Search results for "Circulation"
showing 10 items of 1137 documents
Total (fumarolic + diffuse soil) CO2 output from Furnas volcano
2015
Furnas volcano, in São Miguel island (Azores), being the surface expression of rising hydrothermal steam, is the site of intense carbon dioxide (CO2) release by diffuse degassing and fumaroles. While the diffusive CO2 output has long (since the early 1990s) been characterized by soil CO2 surveys, no information is presently available on the fumarolic CO2 output. Here, we performed (in August 2014) a study in which soil CO2 degassing survey was combined for the first time with the measurement of the fumarolic CO2 flux. The results were achieved by using a GasFinder 2.0 tunable diode laser. Our measurements were performed in two degassing sites at Furnas volcano (Furnas Lake and Furnas Villag…
Rapid Access to Polyfunctional Lipids with Complex Architecture via Oxyanionic Ring-Opening Polymerization
2011
Polymer-coated liposomes, particularly poly(ethylene glycol) (PEG)-substituted liposomes, have emerged as long-circulating carrier systems for drug delivery and diagnostic purposes. A rapid synthesis of three different types of multifunctional lipids with structurally diverse hydrophilic, polyether-based architectures via one- or two-pot approaches is described. Architectural variation is achieved by the combination of different oxyanionic polymerization strategies and various glycidyl ether building units. Branched polyglycerol lipids have been prepared via cholesterol- or 1,2-bis-n-alkyl glyceryl ether-initiated, oxyanionic ring-opening polymerization (ROP) of protected glycidyl ethers an…
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.
Tumour-growth inhibition by induced hyperglycaemia/hyperlactacidaemia and localized hyperthermia.
1996
The present study was undertaken to exploit pathophysiological properties of solid tumours for a tumour-specific therapy. Experiments were carried out on DS-sarcomas implanted s.c. in the hind foot dorsum of Sprague Dawley rats. Treatment strategies included tumour acidification, lactate accumulation and disturbance of the microcirculation by induced systemic hyperglycaemia/hyperlact-acidaemia (15-25/10 mmol/L; for 60 min) as well as localized hyperthermia (water-bath; 43 degrees C, 30 min.). A special infusion solution was developed for the systemic treatment containing glucose, lactic acid and organic buffer without inorganic ions. Growth kinetics of tumour volume and animal survival were…
Response of tumour red blood cell flux to hyperthermia and/or hyperglycaemia.
1989
Laser Doppler flowmetry has been applied to subepidermal rat tumours during localized ultrasound hyperthermia and/or moderate, short-term hyperglycaemia. Blood glucose levels were elevated 4-fold by continuous i.v. infusion of D-glucose (4.8 g/kg/60 min). To determine whether the effects of hyperglycaemia on tumour blood flow involved increased rates of glycolysis and lactic acid production, galactose, a sugar not metabolized by the tumour, was administered using the same dose schedule. Hyperglycaemia was accompanied by a 3-fold increase in blood lactate levels and a slight hypervolaemic haemodilution without any significant systematic changes of the arterial blood pressure or respiratory b…
The influence of tumor blood flow and microenvironmental factors on the efficacy of radiation, drugs and localized hyperthermia.
1997
It is generally accepted that tumor blood flow, microcirculation, oxygen and nutrient supply, tissue pH distribution, and the bioenergetic status-factors which are usually closely linked and which define the so-called metabolic microenvironment--can markedly influence the therapeutic response of malignant tumors to conventional irradiation, chemotherapy, other nonsurgical treatment modalities, and the cell proliferation activity within tumors. Currently available information on the parameters defining the metabolic micromilieu in human tumors is presented in this review. According to these data, significant variations in these relevant factors are likely to occur between different locations…
Pathophysiological aspects of hyperthermia
1992
Blood flow in many rapidly growing tumors is sluggish leading to an impairment of convective heat dissipation which facilitates tumor heating compared to normal tissues. In addition, the compromised microcirculation causes a hostile metabolic micromilieu which can modulate the therapeutic effect of heat. After clinically relevant heat doses, a shut-down of tumor microcirculation is often observed creating a “heat-reservoir” and aggravating tumor hypoxia, acidosis, and substrate and energy depletion, factors which are known to greatly enhance tumor cell killing by heat. Since the mechanisms described are mostly derived from experimental results on fast-growing animal tumors, the clinical rel…
Pathophysiology of Tumors in Hyperthermia
1988
The response of tumor cells to hyperthermia is critically influenced by a number of pathophysiological factors both in vitro and in vivo. The most relevant factors in this context are tumor blood flow, tissue oxygenation, the energy status, and the pH distribution, which in turn define the cellular microenvironment.