Abnormal blood flow in the sublingual microcirculation at high altitude

We report the first direct observations of deranged microcirculatory blood flow at high altitude, using sidestream dark-field imaging. Images of the sublingual microcirculation were obtained from a group of 12 volunteers during a climbing expedition to Cho Oyu (8,201 m) in the Himalayas. Microcirculatory flow index (MFI) was calculated from the moving images of microcirculatory red blood cell flow, and comparison was made between the baseline and high altitude measurements. Peripheral oxygen saturation (SpO2) and Lake Louise scores (LLS) were recorded along with MFI. Our data demonstrate that there was a significant reduction in MFI from baseline to 4,900 m in small (less than 25 μm) and medium (26–50 μm) sized blood vessels (P = 0.025 and P = 0.046, respectively). There was no significant correlation between MFI and SpO2 or MFI and LLS. Disruption of blood flow within microcirculatory may explain persistent abnormal oxygen flux to tissues following the normalisation of systemic oxygen delivery that accompanies acclimatisation to high altitude

Deterministic Chaos and Fractal Complexity in the Dynamics of Cardiovascular Behavior: Perspectives on a New Frontier

Physiological systems such as the cardiovascular system are capable of five kinds of behavior: equilibrium, periodicity, quasi-periodicity, deterministic chaos and random behavior. Systems adopt one or more these behaviors depending on the function they have evolved to perform. The emerging mathematical concepts of fractal mathematics and chaos theory are extending our ability to study physiological behavior. Fractal geometry is observed in the physical structure of pathways, networks and macroscopic structures such the vasculature and the His-Purkinje network of the heart. Fractal structure is also observed in processes in time, such as heart rate variability. Chaos theory describes the underlying dynamics of the system, and chaotic behavior is also observed at many levels, from effector molecules in the cell to heart function and blood pressure. This review discusses the role of fractal structure and chaos in the cardiovascular system at the level of the heart and blood vessels, and at the cellular level. Key functional consequences of these phenomena are highlighted, and a perspective provided on the possible evolutionary origins of chaotic behavior and fractal structure. The discussion is non-mathematical with an emphasis on the key underlying concepts

Two-photon microscopy on vital corotid arteries: imaging the relation between collagen and inflammatory cells in atherosclerotic plaques

We used two-photon laser scanning microscopy (TPLSM) to demonstrate for the first time its potential in studying relational details at the cellular level of atherogenesis in intact, viable mouse carotid arteries. Isolated and mounted arteries of ApoE-/-mice, aged 15 or 21 weeks (7 and 13 weeks on western diet), were imaged after labeling with specific fluorescent markers for cell nuclei, inflammatory cells, collagen, and lipids. Data were compared with C57BL6/J mice fed a chow diet. Control vessels had intact endothelium without adhering blood cells or significant intimal collagen labeling. In ApoE-/-mice already at 15 weeks, inflammatory cells adhered to the endothelium and increased labeling of collagen was observed in tunica intima at both lesion-prone and non-lesion-prone sites, indicating endothelium activation. In plaques, internalized inflammatory cell density increased with age and plaque progression in tunicae adventitia and intima, but not media. In the whole plaque, aging or plaque progression did not alter the direct relationship between inflammatory cells and collagen. However, within the fibrous caps specifically, direct contact between inflammatory cells and collagen increased with age. This study demonstrates the potential of TPLSM in determining detailed information regarding the complex relationship between inflammatory cells and collagen during atherogenesi

Electric discharge plasmas influence attachment of cultured CHO k1 cells

Non-thermal plasmas can be generated by electric discharges in gases. These plasmas are reactive media, capable of superficial treatment of various materials. A novel non-thermal atmospheric plasma source (plasma needle) has been developed and tested. Plasma appears at the end of a metal pin as a submillimetre glow. We investigate the possibility of applying the plasma needle directly to living tissues; the final goal is controlled cell treatment in microsurgery. To resolve plasma effects on cells, we study cultured Chinese hamster ovarian cells (CHO-K1) as a model system. When these are exposed to the plasma, instantaneous detachment of cells from the surface and loss of cell-cell interaction is observed. This occurs in the power range 0.1-0.2 W. Cell viability is assessed using propidium iodide (PI) and cell tracker green (CTG) fluorescent staining utilizing confocal laser scanning microscopy (CLSM). Detached cells remain alive. Use of higher doses (plasma power >0.2 W) results in cell necrosis. In all cases, plasma-influenced cells are strictly localized in submillimetre areas, while no reaction in surrounding cells is observed. Due to its extreme precision, plasma treatment may be applicable in refined tissue modification. Bioelectromagnetics 25:362-368, 2004. © 2004 Wiley-Liss, Inc

Real-time detection of activation patterns in individual platelets during thromboembolism in vivo : differences between thrombus growth and embolus formation

Knowledge on single platelet behavior and intracellular mechanisms during thromboembolism in vivo is scarce. In the present study, we used a new method that enables real-time detection and quantification of activation of individual platelets participating in a thromboembolic process in vivo, using their intracellular free Ca2+ concentration ([Ca2+](i)) as a marker of activation. Isolated platelets were labeled with the Ca2+-sensitive fluorescent probe fluo-3 and injected into anesthetized rabbits so that 0.5-1% of their circulating platelets were labeled. Wall puncture of mesenteric arterioles resulted in thrombus formation followed by embolization. Fluorescence intensity changes of labeled platelets participating in this process were quantified. Within 30 min after injection, labeled platelets behaved similarly to native platelets, and fluorescence intensity was not influenced by dye leakage. Upon adherence to the stationary thrombus, platelets exhibited a prolonged [Ca2+](i) increase, accompanied by shape change and degranulation, which is consistent with a role for strong platelet agonists like collagen. In contrast, when platelets adhered to a growing embolus their [Ca2+](i) rise was transient, and they hardly showed shape change and degranulation, suggesting the involvement of weaker agonists like ADP. These results show, for the first time, the relation between single platelet activation patterns, which are different during thrombus growth and embolus formation, and their behavior in a thromboembolic process in vivo. Copyright (C) 2002 S. Karger AG, Base