Bio-Medical Materials and Engineering - Volume 18, issue 4-5
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The aim of
Bio-Medical Materials and Engineering is to promote the welfare of humans and to help them keep healthy. This international journal is an interdisciplinary journal that publishes original research papers, review articles and brief notes on materials and engineering for biological and medical systems.
Articles in this peer-reviewed journal cover a wide range of topics, including, but not limited to: Engineering as applied to improving diagnosis, therapy, and prevention of disease and injury, and better substitutes for damaged or disabled human organs; Studies of biomaterial interactions with the human body, bio-compatibility, interfacial and interaction problems; Biomechanical behavior under biological and/or medical conditions; Mechanical and biological properties of membrane biomaterials; Cellular and tissue engineering, physiological, biophysical, biochemical bioengineering aspects; Implant failure fields and degradation of implants. Biomimetics engineering and materials including system analysis as supporter for aged people and as rehabilitation; Bioengineering and materials technology as applied to the decontamination against environmental problems; Biosensors, bioreactors, bioprocess instrumentation and control system; Application to food engineering; Standardization problems on biomaterials and related products; Assessment of reliability and safety of biomedical materials and man-machine systems; and Product liability of biomaterials and related products.
Abstract: Hypoxia is a diminution of oxygen quantity delivered to tissue for cellular need to product energy. Hypoxia derives from two major conditions in health diseases: anemia and ischemia. Anemic hypoxia comes from damage to O2 transport like red blood cells diminution or disease. Ischemic hypoxia is a diminution of blood flow following a diminution of blood volume after a hemorrhagic shock. After hypoxia, vessels dilate to increase blood flow allowing a better oxygenation of peripheral tissues. This vasodilation appears immediately after the beginning of hypoxia and can be maintained during several hours. Today, the molecular mechanisms of this vasodilation…stay unclear. But it seems that potassic channels, ATP concentration and medium acidification in addition to vasodilator/vasoconstrictor balance play a great role to facilitate the oxygenation of the ischemic areas. As endothelial cells (EC) are lining the vasculature, they are always in contact with blood, which carries, amongst other compounds, oxygen. In this way, they are the first target for an oxygen partial pressure (PO2 ) diminution. EC, through different mechanosensors, can sense a variation in PO2 and adapt their metabolism to maintain ATP production. Under hypoxia, EC switch into hypoxic metabolism, leading to the production of reactive oxygen species (ROS). Indeed, when PO2 is low, the respiratory chain in the mitochondria runs slower. Furthermore, cytochrome C capacity to trap O2 is reduced; this phenomenon alters the cellular redox potential and leads to the accumulation of electrons that induce the formation of ROS. This review presents an overview of the behaviour of endothelial cells face to hypoxia. We propose to focus on nitric oxide, hypoxia inducible factor (HIF), lactate and ROS productions. Then we present the different mode of culture of EC under hypoxia. Finally, we conclude on the difficulty to study hypoxia because of the various types of system developed to reproduce this phenomenon and the different signalling ways that can be activated.
Keywords: Endothelial cells, hypoxia, NO, HIF, lactate, ROS
Abstract: Photodynamic therapy (PDT) of skin tumors or pre-cancerous lesions and of age-related macular degeneration combines the administration of porphyrins or porphyrin precursors and illumination with red light at the diseased sites. Photosensitizers absorbing light beyond 630 nm where tissues have the highest transmittance produce singlet oxygen, a highly reactive activated oxygen species and a major cytotoxin. The PDT of age-related macular degeneration is performed with red laser light after i.v. injection of verteporfin (Visudyne® ) a hydrophobic porphyrin carried by serum lipoproteins whose endocytosis leads to accumulation of the porphyrin in endothelial cells of choroidal neo-vessels. In the PDT of…skin cancers, local synthesis of the photosensitizer occurs after topical application of the natural protoporphyrin IX precursor δ-aminolevulinic acid (or its ester forms) on the lesions. In all the cases, the photosensitizers should be rapidly excreted to avoid a long lasting skin photosensitivity.