Biomedical subjects

G E Kuhnle

Publications and source records attributed to G E Kuhnle.

At least 19 recordsLinked to original sources

PubMed2000

Role of L-selectin in leukocyte sequestration in lung capillaries in a rabbit model of endotoxemia.

After a variety of pathophysiologic stimuli, neutrophils accumulate in lung capillaries and contribute to the pathogenesis of acute lung injury. Lung neutrophil sequestration has previously been attributed to mechanical retention of stiffened neutrophils, but L-selectin-mediated leukocyte/endothelial interaction may be an essential step. We investigated the effect of the anti-L-selectin antibody HuDreg 200 on leukocyte sequestration and microhemodynamics in alveolar capillaries in a model of acute endotoxemia. We used in vivo fluorescence microscopy to analyze kinetics of fluorescently labeled red and white blood cells in alveolar capillary networks of the rabbit lung. Investigations were performed over 2 h after an intravenous infusion of 0.2 ml/kg body weight (bw) NaCl, 2 mg/kg bw HuDreg 200, 20 microg/kg bw lipopolysaccharide (LPS) of Escherichia coli 0111:B4, or the combination of HuDreg 200 and LPS, respectively. Infusion of LPS induced leukocyte sequestration in alveolar capillaries, which was accompanied by a reduction of alveolar capillary perfusion and functional capillary density. These effects could be completely blocked by pretreatment of animals with HuDreg 200. We conclude that L-selectin-mediated leukocyte/endothelial interaction is a necessary prerequisite for leukocyte sequestration in alveolar capillaries in this model. Impaired alveolar capillary perfusion appeared to result directly from capillary leukocyte sequestration.

Acute Disease↗

PubMed2000

Measurement of respiratory impedance by impulse oscillometry--effects of endotracheal tubes.

Impulse Oscillometry is a new, noninvasive method to measure respiratory impedance, i.e. airway resistance and reactance at different oscillation frequencies. These parameters are potentially useful for the monitoring of respiratory mechanics in the critically ill patent with respiratory dysfunction. The endotracheal tube, used to mechanically ventilate these patients, however, represents an additional nonlinear impedance that introduces artifacts into the measurements. The objective of this work was therefore to investigate the effects of clinically available endotracheal tubes on resistance and reactance of an in vitro analogue of the respiratory system. Additionally, the effects of decreasing the compressible gas volume in this experimental model, as a simulation of decreased lung capacity and compliance, was investigated. Impulse oscillometric measurements of the test analogue gave highly reproducible results with and without an endotracheal tube. The tubes had significant influence on the measurement of the test object at all frequencies investigated. Changes of low frequent reactance were negligible - at least if repetitive measurements of the same system are performed - for realistic measurement of airway resistance, a correction of the tube impedance or measurement of the pressure distal of the tube is required. Resistance increased and low frequent reactance decreased significantly with decreasing gas volume. These changes were of magnitudes higher than the variations due to the introduction of the endotracheal tubes. Our results suggest that changes of respiratory reactance measured with impulse oscillometry may be used as a monitoring parameter in intubated patients.

Airway Resistance↗

PubMed1998

Microhemodynamics and leukocyte sequestration after pulmonary ischemia and reperfusion in rabbits.

OBJECTIVE: Investigation of leukocyte sequestration in alveolar capillaries and of microhemodynamic changes after pulmonary ischemia/reperfusion injury. METHODS: The kinetics of leukocyte passage and the hemodynamics in pulmonary microcirculation were investigated in 16 rabbits by intravital microscopy. Mean red blood cell velocity and the number of sticking leukocytes were measured in pulmonary arterioles, venules, and capillaries after 1 hour of tourniquet ischemia and 10 minutes and 1 hour after reperfusion. RESULTS: The decrease of red blood cell velocity after reperfusion was associated with a largely increased heterogeneity of blood flow. Immediately after the onset of blood flow, sequestered leukocytes were found in all microvascular segments. An increased number of leukocytes was present in arterioles, venules, and alveolar capillaries 10 minutes and 1 hour after reperfusion. Concomitantly, width of alveolar septa was increased while arterial oxygen tension was reduced, indicating the development of interstitial pulmonary edema. CONCLUSION: Leukocytes are sequestered after pulmonary ischemia and reperfusion not only in alveolar capillaries but also in arterioles and venules, and they may contribute to the development of reperfusion edema.

Animals↗

PubMed1998

Noninvasive measurement of regional cerebral blood flow by near-infrared spectroscopy and indocyanine green.

Clinicians lack a practical method for measuring CBF rapidly, repeatedly, and noninvasively at the bedside. A new noninvasive technique for estimation of cerebral hemodynamics by use of near-infrared spectroscopy (NIRS) and an intravenously infused tracer dye is proposed. Kinetics of the infrared tracer indocyanine green were monitored on the intact skull in pigs. According to an algorithm derived from fluorescein flowmetry, a relative blood flow index (BFI) was calculated. Data obtained were compared with cerebral and galeal blood flow values assessed by radioactive microspheres under baseline conditions and during hemorrhagic shock and resuscitation. Blood flow index correlated significantly (rs = 0.814, P < 0.001) with cortical blood flow but not with galeal blood flow (rs = 0.258). However, limits of agreement between BFI and CBF are rather wide (+/- 38.2 +/- 6.4 mL 100 g-1 min-1) and require further studies. Data presented demonstrate that detection of tracer kinetics in the cerebrovasculature by NIRS may serve as valuable tool for the noninvasive estimation of regional CBF. Indocyanine green dilution curves monitored noninvasively on the intact skull by NIRS reflect dye passage through the cerebral, not extracerebral, circulation.

Algorithms↗

PubMed1997

Contribution of selectins to leucocyte sequestration in pulmonary microvessels by intravital microscopy in rabbits.

1. Sequestration of leucocytes in the lung is the net result of leucocyte rolling and sticking in pulmonary arterioles and venules and their retention in alveolar capillaries. 2. In order to investigate whether adhesion molecules of the selectin family contribute to these phenomena the effects of fucoidin (an inhibitor of L- and P-selectin) on microhaemodynamics and leucocyte kinetic were studied in pulmonary arterioles, capillaries and venules by means of intravital fluorescence microscopy in a rabbit model. 3. Fucoidin reduced leucocyte rolling in pulmonary arterioles and venules by 75 and 83%, respectively, without affecting leucocyte sticking. In alveolar capillaries, fucoidin reduced leucocyte retention and accelerated leucocyte passage, thus reducing the alveolar transit time of leucocytes by 62%. 4. It is concluded that rolling of leucocytes in pulmonary microvessels is mediated by selectins, whereas sticking relies on selectin-independent mechanisms. 5. Leucocyte retention in alveolar capillaries is not due solely to mechanical hindrance of leucocyte passage through narrow vessel segments, as previously hypothesized, but also depends on interaction of leucocytes with the capillary endothelium.

Animals↗

PubMed1995

[The effect of mechanical ventilation, thoracotomy, and one-lung respiration on intrapulmonary perfusion distribution. An animal experimental study].

The physiological pattern of regional pulmonary blood flow is mainly determined by the relationship of pulmonary arterial, venous, and alveolar pressures. Changes in alveolar pressure and pulmonary geometry may therefore be expected to influence regional perfusion, which is a key determinant of pulmonary gas exchange. Unilateral thoracotomy is usually performed with the patient in the lateral decubitus position. The present study examined the influence of mechanical factors on regional pulmonary blood flow distribution in rabbits in the lateral decubitus position during normoxia and unilateral hypoxia. METHODS. Anaesthetised white New Zealand rabbits (n = 8) weighing 2200-3900 g (mean = 2860 g) received central venous injections of radioactive microspheres while in the left lateral decubitus position during spontaneous breathing (SB) and during mechanical ventilation (two-lung ventilation, 2LV), under closed (2LVC) and open chest (2LVT) conditions, as well as during unilateral hypoxia of the nondependent lung induced by nitrogen inflation (1LVN) or atelectasis (1LVA). The method used for one-lung ventilation (1LV) has been previously described in detail. Arterial, central venous, and pulmonary arterial pressures were recorded continuously. Lungs were excised, dried in the inflated state, and cut into 16 sagittal slices, which were further divided into lobar components, the lower lobes into center and periphery. The radioactivity of each specimen was measured in a gamma-counter; perfusion of the individual tissue specimens was quantified using the software program MIC III. The Friedman test followed by paired comparisons according to Conover was used for statistical analysis of differences between the experimental phases. Perfusion of central and peripheral parts of isogravitational slices was compared by use of the Wilcoxon matched pairs test. Values are given as means +/- SE; the level of significance was P < 0.05 unless otherwise indicated. RESULTS AND DISCUSSION. Haemodynamic parameters did not differ significantly between the experimental phases (Table 1). Compared to 2LV, a significant increase in venous admixture (P < 0.05) and a corresponding decrease in PaO2 (P < 0.01) were observed during 1LV. This effect was significantly more pronounced during 1LVA as compared to 1LVN (P < 0.01). Since inspiratory pressure was kept constant throughout the experiments, moderate respiratory acidosis developed during both phases of 1LV. Regional perfusion (Qr) of the nondependent lung was slightly reduced during 2LVC compared to SB and 2LVT. One-lung ventilation induced a significant decrease in perfusion of the hypoxic lung (P < 0.001 1LVN, 1LVA vs. SB,2LVC,2LVT). In accordance with the data obtained from blood gas analysis and oximetry, this effect was more pronounced during N2 insufflation than during atelectasis (P < 0.01 1LVN vs. 1LVA). Among the factors that may account for this effect, PaCO2 did not differ significantly between both phases of 1LV. During N2 insufflation PO2 at the hypoxia-sensitive site is lower than during atelectasis, where it equals mixed-versus PO2 (PvO2). The difference in local PO2 is unlikely, however, to have caused the changes in regional perfusion between 1LVN and 1LVA, since PvO2 was as low as 40 mmHg during 1LVA and the pulmonary vascular response to hypoxia has been found to reach its maximum in this PO2 range [2, 11]. Enhanced redistribution of regional perfusion during 1LVN as compared to 1LVA is therefore most likely attributed to differences in alveolar pressure and pulmonary geometry. Apart from a radial perfusion gradient in the right lower lobe during 2LVC and 2LVT, no isogravitational Qr gradients were observed. CONCLUSION. We conclude that controlled mechanical ventilation in the lateral decubitus position causes only minor changes in vertical blood flow distribution.

Animals↗

PubMed1995

Effects of photodynamic therapy on leucocyte-endothelium interaction: differences between normal and tumour tissue.

An inflammatory reaction is regularly noticed in irradiated tissues following photodynamic therapy (PDT). This observation is potentially associated with leucocyte-mediated tissue damage, which might further contribute to the tumoricidal effect of this therapy. The objective of our study was to investigate the effects of PDT on leucocyte-endothelium interaction in the microvasculature of tumours and normal tissue. Experiments were performed in the dorsal skinfold chamber preparation of Syrian golden hamsters bearing amelanotic melanoma A-Mel-3. The photosensitiser. Photofrin (5 mg kg-1 i.v.) was injected 24 h before laser irradiation (630 nm, 100 mW cm-2, 10 J cm-2 or 100 J cm-2). Post-capillary confluent venules (diameter 15-40 microns) of subcutaneous (s.c.) tissue or the amelanotic melanoma A-Mel-3 were observed by intravital microscopy before, 5, 30, 60 and 180 min after laser irradiation and recorded for off-line analysis. Before treatment, the number of adherent leucocytes in tumour vessels was only 22% of the number observed in vessels of s.c. tissue (P < 0.01). The maximum increase in adhering leucocytes was observed in post-capillary venules of s.c. tissue 1 h after PDT (P < 0.01). In contrast, enhanced leucocyte-endothelium interaction was missing in tumour vessels and in control groups. These results indicate that the tumour destruction observed after PDT is not mediated by leucocyte-endothelium interaction in the tumour. Induction of leucocyte adhesion in the PDT-treated normal tissue suggests a contribution to the peritumoral inflammatory response. Different maturational status or biochemical properties of tumour microvascular endothelium may explain the lack of leucocyte adherence upon PDT.

Animals↗

PubMed1995

Effects of isoflurane on regional pulmonary blood flow during one-lung ventilation.

Isoflurane has been reported to inhibit hypoxic pulmonary vasoconstriction. However, the effects of one-lung ventilation and isoflurane on regional pulmonary blood flow (Qr) have not been investigated in detail. Therefore, using radionuclide labelled microspheres we measured Qr in rabbits (n = 8) in the left lateral decubitus position during two- and one-lung ventilation under i.v. baseline anaesthesia and during additional administration of 1.5% isoflurane. Macrohaemodynamic variables were recorded continuously. Isoflurane increased non-dependent lung blood flow during two-lung ventilation. One-lung ventilation caused a homogeneous decrease in Qr throughout the hypoxic lung, irrespective of isoflurane administration (P < 0.001). However, isoflurane significantly augmented Qr of the hypoxic lung during one-lung ventilation (P < 0.05). During all phases, Qr of the upper lobe was higher compared with that in the lower lobe in isogravitational slices of both lungs; a ventrodorsal perfusion gradient was found in the left upper lobe. We conclude that 1.5% isoflurane increased perfusion of the non-dependent lung, inhibited hypoxic pulmonary vasoconstriction-induced redistribution of pulmonary blood flow and did not influence isogravitational perfusion gradients.

Anesthesia, Intravenous↗

PubMed1995

Effect of blood flow on the leukocyte-endothelium interaction in pulmonary microvessels.

Circulating leukocytes are retained in the microcirculation of the lung. The site of leukocyte retention, however, is still a subject of controversy, and the effects of microvascular blood flow on the leukocyte-endothelium interaction in pulmonary microvessels are unknown. We used in vivo fluorescence microscopy to analyze microhemodynamics and the flow behavior of in vivo-labeled leukocytes in pulmonary arterioles, venules, and alveolar capillaries. Microvascular blood flow was altered by variation of cardiac output. Leukocytes were found to roll and to stick on arteriolar and more pronouncedly on venular endothelium. During their passage through alveolar capillaries, a fraction of passing leukocytes became static for 0.1 to > 5 s. Under control conditions, leukocytes were concentrated approximately 8-fold more in arterioles and 24-fold more in venules than in the blood passing through these vessels. The concentration in capillaries was 1.5 times greater than in venules. The velocity of rolling leukocytes in arterioles and venules correlated significantly with the shear rate in these vessels, whereas the density of sticking cells was negatively correlated with the shear rate. The differences between leukocyte rolling and sticking in arterioles and in venules cannot be explained by respective hemodynamic conditions. In alveolar capillaries, the percentage of temporarily static leukocytes and the time of their stasis were inversely correlated with red-blood-cell (RBC) velocity. We conclude that leukocytes are retained in pulmonary arterioles, venules, and alveolar capillaries according to microvascular blood flow and endothelial factors.

Animals↗

PubMed1994

High-energy shock waves enhance hyperthermic response of tumors: effects on blood flow, energy metabolism, and tumor growth.

BACKGROUND: The ability to kill cancerous tissue by heating is often limited by heat lost to flowing blood. Recent studies demonstrate that high-energy shock waves (HESWs), when applied to solid tumors, destroy the tumor microvasculature and rapidly decrease blood flow. We hypothesized that impairment of tumor blood flow by HESWs might result in increased effectiveness of hyperthermia treatment. PURPOSE: The purpose of our work was to determine whether HESWs enhance the response of tumors to hyperthermia. METHODS: Seventy A-Mel-3 amelanotic hamster melanomas were exposed to either 700 HESWs (20 kV, 80 nanofarads), local hyperthermia (43.3 degrees C for 30 minutes), or a combination of both. Three, 12, or 24 hours later, tumor blood flow and adenosine triphosphate (ATP) concentrations were measured by [4-N-methyl-14C]iodoantipyrine autoradiography and quantitative ATP imaging bioluminescence, respectively. In separate experiments, the effects of the separate and combined treatments on tumor growth were studied in 52 animals. RESULTS: Combining HESWs and hyperthermia produced a significantly longer and more pronounced reduction of tumor and adjacent tissue perfusion than either HESWs or hyperthermia alone (P < .05). ATP concentrations were markedly reduced following HESW treatment alone and following the combined therapy compared with untreated controls (P < .05). Three hours after combined therapy, ATP concentrations were significantly below values measured after hyperthermia alone (P < .01). Tumor growth was delayed much more effectively by the combination of HESWs and hyperthermia than by either treatment alone (P < .001). Fifty-four percent of the animals receiving combined treatment showed complete local tumor cure over 52 days of observation, and 46% showed partial remission. CONCLUSION: The combination of HESWs and hyperthermia might be an effective new way of treating cancer, especially in patients who are not candidates for surgery. IMPLICATIONS: These results must be viewed cautiously, as the vasculature of human tumors seems to be less sensitive to hyperthermia than has been observed in experimental tumors.

Adenosine Triphosphate↗

PubMed1994

In vivo kinetics and spectra of 5-aminolaevulinic acid-induced fluorescence in an amelanotic melanoma of the hamster.

For successful photodynamic diagnosis (PDD) and effective photodynamic therapy (PDT) with the clinically used 'photosensitiser' 5-aminolaevulinic acid (ALA), knowledge of the maximal fluorescence intensity and of the maximal tumour-host tissue fluorescence ratio following systemic or local application is required. Therefore, time course and type of porphyrin accumulation were investigated in neoplastic and surrounding host tissue by measuring the kinetics and spectra of ALA-induced fluorescence in vivo. Experiments were performed in the amelanotic melanoma A-Mel-3 grown in the dorsal skinfold chamber preparation of Syrian golden hamsters. The kinetics of fluorescent porphyrins was quantified up to 24 h after i.v. injection of 100 mg kg-1, 500 mg kg-1 or 1,000 mg kg-1 body weight ALA by intravital fluorescence microscopy and digital image analysis (n = 18). In separate experiments fluorescence spectra were obtained for each dose by a simultaneous optical multichannel analysing device (n = 3). A three-compartment model was developed to simulate fluorescence kinetics in tumours. Maximal fluorescence intensity (per cent of reference standard; mean +/- s.e.) in the tumour arose 150 min post injection (p.i.) (1,000 mg kg-1, 109 +/- 34%; 500 mg kg-1, 148 +/- 36%) and 120 min p.i. (100 mg kg-1, 16 +/- 8%). The fluorescence in the surrounding host tissue was far less and reached its maximum at 240 min (100 mg kg-1, 6 +/- 3%) and 360 min p.i. (500 mg kg-1, 50 +/- 8%) and (1,000 mg kg-1, 6 +/- 19%). Maximal tumour-host tissue ratio (90:1) was encountered at 90 min after injection of 500 mg kg-1. The spectra of tissue fluorescence showed maxima at 637 nm and 704 nm respectively. After 300 min (host tissue) and 360 min (tumour tissue) additional emission bands at 618 nm and 678 nm were detected. These bands indicate the presence of protoporphyrin IX (PPIX) and of another porphyrin species in the tumour not identified yet. Tumour selectivity of ALA-induced PPIX accumulation occurs only during a distinct interval depending on the administered dose. Based on the presented data the optimal time for PDD and PDT in this model following intravenous administration of 500 mg kg-1 ALA would be around 90 min and 150 min respectively. The transient selectivity is probably caused by an earlier and higher uptake of ALA in the neoplastic tissue most likely as a result of increased vascular permeability of tumours as supported by the mathematical model.

Aminolevulinic Acid↗

PubMed1994

Isoflurane inhibits hypoxic pulmonary vasoconstriction. An in vivo fluorescence microscopic study in rabbits.

BACKGROUND: Contradictory results have been reported in previous studies investigating the effect of isoflurane on hypoxic pulmonary vasoconstriction by indirect approaches. The current study measured the effects of one-lung ventilation (1LV) and isoflurane 1.5% by direct visual observation of the pulmonary microcirculation. METHODS: Ten New Zealand White rabbits were anesthetized with intravenous thiopental, alpha-chloralose, and piritramid. Arterial, central venous, pulmonary arterial, left atrial, and airway pressures and cardiac output were recorded continuously. 1LV was facilitated by a bronchial blocker in the right main bronchus. A transparent window was implanted into the right thoracic wall for videofluorescence microscopy of the subpleural pulmonary microcirculation. After intravenous injection of fluorescein isothiocyanate-labeled red blood cells, vessel diameters, red blood cell flux, red blood cell velocity, and dynamic microhematocrit were measured in pulmonary arterioles and venules during two-lung ventilation and 1LV during baseline anesthesia and with supplementary isoflurane 1.5%. RESULTS: During intravenous anesthesia, 1LV caused significant reduction of vessel diameters and red cell flux and velocity and an increase in microvascular hematocrit in pulmonary arterioles and venules. The decreases in arteriolar diameters and red blood cell flux and velocity induced by 1LV were significantly attenuated by isoflurane as compared with those measured during baseline anesthesia (P = 0.010, P = 0.029 and P = 0.047). Accordingly, 1LV-induced reduction of venular red cell flux (P = 0.023) and velocity (P = 0.036) were less pronounced during isoflurane. Isoflurane caused a significant decrease in arterial pressure. Venous admixture increased and arterial oxygen tension decreased significantly during 1LV; the changes were more pronounced during 1LV with isoflurane 1.5% than during 1LV with baseline anesthesia. CONCLUSIONS: 1LV leads to a marked reduction of microvascular diameters and blood flow in the hypoxic lung. Isoflurane 1.5% inhibits hypoxic pulmonary vasoconstriction in pulmonary arterioles and increases regional blood flow in the hypoxic lung.

Anesthesia, Intravenous↗

PubMed1994

Leukocyte kinetics in pulmonary microcirculation: intravital fluorescence microscopic study.

To determine the site of sequestration of leukocytes in the lung, we investigated the kinetics of fluorescently labeled erythrocytes and leukocytes in pulmonary arterioles, venules, and alveolar capillaries in vivo by using fluorescence videomicroscopy. The subpleural pulmonary microcirculation of the ventilated rabbit lung was visualized via a transparent window implanted into the right thoracic wall. Fluorescein isothiocyanate-labeled erythrocytes were administered intravenously, whereas leukocytes were labeled in vivo by intravenous injection of rhodamine 6G. Rolling and adherence of leukocytes on the surface of the vessel walls were observed in arterioles as well as in venules. The median velocity of nonadherent leukocytes was significantly higher in arterioles than in venules (84 +/- 12 vs. 15 +/- 3% of erythrocyte velocity, respectively). In alveolar capillaries the majority of leukocytes were retained at distinct sites for periods of 0.1 to > 5 s (median 0.61 s). The relative velocity of leukocytes moving in capillaries was comparable to that determined in arterioles (80 +/- 9% of erythrocyte velocity). These measurements indicate that leukocyte sequestration in the lung is governed by the retention of leukocytes in capillaries and by the interaction of leukocytes with microvascular endothelium of arterioles and venules. We propose that the kinetics of these phenomena determine the equilibrium between circulating and sequestered leukocytes.

Animals↗

PubMed1993

High-energy shock waves induce blood flow reduction in tumors.

We have studied the effect of extracorporeally applied high-energy shock waves (HESW) on blood flow in amelanotic melanomas (A-Mel-3). Two tumors were implanted in the dorsal skin of 21 Syrian golden hamsters. One of the tumors was treated with 200 HESW, and the other served as an intraindividual control. Mean blood flow in the whole tumor, or the tumor excluding necrotic areas, was quantitatively measured using autoradiography with iodo[14C]antipyrine at 30 min (n = 5), 1 h (n = 5), 3 h (n = 5), and 12 h (n = 6) after HESW treatment. As measured for the whole tumor, blood flow in the controls was 23.4 +/- 7.9 ml/100 g/min (median +/- SE) and thus in the range reported in the literature. Thirty min or 1 h after the application of HESW, tumor perfusion was reduced to 6 +/- 4% or 5 +/- 4% (median +/- SE) of the corresponding controls, respectively. Three h after treatment, perfusion increased slightly to 7 +/- 5% and after 12 h increased significantly to 55 +/- 25% of the corresponding controls. Values measured excluding the necrotic areas were higher in all groups. Temporary reduction of tumor perfusion after treatment with HESW was interpreted as a consequence of HESW-induced damage to tumor microcirculation. These effects should be taken into account for maximizing the therapeutic efficiency of HESW on tumors and for combining HESW treatment with other therapeutical modalities.

Animals↗

PubMed1993

Relation between autoradiographically measured blood flow and ATP concentrations obtained from imaging bioluminescence in tumors following hyperthermia.

The effects of moderate local hyperthermia (43.3 degrees C/30 min) on regional blood flow and regional ATP distribution in the amelanotic hamster melanoma A-Mel-3 were investigated by high-resolution techniques. Blood flow and ATP concentrations were measured simultaneously in treated and untreated tumors and in adjacent tissues by means of (14C)-Iodoantipyrine autoradiography and quantitative imaging bioluminescence in consecutive tissue sections at 3, 12 and 24 hr following treatment. Digital image processing and the use of a special algorithm allowed the regional interrelationship of the 2 parameters to be quantified. Measurements revealed a great heterogeneity of blood flow and ATP between and within the tumors. A pronounced reduction of blood flow and ATP in tumors was observed after hyperthermia in comparison to untreated controls. The adjacent tissue remained mostly unaffected. However, a weakly positive relationship between the 2 parameters was obtained when variables were averaged in tumors or groups. At the microregional level, the untreated tumor tissue revealed a significant, positive correlation between nutritional blood flow and ATP concentrations. This local correlation was reduced and changed with time after treatment indicating different time courses of the parameters. Hyperthermia induced a sudden decrease in blood flow, later associated with a decline in ATP. A slight recovery of both parameters was observed 24 hr after hyperthermia. The results indicate that the metabolic status of the tumor cells is critically dependent on nutritional blood flow but also on the energy requirement of the individual tumor.

Adenosine Triphosphate↗

PubMed1993

Ischemia and loss of ATP in tumours following treatment with focused high energy shock waves.

High energy shock waves (HESW) have been reported to be cytotoxic to tumour cells in vitro and in vivo. For that reason they are evaluated as a new modality for cancer treatment. In the present study we have quantified the effect of treatment with multifocal HESW on tumour blood flow and energy status. Blood flow and adenosine triphosphate (ATP) concentration were investigated simultaneously in tumour and adjacent tissue of six treated and six untreated amelanotic hamster melanomas (A-Mel-3) at 3, 12 or 24 h after multifocal application of HESW. 14C-iodoantipyrine autoradiography for blood flow measurements and quantitative ATP imaging bioluminescence were employed. Following treatment, tumour blood flow and ATP concentration were significantly reduced, as compared to control, over the entire period of observation. Three hours after HESW, blood flow and ATP concentration were at the background level. In adjacent tissue, blood flow and ATP concentration were distinctly diminished. We therefore conclude that multifocal HESW induce a breakdown of tumour-, and adjacent tissue perfusion which is accompanied by a significant decrease of intracellular ATP concentration.

Adenosine Triphosphate↗

PubMed1993

Distribution of microvascular pressure in arteriolar vessel trees of ventilated rabbit lungs.

We have developed a new in vivo microscopic technique for comprehensive measurements of vessel diameter, segment length, and red blood cell velocity in discrete arteriolar vessel trees of the lung. In anesthetized and mechanically ventilated rabbits, a transparent window was implanted into the right thoracic wall. We injected fluorescently labeled red cells to visualize blood flow and to measure red blood cell velocity. The distribution of microvascular pressures was simulated in a computer model based on morphometric and microhemodynamic data. Of the total pulmonary vascular pressure drop from pulmonary artery to left atrium, on average 2.5% occurred in distal arteriolar vessel trees with main trunk diameters of 73-111 microns. Along the pathlength from main trunk to terminal arterioles (0.18-2.79 mm), the pressure drop ranged between 0.06 and 0.94 mmHg. The pressure drop along individual pathways correlated significantly with pathlength of terminal arterioles, whereas red blood cell velocity did not. The results indicate that in terminal arteriolar vessel trees of the ventilated rabbit lung the resistance to blood flow is low, and the heterogeneity of microvascular pressures in arterioles feeding capillary networks is high.

Animals↗

PubMed1993

Measurement of microhemodynamics in the ventilated rabbit lung by intravital fluorescence microscopy.

Pulmonary microhemodynamic parameters were directly measured along with systemic pressures and cardiac output in the ventilated rabbit lung. Subpleural arterioles and venules ranging from 10 to 35 microns luminal diameter were investigated under zone 2 conditions, i.e., during inspiratory plateau at an airway pressure of 8 mmHg. Mean arteriolar and venular diameters (24.6 +/- 3.3 and 21.9 +/- 3.6 microns, respectively), mean red blood cell (RBC) fluxes (1,549 +/- 501 and 1,257 +/- 600 cells/s), and mean RBC velocities (0.79 +/- 0.21 and 0.82 +/- 0.21 mm/s) were measured using a fluorescence video-microscopic technique. Calculated microhematocrit (Hct mu) was below systemic values (Hctsys) (Hct mu/Hctsys: arterioles, 0.75 +/- 0.12; venules, 0.67 +/- 0.08). The mean capillary transit time of RBC was 0.47 +/- 0.16 s over a mean arteriovenous distance of 173 +/- 70 m. Significant correlations were demonstrated between microhemodynamic parameters. A correlation among cardiac output, pulmonary arterial pressure, and RBC velocity demonstrates the connection between macro- and microhemodynamics in the rabbit lung. In conclusion, the present model is the first one enabling the measurements of the principal circulatory determinants for gas exchange, i.e., microvascular blood flow, Hct mu, and capillary transit time of RBCs in the ventilated rabbit lung under simultaneous macrocirculatory control.

Animals↗