Oxygen Sensing In Tissues

This book covers a wide biological range of problems regarding oxygen sensing in tissues. Oxygen sensing is defined as a process in which 02 reacts with different cellular components to avoid hypoxic cell damages. Oxygen sensing contributes to auxiliary mechanisms which help bacteria, invertebrates, vertebrates, and mammalians to survive and withstand hypoxic sensations. For the first time, experts from different disciplines have cooperated in examining various biological systems exhibiting this phenomenon.

Proceedings of the XIVth International Symposium on Arterial Chemoreception, held June 24-28, 1999, in Philadelphia, Pennsylvania. This volume, containing the proceedings of the fourteenth biannual ISAC meeting presents a new departure from their traditional focus on arterial chemoreceptors and their functions, in the expansion to include the study and discussion of oxygen sensing in other tissues and cells, and the genes involved. Bringing together scientists from cellular and systemic boundaries of physiology, working at the interface of cellular and molecular biology, this book, containing new physiological and biochemical perspectives.

This monograph contains the proceedings of a symposium entitled, "Tissue Hypoxia and Ischemia," which was held at the Annenberg Center of the University of Pennsylvania on August 13 and 14, 1976. The symposium was jointly sponsored by the following groups at the University of Pennsylvania: the Respiratory Physiology Group of the Department of Physio logy, the Cardiopulmonary Section of the Department of Medicine, the Johnson Research Foundation, the Cerebrovascular Research Center of the Department of Neurology, the Head Injury Center of the Department of Neurosurgery, the. Institute for Environ mental Medicine, and the International Society on Oxygen Transport to Tissues. Its purpose was to promote an interdisciplinary discussion of oxygen sensors in various tissues and their mechanism of action as well as to examine the deleterious effects of hypoxia and ischemia with special reference to the brain. There were four sessions, one on the biochemistry of physi ologic oxygen sensors, two on the mechanism of oxygen sensing in tissues and one on the circulatory and metabolic aspects of cerebral hypoxia and ischemia.

This presentation describes various aspects of the regulation of tissue oxygenation, including the roles of the circulatory system, respiratory system, and blood, the carrier of oxygen within these components of the cardiorespiratory system. The respiratory system takes oxygen from the atmosphere and transports it by diffusion from the air in the alveoli to the blood flowing through the pulmonary capillaries. The cardiovascular system then moves the oxygenated blood from the heart to the microcirculation of the various organs by convection, where oxygen is released from hemoglobin in the red blood cells and moves to the parenchymal cells of each tissue by diffusion. Oxygen that has diffused into cells is then utilized in the mitochondria to produce adenosine triphosphate (ATP), the energy currency of all cells. The mitochondria are able to produce ATP until the oxygen tension or PO2 on the cell surface falls to a critical level of about 4–5 mm Hg. Thus, in order to meet the energetic needs of cells, it is important to maintain a continuous supply of oxygen to the mitochondria at or above the critical PO2 . In order to accomplish this desired outcome, the cardiorespiratory system, including the blood, must be capable of regulation to ensure survival of all tissues under a wide range of circumstances. The purpose of this presentation is to provide basic information about the operation and regulation of the cardiovascular and respiratory systems, as well as the properties of the blood and parenchymal cells, so that a fundamental understanding of the regulation of tissue oxygenation is achieved.

This book describes the methods of analysis and determination of oxidants and oxidative stress in biological systems. Reviews and protocols on select methods of analysis of ROS, RNS, oxygen, redox status, and oxidative stress in biological systems are described in detail. It is an essential resource for both novices and experts in the field of oxidant and oxidative stress biology.

Oxygen sensing is a key physiological function of many tissues, but the identity of the sensor, the signalling pathways linking the sensor to the effector, and the endpoint effector mechanisms are all subjects of controversy. This book evaluates the various mediators that have been proposed, including the mitochondria, NAD(P)H oxidases, cytochrome p450 enzymes, and direct effects on enzymes and ion channels. There has been a resurgence of interest in the role of mitochondria, based partly on the ability of mitochondrial inhibitors to mimic hypoxia, but there is little consensus concerning mechanisms. Some favour the view that the primary signalling event is a reduction in cell redox state and reactive oxygen species (ROS) due to general inhibition of the electron transport chain (ETC); others support a key role for complex III of the ETC and an increase in ROS generation, while others doubt either of these components is the key intermediary. All these hypotheses are discussed in the book, together with conceptual problems concerning the ability of mitochondria to respond to physiological hypoxia. The other area of controversy covered in the book is the identity of the endpoint effector(s). Some authors favour K+ channel inhibition, followed by depolarization and Ca2+ entry via L-type channels, while others propose that release of Ca2+ from intracellular stores, or capacitative Ca2+ entry and other voltage-independent pathways may be more important. The book also describes evidence for an endothelium-dependent Ca2+-sensitizing pathway involving Rho and possibly other kinases. While some of these differences can be attributed to variation between tissues, many must be related to differences in interpretation or methodology. In this book, experts in the field of acute oxygen sensing working in different tissues address these controversies and their possible origins, and discuss possible approaches whereby these controversies might be resolved. The book will be of great interest to all those working in fields where oxygen sensing is important, particularly cancer and wound healing, as well as researchers in drug discovery and biotechnology.

The ability of cells to sense and respond to changes in oxygenation underlies a multitude of developmental, physiological, and pathological processes. This volume provides a comprehensive compendium of experimental approaches to the study of oxygen sensing in 48 chapters that are written by leaders in their fields.

This volume contains the papers which were presented at the Third International Symposium on Oxygen Transport to Tissue together with the discussions at the end of each Session. The meeting was held at Churchill College, Cambridge from July 4th-7th 1977. Our special thanks are due to Mrs. Valerie Jeal and Mr. Charles Drown of the Department of Pathology, Bristol, who were invaluable in ensuring the smooth running of the meeting and the preparation of this book. We are very grateful to Dr. Marian Silver for proof-reading and helping to disentangle the "discussion". We would also express our thanks for the general help received from Janet and Fiona Silver and Steven James and our appreciation of the cheerful assistance of Miss Sadie Williams in putting the finishing touches to the manuscript. August, 1977 I. A. Silver M. Erecinska H. I. Bicher Contents Session 1 - OXYGEN ELECTRODES AND BLOOD MONITORING DEVICES The Bitumen P0 Electrode - A New Method to 2 Manufacture P0 Needle Electrodes 3 2 H. Acker, D. Sylvester, E. Dufau, and H. Durst A Working Equation for Oxygen Sensing Disk Electrodes • • • • • • 9 T. E. Tang, R. E. Barr, V. G. Murphy, and A. W. Hahn Variations on the Response Characteristics of Oxygen Electrodes •••• 17 R. E. Barr, T. E. Tang, and A. W. Hahn Directly Heated Transcutaneous Oxygen Sensor 25 H. P. Kimmich, J. G. Spaan, and F.