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This Spotlight reviews non-invasive optical methods to determine the blood flow velocity in microcirculation, with an emphasis on the most recent developments, that may be routinely applied in cellular biology laboratories. The methods covered in this book include both scanning and whole-field optical imaging techniques based on endogenous or exogenous (fluorescent) contrast agents for plasma and red-blood-cell visualization, such as laser Doppler velocimetry, laser speckle contrast imaging, diffuse correlation spectroscopy, particle image velocimetry, and two-photon microscopy. Several methods have been developed to quantify the blood flow velocity within microvessels by exploiting the cross-correlation concept applied to optical scanning microscopes: dual-foci cross-correlation, spatio-temporal image correlation spectroscopy, line-scanning techniques, and a recently developed single raster-scanned xy-image technique (FLICS). The basic operational principles, the advantages and disadvantages, and the technical issues of these methods will be discussed and compared, and their applications in biomedical research will be presented.

The endothelium, a monolayer of endothelial cells, constitutes the inner cellular lining of the blood vessels (arteries, veins and capillaries) and the lymphatic system, and therefore is in direct contact with the blood/lymph and the circulating cells. The endothelium is a major player in the control of blood fluidity, platelet aggregation and vascular tone, a major actor in the regulation of immunology, inflammation and angiogenesis, and an important metabolizing and an endocrine organ. Endothelial cells controls vascular tone, and thereby blood flow, by synthesizing and releasing relaxing and contracting factors such as nitric oxide, metabolites of arachidonic acid via the cyclooxygenases, lipoxygenases and cytochrome P450 pathways, various peptides (endothelin, urotensin, CNP, adrenomedullin, etc.), adenosine, purines, reactive oxygen species and so on. Additionally, endothelial ectoenzymes are required steps in the generation of vasoactive hormones such as angiotensin II. An endothelial dysfunction linked to an imbalance in the synthesis and/or the release of these various endothelial factors may explain the initiation of cardiovascular pathologies (from hypertension to atherosclerosis) or their development and perpetuation. Table of Contents: Introduction / Multiple Functions of the Endothelial Cells / Calcium Signaling in Vascular Cells and Cell-to-Cell Communications / Endothelium-Dependent Regulation of Vascular Tone / Conclusion / References

Adequate blood supply to the eye is an important prerequisite for normal visual function. Over the past 40 years our knowledge of ocular blood flow regulation has improved significantly. This reader-friendly textbook provides a comprehensive overview of the current knowledge of ocular blood flow. Lavishly illustrated, it evaluates the wide array of methods that have been used to measure ocular blood flow. Furthermore, it not only offers the reader an evidence-based summary of the physiological and pharmacological properties of ocular blood flow regulation, but also demonstrates the ocular blood flow abnormalities in different vascular diseases. This book will enhance the understanding of all who are interested in learning more about ocular blood flow in health and disease.