both as an introduction and a reference book, and that it wil1 stimulate further research.