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.

Complete local tumor remission after therapy with extra-corporeally applied high-energy shock waves (HESW)

High-energy shock waves (HESW) have recently been proposed as a means of non-invasive tumor therapy. Here we report the first successful local treatment of experimental tumors by means of multifocal and reported application of HESW. The experiments were performed on 29 Syrian golden hamsters bearing amelanotic hamster melanomas in the dorsal skin. HESW, generated electrohydraulically, were applied multifocally to the center and to 5 sites on the margin of the tumors. A group of animals undergoing surgical resection and an untreated group served as controls. Complete remission of local tumor was achieved in more than 90% of the HESW-treated hamsters and in the same number of surgically treated animals, while untreated tumors continued to grow. Frequency of metastasis was the same in both groups after HESW treatment or surgery. Tumor therapy with multifocally and repeatedly applied HESW was thus as successful as surgery.

Tumour localisation kinetics of photofrin and three synthetic porphyrinoids in an amelanotic melanoma of the hamster

In this study the localisation of porphyrinoid photosensitizers in tumours was investigated. To determine if tumour selectivity results from a preferential uptake or prolonged retention of photosensitizers, intravital fluorescence microscopy and chemical extraction were used. Amelanotic melanoma (A-Mel-3) were implanted in a skin fold chamber in Syrian Golden hamsters. Distribution of the porphyrin mixture Photofrin and three porphycenes, pure porphyrinoid model compounds, was studied quantitatively by intravital fluorescence microscopy. Extraction of tissue and blood samples was performed to verify and supplement intravital microscopic results. Photofrin accumulated in melanomas reaching a maximum tumour:skin tissue ratio of 1.7:1. Localisation of the different porphycenes was found to be highly tumour selective (3.2:1), anti-tumour selective (0.2:1), and non-selective (1:1) with increasing polarity of the porphycenes. The two non-tumour selective porphycenes had distinctly accelerated serum and tissue kinetics; serum halflife times being as short as 1 min. The specific localisation of the slowly distributed, tumour selective photosensitizers, occurred exclusively during the distribution from serum and uptake into tissues. For the most selective porphycene, the tumour selection process had a halflife of 260 +/- 150 min and led to a strongly fluorescent tumour edge edema. Accumulation of porphyrines by the amelanotic melanoma (A-Mel-3) can be attributed to an enhanced uptake rate for lipophilic molecules in this subcutaneously growing neoplasm. The slow distribution of the two tumour specific photosensitizers and the strong fluorescence of these hydrophobic molecules in the tumour compartment with a high water content indicate a carrier role of serum proteins in the selection process. Enhanced permeability of the tumour vasculature to macromolecules appears to be the most probable reason for the tumour selectivity of these two sensitisers.

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.

Acute effects of shock waves on tumors assessed by magnetic resonance imaging. Possible role of blood flow reduction

RATIONALE AND OBJECTIVES

The effects of shock waves on experimental tumors in vivo by gadolinium(+)-DTPA-enhanced magnetic resonance imaging (MRI) are assessed.

METHODS

Two amelanotic hamster melanomas were implanted in the dorsal skin of 19 hamsters. In experiment 1 (n = 7), MRI of untreated tumors was performed before, and 5 and 15 minutes after intravenous injection of Gd(+)-DTPA. In experiment 2 (n = 12), 200 shock waves were applied on one of the implanted tumors. Magnetic resonance imaging was performed 15 minutes after treatment before, and 5 and 15 minutes after injection of Gd(+)-DTPA.

RESULTS

In experiment 1, signal intensities (SI) of untreated tumors increased after injection of Gd(+)-DTPA. In experiment 2, enhancement was significantly delayed in shock-wave-treated tumors as compared with controls. Histology of the treated tumors revealed vascular damage.

CONCLUSION

Differences in enhancement between shock-wave-treated and control tumors after injection of Gd(+)-DTPA are interpreted as the consequence of reduced and delayed accumulation of Gd(+)-DTPA in treated tumors due to shock wave induced vascular damage and reduced tumor perfusion.

Quantitative analysis of network architecture, and microhemodynamics in arteriolar vessel trees of the ventilated rabbit lung

An experimental model has been developed for morphometric and microhemodynamic analysis of discrete arteriolar networks in the ventilated lung. We implanted a transparent window into the right thoracic wall of anesthetized rabbits. Autologous red blood cells were labeled with FITC in vitro. Using a fluorescence video microscopic technique the vessels of superficial arteriolar networks were mapped and classified hierarchically. Networks were investigated under zone 2 conditions (alveolar > left atrial pressure) during continuous monitoring of macrohemodynamics. We comprehensively measured segment length, diameter (D) and branching pattern in the whole network. Microhemodynamic parameters (red blood cell flux (Frbc), red blood cell velocity (Vrbc) and microhematocrit (H mu) were determined in terminal branches. As a result of network analysis the branching rules were found to be similar to those found by cast techniques in human and cat lungs. In terminal arterioles D (21 +/- 4 microns), Frbc (1472 +/- 662 cells/s), Vrbc (863 +/- 250 microns/s) and H mu (0.28 +/- 0.067) were heterogeneously distributed. Geometric, as well as microhemodynamic parameters fitted best to a lognormal distribution. This study represents an example of in vivo analysis of discrete microvascular networks. The measurements in hierarchically equivalent segments of pulmonary arteriolar vessel trees have been shown to be appropriate for estimation of topological, geometrical and microhemodynamic heterogeneity in pulmonary arteriolar networks.

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.

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.

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.

Angiogenesis, microvascular architecture, microhemodynamics, and interstitial fluid pressure during early growth of human adenocarcinoma LS174T in SCID mice

To date, most quantitative information on tumor angiogenesis, microcirculation, and transport has been derived from rodent tumors grown in transparent chamber preparations. In this paper we present a chamber technique adapted to immunodeficient mice for the study of human tumor xenografts. Microcirculatory parameters in severe combined immunodeficient mice bearing a dorsal skin fold chamber preparation were quantified using intravital microscopy and image analysis. The take rate of the human colon adenocarcinoma LS174T in the chamber preparation was 100%, and the tumor area doubling time was 6.5 days. Three days following implantation of 2 x 10(5) tumor cells onto the striated skin muscle, capillary sprouts were noted in the tumor cell mass. Microvasculature in the tumors was established after 10 days. Capillary density, vessel diameter, red blood cell velocity, and blood flow rates in individual microvessels measured on days 10, 14, 18, and 22 showed no statistical difference in the striated muscle (capillaries) and subcutaneous tissue (arterioles and venules) of the skin of tumor-free animals (N = 6), whereas these parameters increased slightly, but not significantly, in the LS174T tumors (N = 7). Mean interstitial fluid pressure (+/- SD) in these small tumors was 4.6 +/- 1.7 mmHg (N = 4) on day 10 and 5.1 +/- 0.9 mmHg (N = 4) on day 22 and significantly elevated compared to that in the subcutaneous and skin tissue (-0.9 +/- 0.8 mmHg) (N = 4) (P < 0.001). To our knowledge, this is the first model enabling intravital microscopic studies of human tumor xenografts in a transparent chamber preparation in severe combined immunodeficient mice. Studies on angiogenesis, microcirculation, and transport using such a preparation should provide new insights into microcirculation-mediated mechanisms for cancer treatment.

An experimental model for simultaneous quantitative analysis of pulmonary micro- and macrocirculation during unilateral hypoxia in vivo

An experimental model was developed for quantitative analysis of pulmonary microcirculation using in vivo fluorescence videomicroscopy during unilateral hypoxia induced by one-lung ventilation (1 LV). In five white New Zealand rabbits, pulmonary arterioles on the surface of the right lung were visualized by means of intra-arterial injection of FITC-labeled erythrocytes and FITC-Dextran. During 1 LV of the left lung, the mean airway pressure in the right lung was kept at the level of two-lung ventilation (2 LV) by means of N2-CPAP. Arteriolar diameters as well as parameters of macrocirculation (AP, CVP, PAP, LAP, CO) and gas exchange (paO2, Qs/Qt) were measured simultaneously during 2 LV and 1 LV. FiO2 was kept constant at 1.0 during both experimental phases. Macrohemodynamic parameters during 1 LV did not differ from those measured during 2 LV. 1 LV induced a significant decrease in paO2 (213 +/- 105 versus 427 +/- 22 mm Hg, P < 0.05) and a significant increase in Qs/Qt (22 +/- 7 versus 13 +/- 2%, P < 0.05). During 2 LV (baseline), the pulmonary arteriolar diameters ranged from 15-120 microns. 1 LV resulted in a significant decrease of arteriolar diameters to 89.0 +/- 9.3% of baseline (P < 0.05). Relative changes in arteriolar diameters were similar for vessels with baseline diameters of 0-40, 40-60, and 60-120 microns (88.4 +/- 9.9%, 89.6 +/- 9.4%, and 88.4 +/- 8.7%, respectively). The present model is the first one allowing in-vivo investigation of HPV during 1 LV and 2 LV on the basis of simultaneous measurement of pulmonary arteriolar diameters and macrocirculatory parameters in vivo. Although PAP and PVR did not change significantly, a reduction of pulmonary arteriolar diameters was proven in response to alveolar hypoxia during 1 LV. We suggest the model to be useful in studying the physiological effects of HPV on macro- and microcirculation as well as investigating pathophysiological and pharmacological influences on HPV.

Pixel-to-pixel correlation between images of absolute ATP concentrations and blood flow in tumours

Iodo(14C-)antipyrine autoradiography and imaging bioluminescence have been combined to obtain pixel-to-pixel correlations between absolute values for local blood flow and ATP concentrations at a microscopical level within designated areas in hamster melanomas. Positive pixel-to-pixel correlations were obtained in 4 of 6 tumours. Both flow and ATP values were less in mostly necrotic than in mostly viable tumour regions. The data provide evidence for the energetic state of cancer cells being strongly influenced by the efficiency of tumour microcirculation in several but not in all malignancies investigated.

Simultaneous high-resolution measurement of adenosine triphosphate levels and blood flow in the hamster amelanotic melanoma A-Mel-3

BACKGROUND

Some studies suggest that nutritional blood flow and intratumor levels of high-energy phosphates such as adenosine triphosphate (ATP) affect tumor response to treatment. Reports of intratumor variabilities have shown that distribution of high-energy phosphates within experimental and human tumors is not uniform, and this variability may be related to differences in blood flow in different regions of the tumor. However, previous studies provide no insight into the intratumor relationship of these parameters.

PURPOSE

To study the intratumor relationship between blood flow and ATP concentration, we have developed a method that allows simultaneous quantitation of the two variables almost at a cellular level at adjacent sites. In addition, this technique, which uses digital image processing and analysis, facilitates regional high-resolution measurements of blood flow and ATP concentrations in relation to histology.

METHODS

We examined tissue samples cut in consecutive order from one representative hamster A-Mel-3 amelanotic melanoma. Specimens from the same tumor were analyzed for histological features, blood flow (measured autoradiographically by the use of [4-N-methyl-14C]iodoantipyrine), and ATP content (measured by a quantitative substrate-induced bioluminescence reaction, using single-photon imaging). The data on the three parameters were stored as digitized images, which were later transformed to reach geometric congruency. The relationship between blood flow and ATP was examined by nonlinear regression and correlation analyses.

RESULTS

Regional distribution of blood flow was highly correlated with distribution of ATP within the A-Mel-3 tumor. For images of the tumor using measuring fields of approximately 20 tumor cells, the coefficient of correlation was .92 (P < .001). The relationship between the two parameters was described by a second-order function. At low blood flow values, small differences in blood flow were associated with large changes in levels of ATP, whereas at high blood flow values, differences in blood flow were associated with much smaller changes in ATP levels.

CONCLUSION

This high-resolution technique may have applications in future studies investigating the relationship between tumor cell metabolism and regional blood flow and in studies aimed at identifying the locoregional target of various cancer therapies.

Interstitial hypertension in head and neck tumors in patients: correlation with tumor size

Elevated interstitial fluid pressure (IFP) is associated with poor blood supply and inadequate delivery of drugs to solid tumors. IFP was measured in squamous cell carcinomas of the head and neck region in humans using the wick-in-needle technique. In all lesions (n = 19), the IFP was elevated (4-33 mm Hg). Furthermore, the IFP increased with tumor size. The highest IFP was 33 mm Hg in a 24-ml tumor. In one tumor, the IFP was found to be negative (-2.6 mm Hg), which is comparable to that in human skin or subcutaneous tissue. The histopathology of this tumor was benign. If this pressure difference between malignant and benign lesions can be confirmed in a large number of tumors, then the IFP could be used to aid tumor detection during needle biopsy. The value of IFP as a predictor of response to radiotherapy, photodynamic therapy, hyperthermia, and chemotherapy should be assessed prospectively.

Dilation of coronary microvessels by adenosine induced hypotension in dogs

An experimental model was established for fluorescence video microscopy of coronary microvessels. Nineteen dogs were anesthetized with a narcotic. Catheters were placed for hemodynamic monitoring and sampling of arterial and coronary venous blood. Myocardial perfusion was measured with radioactive microspheres. Following thoracotomy, movements of the myocardial surface area under investigation were restricted by a specially designed heart holder. Plasma was stained with FITC labelled dextran. Diameters were determined in arteriolar and venular microvessels greater than or equal to 20 microns. Measurements were performed during baseline conditions, i.e. only the basic anesthetic drug was applied, and during coronary vasodilation by continuous infusion of adenosine in a randomized sequence. Mean arterial pressure was reduced from 85 +/- 2 mmHg during baseline to 59 +/- 1 mmHg by infusion of 16.9 +/- 2.2 mg.kg-1.h-1 adenosine. Adenosine increased left ventricular blood flow by 253%, left ventricular oxygen demand remained unchanged. A total of 495 arteriolar and 170 venular diameters were measured during baseline condition and during adenosine infusion. Arteriolar diameters increased in all vessel segments between 20 and 600 microns, however, arterioles below a critical size of 100 microns had a greater dilating capacity than larger arterioles. Maximal decrease of segmental resistance occurred in 20-40 microns arterioles and amounted to 74%, which is less than the 82% decrease of total coronary resistance. Venular diameter changes, too, were more pronounced in smaller vessels.

Interstitial fluid pressure in solid tumors following hyperthermia: possible correlation with therapeutic response

Elevated interstitial fluid pressure (IFP) of tumors may be a physiological barrier to the delivery of certain therapeutic agents. The objective of this study was to find out if IFP could be lowered using localized hyperthermia and if the reduction in IFP could predict the tumor response to treatment. Amelanotic melanoma (A-Mel-3) implanted into the dorsal skin of Syrian golden hamsters was exposed to hyperthermic treatment after 7 days of tumor growth at tumor volumes of about 100-150 mm3. Hyperthermia was induced by immersing the tumor in a water bath at 43 degrees C for 30 or 60 min. Forty-eight h later the IFP of control and treated tumors was determined by using the wick-in-needle technique. The mean IFP in control tumors was 12.6 mmHg. Hyperthermic treatment for 30 min induced a significant decrease to 2.8 mmHg (P less than 0.001 versus controls), whereas a 60-min immersion of the tumors induced a further decrease to 0.8 mmHg (P less than 0.05 versus 43 degrees C for 30 min). Separate experiments on tumor growth in corresponding groups of animals revealed a significant growth delay of 2.7 days after hyperthermia for 30 min. Enhanced growth delay and partial tumor response in 66% of the tumors were found following 60 min of hyperthermia at 43 degrees C. The thermal dose-dependent decrease in IFP presumably results from the dose-dependent damage to the tumor vasculature. In addition, the association of an enhanced biological effect with a more pronounced reduction of interstitial fluid pressure suggests that the IFP might serve as a quantitative parameter to predict the response of tumors to hyperthermic therapy.

Myocardial oxygenation and transmural lactate metabolism during experimental acute coronary stenosis in pigs

Measurement of surface tissue pO2 (ptO2) with surface electrodes is increasingly applied in experimental medicine. Its use on the beating heart may seem to be problematic because transmural gradients of tissue pO2 would reduce the validity of pO2 determinations in the epicardial layers. This study attempted to determine whether ptO2 may be a valid and sensitive indicator of transmural myocardial oxygenation. In order to measure ptO2, two eight-channel Clark-type electrodes were placed on a beating porcine left ventricle (n = 13). Measurements were made at different degrees of acute stenosis of the left anterior descending artery (LAD). A 24-F cannula was inserted into the great cardiac vein, draining the poststenotic myocardium to obtain coronary venous blood samples. Transmural metabolic changes were detected simultaneously by coronary venous blood gas parameters and lactate levels. Epicardial tissue pO2 was 49 +/- 2 mm Hg (mean +/- SEM) before stenosis and decreased to a mean value of 25 +/- 2 mm Hg during stenosis. Different degrees of LAD stenosis (ptO2 range: 12-35 mm Hg) were substantial enough to alter arterio-coronary venous lactate difference (avd lactate) from +0.31 +/- 0.07 mmol/l (control) to -0.62 +/- 0.15 mmol/l (stenosis). A significant linear correlation between changes of ptO2 (delta ptO2) and changes of avd lactate (delta avd lactate) resulted (y = 0.59 + 0.62x; r = 0.86; p less than or equal to 0.001). However, linear regression analysis between delta ptO2 correlated with the corresponding data from coronary venous pO2 (delta pO2cv) oxygen content (delta O2contcv), and oxygen saturation (delta O2satcv) showed no significant correlations. We conclude that measurement of ptO2 is a sensitive and valuable indicator of transmural oxygenation in ischemic myocardium, whereas pO2cv, O2contcv and O2satcv do not seem to be valid predictors of ischemia in myocardial oxygenation.

[Selective hematoporphyrin derivative (HMD) application in arterial vessels using a porous balloon catheter results in equivalent levels as compared to high-dose systemic administration]

The treatment of atherosclerotic vascular stenosis with percutaneous angioplasty is limited by a rate of restenosis of about 20-40%, in spite of new angioplasty devices. Histological and immune histological examinations of restenosed material obtained by coronary atherectomy indicate that cellular proliferation is an important determinant of restenosis. With the use of photodynamic therapy (PDT), it might be possible to selectively impair proliferating tissue by the application of the photosensitizer Photofrin II (a hematoporphyrin-derivative, HPD) followed by localized laser-light radiation. With the knowledge of the success of PDT in tumor therapy, the extension of the application of PDT in prophylaxis of restenosis should be examined. The technique used up to now works with the systemic application of the sensitizer. By applying HPD locally, however, one might be able to reduce the amount of the photosensitizer, but still achieve an equally cytotoxic effect. A recently developed catheter with a porous balloon enables local application of HPD. The following study describes the uptake and distribution of the hematoporphyrin-derivative Photofrin II within the walls of elastic and muscular type vessels after systemic and selective application. In 20 rabbits and seven pigs, Photofrin II was applied systemically (5 mg/kg i.v.) and locally (5 ml of 2.5 mg/ml). From each animal 12 vascular specimens (six arterial segments of either muscular and elastic type) were removed at a definite time within a defined period of 5 min to 24 h after application. To quantify the uptake of Photofrin II, we used fluorescence microscopy with digital image processing. After systemic application there was an increase of Photofrin II over a 4-h period. In contrast, a maximum concentration of Photofrin II was measured immediately after local application and found to be decreasing over a period of 4 h. The intima showed the highest uptake of HPD, both after local and systemic applications, as compared to uptake by the media and adventitia. The intimal uptake was significantly higher after local than after systemic application. Media and the adventitia showed, respectively, only one-half and one-fifth of the intima's intake. The rapid increase of the HPD concentration after local application would make PDT feasible in restenosis prophylaxis immediately after angioplasty without systemic side-effects of the photosensitizer.

[Uptake and distribution of hematoporphyrin derivatives (HPD) in arteriosclerotic and normal vessel segments]

Percutaneous treatment of vascular disease is limited by a relatively high long-term restenosis rate. Proliferation of smooth muscle cells may be one of the major reasons for restenosis. Therefore, due to its selective cytotoxic effect, photodynamic therapy (PDT) with HPD-injection and local laser light-application might be a promising therapeutic principle as prophylaxis of restenosis. Up to now, PDT has been used clinically in the treatment of superficial tumors. We studied its potential application as an antiproliferative modality for restenosis prophylaxis. Basic conditions for therapeutic use are: uptake of HPD in arteriosclerotic vessels; arteriosclerotic lesions show a higher photosensitivity than normal vessel after application of HPD. We investigated the uptake of HPD (Photofrin II) in normal (n = 15) and arteriosclerotic (primary lesions n = 52; restenosis n = 10) human vessel segments using quantitative fluorescence detection after incubation with 2.5 micrograms and 5 micrograms HPD/ml cell culture medium. HPD content, as reflected by fluorescence intensity, was measured after 15, 30, 60 min, and 24 h of incubation. Fluorescence intensity was concentration-dependent, with 80% of the maximal uptake reached at 1 h. A preferential uptake of HPD was measured in arteriosclerotic as compared to normal vessel segments (primary lesion: fluorescence-ratio of 3:1 at 1 h; restenosed lesion: fluorescence-ratio of 4:1 at 1 h). In addition, highly cellular plaque segments like restenosed material showed markedly increased fluorescence as compared to acellular matrix. Uptake of HPD was quickly (within 1 h) and preferentially detected in arteriosclerotic segments. A selective cytotoxic effect when combined with laser light may result and could be applied to restenosis prophylaxis.

Oleic acid induced pancreatitis in pigs

An experimental model of edematous pancreatitis in pigs was established and measurement of pancreatic macro- and microcirculatory parameters and determinations of pancreatic enzymes (lipase, phospholipase A) and vasoactive mediators (prostanoids, kallikrein, kininogen) were performed. During general anesthesia the pancreas was isolated in situ. Pancreatic microcirculatory parameters were measured using videofluorescence microscopy after iv administration of FITC-Dextran. In hourly collected samples lipase and phospholipase A activities were determined enzymatically, concentrations of kallikrein, kininogen, and selected prostanoids were measured by radioimmunoassay. Two experimental groups were studied: (1) control (n = 9); (2) edematous pancreatitis induced by injection of oleic acid into the pancreatic artery (free fatty acid, ffa; n = 10). The animals were followed up for 6 hr. Systemic hemodynamic parameters remained constant in both groups. In the pancreatitis group pancreatic blood flow and O2-consumption decreased significantly (-55 and -49%), while pancreatic vascular resistance increased significantly (+50%). During baseline conditions 41% of all capillaries were perfused. In the pancreatitis group there were both areas with persistent stasis as well as areas with continuous perfusion. However, in the latter areas the portion of perfused capillaries decreased significantly to 27%. In the control group the portion of perfused capillaries remained constant. Liberation of lipase and phospholipase A especially into lymph and ascites fluid was measured during pancreatitis. Furthermore, considerable releases of kallikrein into lymph (+50%) and ascites (+800%) and a marked consumption of kininogen in lymph (+90%) and in ascites fluid (+80%) were measured. Activation of the arachidonic acid cascade and a significant release of prostacyclin and thromboxane A2 into pancreatic venous blood and lymph was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of arachidonic acid metabolites during acute pancreatitis in pigs

The pancreatic release of arachidonic acid metabolites was studied in a porcine model of acute pancreatitis. In situ isolation of the pancreatic gland enabled selective collection of pancreatic venous blood, pancreatic lymph, and ascites fluid. Three experimental groups were studied: 1) control (n = 9); 2) hemorrhagic pancreatitis induced by injection of 5% bile salt (sodium taurocholate) into the pancreatic duct (n = 10); and 3) edematous pancreatitis induced by injection of free fatty acid (FFA) into the pancreatic artery (n = 10). Determinations of cyclooxygenase metabolites were performed by radioimmunoassay; lipoxygenase metabolites (LTC4, LTD4) were measured by radioimmunoassay after purification by high-performance liquid chromatography. Prostaglandin (PG)F1 alpha, thromboxane B2, and PGF2 alpha concentrations were almost doubled in the lymph of the FFA group during pancreatitis, as were PGF1 alpha levels in pancreatic venous blood. However, concentrations of cyclooxygenase metabolites remained unchanged in the control group and in the bile salt group. Concentrations of LTC4 and LTD4 in lymph and ascites fluid of both pancreatitis groups increased from about 50 pg/ml to a mean level of 600 pg/ml at 6 h. Leukotriene concentrations in the control group were consistently below 50 pg/ml. The results of this study indicate that above all LTC4 and LTD4 are released from the organ and that these arachidonic acid metabolites may be also involved in the events following acute pancreatitis contributing to the systemic effects of the disease.

[Gd-DTPA-supported magnetic resonance tomographic perfusion follow-up of shockwave-treated tumors]

The signal characteristics of 14 shockwave-treated and 14 solid control tumors were studied before and after injection of Gd-DTPA in an animal model. T1-weighted images of shockwave-treated tumors documented no significant signal intensity increase after contrast media injection in comparison with the untreated control tumors. The reduction of perfusion in shockwave-treated tumors can be documented in vivo by the signal intensity changes of the tumors after contrast media injection.

Regional blood flow and tissue oxygen pressures of the collateral-dependent myocardium during isoflurane anesthesia in dogs

The authors investigated the effects of isoflurane on blood flow and tissue oxygen pressures of a collateral-dependent myocardium. Seventeen dogs divided into two groups were studied 3-4 weeks after implantation of ameroid coronary artery constrictors to completely occlude the proximal part of the left anterior descending artery. Experiments were performed during anesthesia with an opiate that was infused intravenously throughout the experiments. In Group 1 (n = 9), measurements were obtained during control and during isoflurane- (1.6-2.2 vol%) induced hypotension (mean arterial pressure, 60 mmHg). In Group 2 (n = 8), the identical protocol was applied, but norepinephrine was infused to maintain normotension. Dipyridamole effects were studied in five animals of Group 2 after a second control period at least 1 h after discontinuation of isoflurane. Isoflurane-induced hypotension caused reductions of blood flow and surface tissue oxygen pressures in the collateral flow-dependent area. Vasodilation in the normal left ventricular areas was demonstrated by an unchanged blood flow despite a reduced oxygen consumption and by a significantly increased coronary sinus hemoglobin oxygen saturation. When arterial pressure was maintained at its control level by norepinephrine, tissue oxygen pressures remained constant and collateral as well as normal area flow increased significantly during isoflurane. Coronary vascular resistance was lower during administration of isoflurane and norepinephrine compared with that during isoflurane induced hypotension, suggesting a significant contribution of tissue oxygen demand in regulation of coronary vascular resistance. At comparable levels of arterial pressure and left ventricular oxygen consumption, normal zone blood flow was significantly higher during dipyridamole than during isoflurane and norepinephrine. Thus, isoflurane-induced hypotension decreased blood flow and tissue oxygen pressures of collateral flow-dependent myocardial areas. However, neither isoflurane nor dipyridamole caused such alterations when arterial pressure was normal.

Left ventricular oxygen tensions in dogs during coronary vasodilation by enflurane, isoflurane and dipyridamole

The purpose of this study was to investigate the effects of the anesthetics enflurane and isoflurane and of the coronary vasodilator dipyridamole on myocardial oxygen balance and myocardial tissue oxygen tensions. The studies were performed in 24 open-chest dogs during basal anesthesia with a narcotic. Myocardial blood flow (MBF) was measured using radioactive microspheres, myocardial surface tissue PO2 by means of a platinum multiwire surface electrode. One control group and three experimental groups were studied: enflurane (1.1 vol%), isoflurane (0.7 vol%, both end-tidal concentrations), and dipyridamole (0.4 mg/kg). Mean arterial pressure significantly decreased to an average of 70 mm Hg in all three experimental groups. Although MBF was unchanged during enflurane (-18%) and isoflurane (+20%), it increased during dipyridamole (+304% p less than 0.05 vs baseline and control, enflurane, and isoflurane groups). Myocardial oxygen consumption decreased significantly during enflurane and isoflurane but remained unchanged during dipyridamole. Thus, the ratio between myocardial oxygen delivery and consumption increased 6% with enflurane (p less than 0.05 vs baseline), 47% with isoflurane (p less than 0.05 vs baseline and control group) and 280% with dipyridamole (p less than 0.05 vs baseline and control, enflurane, and isoflurane groups). Coronary venous PO2 remained unchanged during enflurane but increased significantly during isoflurane and dipyridamole. Left ventricular surface tissue PO2 was unchanged in enflurane and isoflurane animals and decreased slightly, yet significantly, during dipyridamole. All variables remained unchanged in the control group. Thus, isoflurane and dipyridamole interfered with MBF autoregulation and increased myocardial oxygen delivery out of proportion to myocardial demands.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial contractility, blood flow, and oxygen consumption in healthy dogs during anesthesia with isoflurane or enflurane

Left ventricular contractility (Vmax), myocardial blood flow (MBF), and oxygen consumption (O2C) were determined together with systemic hemodynamic parameters in a total of 21 mongrel dogs. Baseline recordings were obtained under basal anesthetic conditions with a narcotic (piritramid, IV). In the control group (n = 7), recordings were obtained during a three-hour observation period with infusion of piritramid. In experimental groups measurements were repeated with equi-anesthetic concentrations of isoflurane (0.7 and 1.4 vol%; n = 8) and enflurane (1.1 and 2.2 vol%; n = 6). Dose-dependent reductions of arterial pressure, cardiac output (CO) and peripheral vascular resistance were observed with isoflurane and enflurane. CO at the higher anesthetic level was depressed significantly more with enflurane. This difference was obviously due to a more severe depression of myocardial contractility with enflurane; Vmax was decreased by 18% and 26% with enflurane, but only by 10% and 17% with isoflurane (P less than 0.01). MBF and the fraction of CO received by the heart were increased above their baseline values with both concentrations of isoflurane. In contrast, the fraction of CO remained constant with enflurane while MBF decreased. O2C was reduced due to decreases of afterload and left ventricular contractility. The reduction was greater with enflurane than with isoflurane. All parameters remained unchanged in the control group. The results of this study indicate that the most striking difference in the actions of isoflurane and enflurane on cardiac parameters is on myocardial vascular resistance; MBF is increased with isoflurane, but is decreased with enflurane although myocardial perfusion pressure is reduced by almost identical amounts.(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboxane mediation of pulmonary hemodynamic responses after neutralization of heparin by protamine in pigs

Protamine neutralization of heparin is often associated with severe hemodynamic side-effects, including pulmonary hypertension and systemic hypotension. Because prostanoids may be involved, the authors studied the role of arachidonic acid metabolites, especially thromboxane A2, in this process. During anesthesia with enflurane and fentanyl, four groups of pigs were studied: Group 1 (n = 10) received heparin (250 IU/kg), followed by protamine (100 mg) after 15 minutes to neutralize the heparin. The same protocol was used in group 2 (n = 11), except that the thromboxane A2 receptor antagonist BM 13.177 (10 mg/kg) was infused 5 minutes before the protamine. The protocol for group 1 was also used for group 3 (n = 7) except that these animals were pretreated with indomethacin (10 mg/kg). Animals in group 4 (n = 10) were given protamine only (100 mg). Pulmonary artery pressure and pulmonary vascular resistance increased significantly in group 1 after protamine neutralization of heparin. This was accompanied by significant increases in plasma concentrations of the cyclooxygenase products thromboxane B2, 6-keto-prostaglandin F1 alpha, and prostaglandin F2 alpha. Cyclooxygenase products increased to comparable degrees in group 2, but without hemodynamic effects. Leukocyte counts decreased comparably in both groups. Hemodynamic reactions, as well as changes in plasma prostanoid levels were absent in group 3, and group 4, but leukocyte counts were less affected in animals that received protamine alone. The results indicate that the hemodynamic side-effects of protamine are mediated by prostanoids and that thromboxane A2 release is the pivotal step, because side effects were effectively prevented by pretreatment with a thromboxane receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Splanchnic oxygen consumption and hepatic surface oxygen tensions during isoflurane anesthesia

Blood flow to and oxygen consumption of the splanchnic organs were determined together with hepatic surface oxygen tensions in 18 mongrel dogs anesthetized with the long-acting narcotic piritramid. Twelve animals also received 0.7 Vol% and 1.4 Vol% isoflurane; six time-related controls received piritramid only. Surgical preparation consisted of a left thoracotomy for inserting a catheter into the left atrium for microsphere injections and for gaining access to the hepatic surface through an incision in the diaphragm. Parameters in the animals receiving isoflurane were recorded at three stages: stage 1--piritramid anesthesia after surgical preparation; stage 2-60 min after addition of 0.7 Vol% (end-expiratory) isoflurane; stage 3-60 min after addition of 1.4 Vol% (end-expiratory) isoflurane. Hepatic surface oxygen tension was determined at each stage using an eight-channel oxygen sensitive electrode. Mean arterial pressure and cardiac output decreased during both stages with isoflurane; hepatic arterial inflow remained constant. Portal blood flow and, hence, total hepatic inflow decreased significantly. An unchanged splanchnic O2 consumption induced lower hepatic venous pO2 values: 40 +/- 1 mmHg at control, 35 +/- 2 mmHg, and 31 +/- 2 mmHg (mean +/- SEM; both P less than 0.05) during isoflurane. A concomitant decrease of hepatic surface pO2 values indicated an altered tissue oxygenation. The percentage of hepatic surface pO2 values in the lowest pO2 range (0-5 mmHg) increased significantly from 8.4 to 20.3% during 1.4 Vol% isoflurane; the percentage of values of 0 mmHg increased from 2.4 to 9.8% during 1.4 Vol.%. No changes of these parameters were detected in the control animals during the 3-h observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Beneficial effect of cyclooxygenase inhibition on adverse hemodynamic responses after protamine

The hypothesis that adverse effects observed when heparin is antagonized by protamine are mediated by metabolites of the arachidonic acid cascade was tested during general anesthesia (enflurane, fentanyl) in 16 pigs classified into two groups. In the first group (n = 9), effects of intravenously administered protamine on systemic hemodynamics, blood/gas tensions, and arterial and mixed-venous prostanoid levels were studied. The second group (n = 7) was pretreated with indomethacin 10 mg/kg, and the same measurements were made. All pigs received heparin 150 units/kg. When protamine 1.1 +/- 0.1 mg/kg was administered over 3 minutes, marked hemodynamic alterations were observed in group 1: pulmonary artery pressure and pulmonary vascular resistance increased, and left ventricular end-diastolic and systemic arterial pressures decreased. Arterial and mixed-venous PO2 values deteriorated in all pigs in group 1 at the end of protamine infusion. These alterations were accompanied by significantly elevated prostanoid levels in arterial and mixed-venous plasma samples: Thromboxane A2, prostaglandin F2 alpha, KH2-PGF2 alpha (a metabolite of prostaglandin F2 alpha), and prostacyclin were maximally elevated at completion of protamine and remained significantly above control values at 5 minutes but were not significantly different from control after 10 minutes. Blocking the cyclooxygenase cascade by pretreatment of the pigs with indomethacin (group 2) prevented hemodynamic and blood gas alterations. It is concluded that in pigs the detrimental side effects associated with the use of protamine to reverse heparin are mediated by metabolites of the cyclooxygenase cascade.(ABSTRACT TRUNCATED AT 250 WORDS)