Search results for "microcirculation"
showing 10 items of 319 documents
Flow evaluation of red blood cells in capillaroscopic videos
2013
We aim at describing a non-parametric approach to evaluate blood cells velocity in oral capillascopic videos. The proposed methodology is based on the application of standard optical flow algorithms and it is part of a general environment to support during the diagnostic process for evaluating peripheral microcirculation in real time. We validated our approach versus handmade measurements provided by physicians. Results on real data pointed out that our system returns an output coherent to these latter observations.
Effects of Essential Hypertension on coronary Microcirculation: Focus on a Population of Hypertensives Affected by Microvascular Angina
2012
A correlation between essential hypertension and the establishmentof myocardial ischemia is nowadays universally accepted. Coronary atherosclerosis is deemed to be the most important process through which the capability of coronary district to supply a blood flow consistent with myocardial needs can be impaired, until the onset of an anginal syndrome. In this study, we verified whether hypertensives’ coronaries, seen by performing an angiographic study, are properly definable as normal, even in presence of an overt exertional angina, or if they should rather be barely defined as “macroscopically unharmed”, through the clues of a microvascular alteration
Area at Risk and Viability after Myocardial Ischemia and Reperfusion Can Be Determined by Contrast-Enhanced Cardiac Magnetic Resonance Imaging
2008
<i>Background/Aims:</i> Clinical differentiation between infarcted and viable myocardium in the ischemic area at risk is controversial. We investigated the potential of contrast-enhanced cardiac magnetic resonance imaging (ceCMRI) in determining the area at risk 24 h after ischemia. <i>Methods:</i> Myocardial ischemia was induced by percutaneous coronary intervention of the left anterior descending coronary artery in pigs. Coronary occlusion time was 30 min in group A, which caused little myocardial infarction and 45 min in group B, which led to irreversible damage. 24 h after reperfusion ceCMRI was performed at 2 and 15 min after administration of gadolinium-diethyl…
Tumor microenvironmental physiology and its implications for radiation oncology.
2004
Abstract The microenvironmental physiology of tumors is uniquely different from that of normal tissues. It is characterized, inter alia, by O 2 depletion (hypoxia, anoxia), glucose and energy deprivation, high lactate levels, and extracellular acidosis, parameters that are anisotropically distributed within the tumor mass. This hostile microenvironment is largely dictated by the abnormal tumor vasculature and heterogeneous microcirculation. Hypoxia and other hostile microenvironmental parameters are known to directly or indirectly confer resistance to irradiation leading to treatment failure. Hypoxia directly leads to a reduced "fixation" of radiation-induced DNA damage. Indirect mechanisms…
Physiological Mechanisms of Treatment Resistance
2009
It is generally accepted that tumor perfusion, microcirculation, characteristics of the interstitial space of tumors, oxygen (and nutrient) supply, tissue pH distribution and the bioenergetic status—factors that are usually closely linked and that define the so-called pathophysiological microenvironment—can markedly influence the therapeutic response of malignant tumors to sparsely ionizing radiation, chemotherapy, photodynamic therapy, hormonal therapy and immunotherapy. Besides more direct mechanisms involved in the development of acquired therapeutic resistance, there are in addition, obstacles in intratumor pharmacokinetics of antitumor agents due to delivery problems caused by an inade…
Experimentelle und theoretische Untersuchungen der intralienalen Mikrozirkulation beim Kaninchen
1974
1. Bei 57 spontanatmenden Kaninchen wird in Ketaminnarkose mit Hilfe der85Kr(β)-Auswaschtechnik nach Stosinjektion des gelosten Indikators in die Aorta die regionale Milzdurchblutung gemessen. 2. Bei der normalen, unbeeinflusten Milzin situ besteht im Bereich von 65–125 mm Hg eine lineare Abhangigkeit der regionalen Milzdurchblutung vom arteriellen Mitteldruck (2p < 0,001). Bei einem mittleren Druck von 97 mm Hg betragt die mittlere Milzdurchblutung 1,23 ml/g/min. 3. Nach totaler Obstruktion der offenen Strombahn durch Applikation rigider Spharocyten ist die Durchblutung im gleichen Blutdruckbereich unabhangig vom arteriellen Mitteldruck. Nach Ausschaltung der offenen Strombahn betragt die …
Nitric oxide: Relation to integrity, injury, and healing of the gastric mucosa
2001
Nitric oxide (NO) plays a multifaceted role in mucosal integrity. The numerous functions of NO and the double-edged role played by NO in most of them provide a great complexity to the NO action. The three enzymatic sources of NO, neuronal NO-synthase (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS), have been characterised in the gastrointestinal tract. The protective properties of the NO derived from constitutive NO-synthases (eNOS and nNOS) have already been well established. Less clear is the role assigned to iNOS. The simplistic initial view of low levels of NO synthesised by constitutive NOS being protective while exaggerated NO levels after iNOS induction leading irremediably …
Pathophysiological and vascular characteristics of tumours and their importance for hyperthermia: Heterogeneity is the key issue
2010
Tumour blood flow before and during clinically relevant mild hyperthermia exhibits pronounced heterogeneity. Flow changes upon heating are not predictable and are both spatially and temporally highly variable. Flow increases may result in improved heat dissipation to the extent that therapeutically relevant tissue temperatures may not be achieved. This holds especially true for tumours or tumour regions in which flow rates are substantially higher than in the surrounding normal tissues. Changes in tumour oxygenation tend to reflect alterations in blood flow upon hyperthermia. An initial improvement in the oxygenation status, followed by a return to baseline levels (or even a drop to below b…
Circulatory and metabolic responses of malignant tumors during localized hyperthermia
1980
The effect of localized hyperthermia on the circulatory responses and on the oxygen and glucose supply has been evaluated in tissue-isolated rat tumors utilizing an in situ perfusion system. On the average, localized hyperthermia caused a significant increase in total tumor blood flow after raising of the mean tumor temperature from 37 degrees C to 39.5 degrees C. At higher temperatures (42 degrees C) total tumor blood flow decreased to a level somewhat below the flow during normothermia. However, there were great interindividual differences in the response of blood flow to temperature. The changes in blood flow were paralleled by variations of the O2-consumption and of the glucose uptake o…
Experimental evidence for a hyperthermia-induced breakdown of tumor blood flow during normoglycemia
1983
A compilation of experimental data is presented indicating that hyperthermia alone can achieve a significant inhibition of tumor blood flow if appropriate heat exposure times and tissue hyperthermia levels are chosen.