As traced by Uichael Bradbury in his recently published monograph, The Concept of a BZood-Brain Barrier, the idea of a scientific challenge is just about as old as the twentieth century. Curiously, it remains undefined. Is it a structure or structures as some use the term, or is it a reciprocal per meability, a force-flow relationship, as do others, or is it a group of processes, some more specialized than others? Depend ing upon the observer, the method, and what is observed, it seems to be each of these or all. This Symposium takes as its focus of interest the micro vasculature of the brain and includes considerations of blood flow, the properties of vessel walls and the control of flow and permeability. In addition perturbations that change the characteristics of the flow of materials are given attention. By changing the usual focus of interest, the organizers, Drs. Suddith and Eisenberg, have given a fresh outlook to the subject and now, by publication of the Proceedings, have arranged for wide availability of these interesting papers. Keasley Welch v PREFACE A symposium on the cerebral microvasculature and its function in the blood-brain barrier was held at The University of Texas Medical Branch, Galveston, in the summer of 1979. Investigators from the United States and Europe met to discuss their recent work.

Zusammenfassung
This Symposium takes as its focus of interest the micro vasculature of the brain and includes considerations of blood flow, the properties of vessel walls and the control of flow and permeability.

Inhalt
Section I: Transport Properties and Permeability.- The Basis for Active Transport at the Blood-Brain Barrier.- Studies of Cerebral Capillary Endothelial Membrane.- Biochemical Characteristics of Cerebral Capillaries.- Characteristics of Some Monoamine Uptake Systems in Isolated Cerebral Capillaries.- Transport of Sodium and Potassium across the Blood-Brain Barrier.- Some Properties of Isolated Endothelial Cells in Culture.- Induction of ?-Glutamyl Transpeptidase in Isolated Cerebral Endothelial Cells.- Vascular Basement Membranes: Preparation and Properties of Material Isolated with the Use of Detergents.- The Indicator Extraction Technique. A Method for Studying the Blood-Retinal Barriers.- Central Adrenergic Regulation of Cerebral Microvascular Permeability and Blood Flow; Anatomic and Physiologic Evidence.- Central Adrenergic Regulation of Cerebral Microvascular Permeability and Blood Flow: Pharmacologic Evidence.- Ultrastructural and Histochemical Studies of Cerebral Capillary Synapses.- Cyclic Nucleotide Systems in the Microcirculation of Mammalian Brain.- Section II: Perturbation of the Barrier.- Blood-Brain Barrier Transport During Anesthesia.- Factors which Determine Cerebrovascular Permeability in the Normal Brain and Following Osmotic Treatment.- Endothelial and Astrocytic Cell Membranes in Relation to the Composition of Cerebral Extracellular Fluid.- The Blood-Brain Barrier in Acute and Chronic Hypertension.- Changes in the Cerebral Vasculature after Hypertension and Trauma: A Combined Scanning and Transmission Electron Microscopic Analysis.- Abnormalities of the Cerebral Microcirculation after Traumatic Injury: The Relationship of Hypertension and Prostaglandins.- Freeze Injury and Repair of Cerebral Microvessels.- Alterations in Cerebral Blood Flow Immediately after Brief Periods of Stasis.- The Effect of Severe Hypoxia on Cerebral Glucose Flux.- Behaviour of the Blood-Brain Barrier Toward Biogenic Amines in Experimental Cerebral Ischemia.- Changes in Blood-Brain Transfer Parameters Induced by Hyperosmolar Intracarotid Infusion and by Metastatic Tumor Growth.- Normal and Altered Regional Cerebral Blood Flow and Solute Movement Across the Cerebral Capillary in Rat.