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.

Dosage of inhaled nitric oxide: a simple method for experimental studies

Few studies on treatment with inhaled nitric oxide (NOi) have been carried out in small laboratory animals yet, since commercially available dosing devices are not appropriate in this setting for technical or financial reasons. The aim of our study was to establish and validate a simple, cost-effective system for the application of NOi in small animals. The system mixes NOi with constant-flow inspiratory gas. A gas blender allows for a mixture of nitrogen, oxygen, and NO dissolved in nitrogen. A formula using the desired inspiratory oxygen fraction and the desired concentration of NOi as independent variables derives a somewhat higher inspiratory oxygen fraction, which is preset using an oximeter. Then the flow of NO in nitrogen is started, lowering the inspiratory oxygen fraction to the initially desired value, thereby adding NOi in the desired concentration. The method was validated by 153 adjustments, covering a variety of oxygen fractions and concentrations of NOi. NOi was measured by chemiluminescence as reference method. A close correlation (R = 0.994) was found, and the regression line was close to the line of identity with y = -0.0994 + 1.048x. No systematic errors could be identified. We conclude that the method described may serve as a simple, cost-effective way to administer NOi to small animals.

Validation of MR thermometry technology: a small animal model for hyperthermic treatment of tumours

BACKGROUND

Local hyperthermia has been shown to be an effective adjuvant therapy for cancer. However, progress in this treatment modality requires the non-invasive assessment of temperature distribution in the entire tumour to enable administration of an efficient thermal dose to all tumour areas. Magnetic resonance (MR) imaging offers a promising tool to quantify, non-invasively and three-dimensionally, temperature distribution within tumours. An animal model taking into account the complex interrelationship between pathophysiological changes within a tumour during hyperthermia and temperature-sensitive MR parameters is warranted for the development and validation of new MR thermometry technology.

METHODS

An experimental set-up was implemented to allow simultaneous measurements of temperature, tumour blood flow and temperature-sensitive MR parameters under standardised conditions in vivo. Local hyperthermia was induced at 44 degrees C for 20 min under inhalation anaesthesia on seven Syrian Golden hamsters bearing an amelanotic melanoma. Fibreoptic probes were used for reference temperature measurements. Laser Doppler flowmetry served for on-line tumour blood flow determination, and MR thermometry was performed using longitudinal T1 relaxation time measurements.

RESULTS

The experimental design enables multifunctional MR thermometry. T1 relaxation times of tumours were 1.44 s (1.36, 1.46) and 1.53 s (1. 48, 1.75) at 37 degrees C and during hyperthermia at 44 degrees C, respectively (median, 25% and 75% quartiles, respectively; P<0.05). At the end of 20 min of hyperthermic treatment at 44 degrees C, relative tumour blood flow was reduced to 40.5% (20.7, 43.3) compared to values before treatment (median, 25% and 75% quartiles, respectively; P<0.05). Imaging of T1 relaxation times revealed a heterogeneous distribution in temperature during hyperthermic treatment.

CONCLUSION

This novel in vivo model allows standardised investigations for the development and validation of MR thermography methods.

Recombinant human growth hormone for reconditioning of respiratory muscle after lung volume reduction surgery

OBJECTIVE

To investigate the effects of recombinant human growth hormone (rHGH) as a "rescue treatment" in an end-stage chronic obstructive pulmonary disease patient after prolonged weaning failure.

DESIGN

Descriptive case report.

SETTING

Fifteen-bed intensive care unit in a university hospital.

PATIENT

A 62-year-old man with end-stage chronic obstructive pulmonary disease and pulmonary emphysema after lung reduction surgery and prolonged weaning failure after long-term mechanical ventilation.

INTERVENTIONS

After 42 days of unsuccessful weaning from the respirator, rHGH (27 IU/day, 0.3 IU/kg body weight/day) was administered for 20 days through a subcutaneous injection in addition to standard intensive care.

MEASUREMENTS AND MAIN RESULTS

In addition to daily routine laboratory studies, the visceral proteins prealbumin, retinol-binding protein, and transferrin, and nitrogen balance were measured twice a week, as were the thyroid hormones triiodothyronine, thyroxine, and thyroid-stimulating hormone, plasma insulin levels, and the insulin-like growth factor (IGF)-1 binding proteins IGF-BP1 and IGF-BP3. IGF-1 was measured from day 1 to day 4 of rHGH administration. Nutritional support was guided by indirect calorimetry. Additionally, weaning variables such as peak expiratory flow rate and expiratory tidal volume were measured noninvasively. T-piece weaning trials were carried out daily until respiratory muscle fatigue occurred. IGF-1 increased in response to rHGH stimulation, from 103 to 230 microg/mL, within 4 days. The carrier protein IGF-BP3 increased from 126 to 283 mg/L at the end of the study period, and the inhibiting IGF-BP1 decreased initially from 19 to 14 mg/L and then increased until the end of the study to 31 mg/L. Nitrogen balance increased initially from 4.6 to 13.6 g/24 hrs and thereafter decreased until the end of rHGH treatment to 8.3 g/24 hrs. Resting energy expenditure increased from 1800 to 2300 kcal/24 hrs. Peak expiratory flow rate increased from 0.69 to 0.88 L/sec. The expiratory tidal volume showed a slight increase during the study period during the daily decrease of pressure support on the ventilator setting. Respiratory muscular strength increased beginning 10 days after rHGH therapy was started. From this point, T-piece weaning trials could be prolonged almost daily. The patient was extubated successfully on postoperative day 75.

CONCLUSIONS

This case report shows that after a prolonged catabolic state and long-term mechanical ventilation, administration of rHGH not only enhances the response of protein metabolism but improves respiratory muscular strength. Therefore, it may reduce the duration of mechanical ventilation in selected patients.

Leukocyte margination in alveolar capillaries: interrelationship with functional capillary geometry and microhemodynamics

The pulmonary capillary microvasculature harbors a large pool of intravascularly marginated leukocytes. In this study, we investigated the interrelationship of leukocyte margination with characteristics of functional capillary geometry and microhemodynamics in alveolar capillary networks. In 22 anesthetized rabbits we assessed functional capillary density, average capillary length, red blood cell velocity and leukocyte kinetics in alveolar capillary networks in vivo by intravital fluorescence microscopy. In alveolar wall areas of 12,800 +/- 1,800 microm(2), we detected 3.6 +/- 0.5 sticking leukocytes and 21.0 +/- 1.9 functional capillary segments with an average capillary length of 35.7 +/- 2.1 microm. We calculated that approximately 15% of functional capillary segments are blocked by marginated leukocytes. Leukocyte margination was predominantly observed in capillary networks characterized by a high functional capillary density, short capillary segments and low red blood cell velocities. The multitude of interconnected capillary channels in these networks may allow alveolar blood flow to bypass marginated leukocytes. Hence, this interrelationship may be relevant for maintenance of adequate alveolar perfusion and low capillary network resistance despite excessive leukocyte margination in the pulmonary microvasculature. Local microhemodynamic factors may play a regulatory role in the spatial distribution of leukocyte margination.

Leukocyte sequestration in pulmonary microvessels and lung injury following systemic complement activation in rabbits

Inflammatory reactions are associated with sequestration of leukocytes in the lung. Complement activation leads to accumulation of leukocytes in alveolar septa and alveoli, to lung edema and hemorrhage. Although in organs other than the lung leukocytes interact with the vascular endothelium only in postcapillary venules, alveolar capillaries are considered to be the site of leukocyte sequestration in the lung. However, pulmonary venules and arterioles have not been investigated systematically after complement activation so far. A closed thoracic window was implanted in anesthetized rabbits; leukocytes and red blood cells were stained, and the movement of these cells was measured in superficial pulmonary arterioles, venules and alveolar capillaries using fluorescence video microscopy before and 30 and 60 min after infusion of cobra venom factor (CVF). Erythrocyte velocity and macrohemodynamic conditions did not change after CVF infusion and were not different from the sham-treated controls. The number of sticking leukocytes increased significantly compared to baseline and control: by 150% in arterioles and in venules and by 740% in alveolar capillaries within 60 min after CVF infusion. The width of alveolar septa in vivo was significantly enlarged after CVF infusion, indicating interstitial pulmonary edema. At the end of the experiments, myeloperoxidase activity was higher in the CVF group, showing leukocyte sequestration in the whole organ. It is concluded that complement activation by CVF induces leukocyte sequestration in lung arterioles, venules and alveolar capillaries and leads to mild lung injury.

Active and higher intracellular uptake of 5-aminolevulinic acid in tumors may be inhibited by glycine

Topical 5-aminolevulinic acid is used for the fluorescence-based diagnosis and photodynamic treatment of superficial precancerous and cancerous lesions of the skin. Thus, we investigated the kinetics of 5-aminolevulinic acid-induced fluorescence and the mechanisms responsible for the selective formation of porphyrins in tumors in vivo. Using amelanotic melanomas (A-Mel-3) grown in dorsal skinfold chambers of Syrian golden hamsters fluorescence kinetics were measured up to 24 h after topical application of 5-aminolevulinic acid (1%, 3%, or 10%) for 1 h, 4 h, or 8 h by intravital microscopy (n = 54). Maximal fluorescence intensity in tumors after 1 h application (3% 5-aminolevulinic acid) occurred 150 min and after 4 h application (3% 5-aminolevulinic acid) directly thereafter. Increasing either concentration of 5-aminolevulinic acid or application time did not yield a higher fluorescence intensity. The selectivity of the fluorescence in tumors decreased with increasing application time. Fluorescence spectra indicated the formation of protoporphyrin IX (3% 5-aminolevulinic acid, 4 h; n = 3). The simultaneous application of 5-aminolevulinic acid (3%, 4 h) and glycine (20 microM or 200 microM; n = 10) reduced fluorescence in tumor and surrounding host tissue significantly. In contrast, neither decreasing iron concentration by desferrioxamine (1% and 3%; n = 10) nor inducing tetrapyrrole accumulation using 1, 10-phenanthroline (7.5 mM; n = 5) increased fluorescence in tumors. The saturation and faster increase of fluorescence in the tumor together with a reduction of fluorescence by the application of glycine suggests an active and higher intracellular uptake of 5-aminolevulinic acid in tumor as compared with the surrounding tissue. Shorter application (1 h) yields a better contrast between tumor and surrounding tissue for fluorescence diagnosis. The additional topical application of modifiers of the heme biosynthesis, desferrioxamine or 1,10-phenanthroline, however, is unlikely to enhance the efficacy of topical 5-aminolevulinic acid-photodynamic therapy at least in our model.

Distribution and pharmacokinetics of Photofrin in human bile duct cancer

Prognosis of patients with bile duct tumors is mostly poor due to late diagnosis and a lack of adequate curative and palliative treatment modalities. To evaluate the potential of photodynamic therapy (PDT) as a novel and alternative treatment approach, we have investigated the uptake and tumor-specific localization of the photosensitizer Photofrin in human biliary tract neoplasms. We have quantified the distribution and the pharmacokinetics of Photofrin in normal and tumor tissue biopsies of the human bile duct by quantitative fluorescence microscopy and digital image analysis of cryosections. Fluorescence intensities (expressed as a percentage of a standard) are 19.0 +/- 11.4% and 25.2 +/- 12.7% for tumors and 10.9 +/- 2.9% and 13.2 +/- 9.1% (mean +/- SD) for normal bile duct tissue at 24 h (n = 5) and 48 h (n = 8) after Photofrin administration (2 mg kg-1 i.v.), respectively, and decrease afterwards in normal bile duct tissue over the period of investigation (4-35 days). The ratios of fluorescence in tumor versus normal tissue are found to be 1.7 +/- 0.7 and 2.3 +/- 1.2 (mean +/- SD) at days one and two after Photofrin administration, respectively. Thus, Photofrin preferentially accumulates in bile duct neoplasms, reaching peak values during the first two days. These data suggest that laser irradiation should be performed within this period after Photofrin injection to achieve tumor selectivity of PDT for effective treatment of bile duct carcinoma.

Pharmacokinetics and selectivity of aminolevulinic acid-induced porphyrin synthesis in patients with cervical intra-epithelial neoplasia

Photodynamic therapy (PDT), due to its tumor selectivity, represents an alternative approach to diagnose and treat cervical intra-epithelial neoplasia (CIN) without altering normal surrounding tissue. Our aim was to investigate the pharmacokinetics and the selectivity of 5-aminolevulinic acid (5-ALA)-induced porphyrin fluorescence after topical administration, to obtain basic clinical data for future diagnostic fluorescence imaging and PDT protocols for CIN. Twenty-eight non-pregnant women with a cytological diagnosis of low-grade or high-grade squamous intra-epithelial lesions were included. An aqueous solution containing 3% 5-ALA was topically applied 1 to 6 hrs prior to conization using a cervical cap. After excision, porphyrin-induced fluorescence was quantified in dysplastic (n = 14) and normal epithelium (n = 28) by means of quantitative fluorescence microscopy. High values of porphyrin fluorescence were found in squamous epithelium between 150 and 450 min, with a maximum at 300 min following administration of 5-ALA. Ratios of porphyrin fluorescence of dysplastic vs. surrounding normal epithelium were 1.3 and 1.21 for CIN 1 (n = 3) and CIN 2 (n = 3), respectively. In CIN 3 patients (n = 8), this ratio was 2.35; the best selectivity of 5-ALA-induced porphyrin fluorescence in CIN 3 lesions (ratio 3) was observed with a topical administration time of between 150 and 250 min. Our results demonstrate that patients with CIN 3 show higher 5-ALA-induced fluorescence compared with normal epithelium. The optimal administration time of topically applied 5-ALA was between 3 and 4 hr. Our data suggest that topical ALA-PDT and photodynamic diagnosis might be suitable for detecting CIN.

Procalcitonin as a marker of systemic inflammation after conventional or minimally invasive coronary artery bypass grafting

Cardiac surgery using cardiopulmonary bypass (CPB) often induces a systemic inflammatory response syndrome (SIRS). The concept of minimally invasive direct coronary artery bypass (MIDCAB) eliminates cardiopulmonary bypass. We evaluated the perioperative time course of procalcitonin (PCT) to compare the inflammatory response due to these two different surgical procedures. 57 patients were studied: CABG with CPB (n = 30), MIDCAB without CPB (n = 27). The following data were measured preoperatively, after induction of anesthesia, after separation from CPB in the CABG group or after left internal mammary artery (LIMA)-to-left anterior descending artery (LAD) anastomosis in MIDCAB group, and every 3 hours for the first 42 hours in the ICU: PCT, C-reactive protein (CRP), body temperature, hemodynamic parameters, and the need for catecholamines. Leucocyte counts were measured daily. For statistical analyses the Friedmann, Wilcoxon, or Mann-Whitney U tests were used. PCT in the CABG group rose to a maximum of 2.0 ng/ml (median) at 15 hrs postoperatively. In the MIDCAB group maximal PCT concentration was 0.7ng/ml (median) (p < 0.05). CRP was elevated to 17.1 mg/dl in the CABG and 18.5mg/dl in the MIDCAB group (n.s.). The leucocyte counts were increased on day 2 in the CABG group (p < 0.05). In the CABG group about 25% of the patients needed noradrenaline, but in the MIDCAB group none (p < 0.05). Body temperature did not differ between both groups. The increase in PCT concentration was more pronounced after CABG, indicating a reduced inflammatory response after MIDCAB. CRP was increased after both procedures. PCT reflects the inflammatory response after cardiac bypass surgery with or without CPB.

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.

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.

Intraoperative detection of malignant gliomas by 5-aminolevulinic acid-induced porphyrin fluorescence

OBJECTIVE

Survival after surgery and radiotherapy for the treatment of malignant gliomas is linked to the completeness of tumor removal. Therefore, methods that permit intraoperative identification of residual tumor tissue may be of benefit. In a preliminary investigation, we have studied the value of fluorescent porphyrins that accumulate in malignant tissue after administration of a precursor (5-aminolevulinic acid) for labeling of malignant gliomas in nine patients.

METHODS

Three hours before the induction of anesthesia, 10 mg 5-aminolevulinic acid/kg body weight was administered orally. Intraoperatively, red porphyrin fluorescence was observed with a 455-nm long-pass filter after excitation with violet-blue (375-440 nm) xenon light and was verified by analysis of fluorescence spectra. Fluorescing and nonfluorescing samples taken from the tumor perimeters were examined histologically or used to study the photobleaching of porphyrins by excitation light and white light from the operating microscope. Plasma and erythrocyte porphyrin levels were determined by fluorescence photometry.

RESULTS

Normal brain tissue revealed no porphyrin fluorescence, whereas tumor tissue was distinguished by bright red fluorescence. For a total of 89 tissue biopsies, sensitivity was 85% and specificity was 100% for the detection of malignant tissue. For seven of nine patients, visible porphyrin fluorescence led to further resection of the tumor. Under operating light conditions, fluorescence decayed to 36% in 25 minutes for violet-blue light and in 87 minutes for white light. Plasma and erythrocyte porphyrin contents increased slightly, without exceeding normal levels.

CONCLUSION

Our observations suggest that 5-aminolevulinic acid-induced porphyrin fluorescence may label malignant gliomas safely and accurately enough to enhance the completeness of tumor removal.

Indocyanine green and laser light for the treatment of AIDS-associated cutaneous Kaposi's sarcoma

Indocyanine green (ICG) is clinically approved for the determination of liver function, cardiac output and plasma volume. In this pilot study, ICG was used as photosensitizer in combination with a diode laser to treat AIDS-associated Kaposi's sarcoma (KS) in three patients. Directly and up to 50 min after intravenous administration of ICG (2-4 mg kg(-1) body weight), KS (n=57), mainly plaque-type, were irradiated using a diode laser (lambda em=805 nm, 100 J cm[-2], 0.5-5 W cm[-2]) matching the absorption maximum. Complete remission of KS (n=16) was achieved when irradiated 1-30 min after injection of the second dose of ICG (2 x 2 mg kg(-1) b.w., 30 min apart) with 3-5 W cm(-2) and 100 J cm(-2). Biopsies (n=3) revealed necrosis of the tumour 24 h and complete remission 4 weeks after therapy. In general, systemic side-effects were not observed and cosmetic results were very good. However, hyperpigmentation occurred temporarily in lesions located on the lower extremities. These findings show that AIDS-associated KS can be effectively treated after photosensitization with ICG and subsequent irradiation with an appropriate diode laser. However, additional investigations need to elucidate the exact mechanism of action of ICG-mediated phototherapy and have to show the efficacy for the treatment of other highly vascularized solid tumours.

[Effect of humanised anti-L- selectin antibody HuDreg 200 on leukocyte kinetics in pulmonary microcirculation in endotoxinemia]

In the pulmonary circulation, endotoxemia induces leukocyte/endothelium interaction in pulmonary arterioles and venules. Thus, leukocytes may contribute to the pathogenesis of acute lung injury. In order to investigate, whether this interaction can be inhibited by early blockade of the adhesion cascade, we studied the effect of the humanized anti-L-selectin antibody HuDreg 200 on leukocyte kinetics in pulmonary arterioles and venules following i.v.-infusion of endotoxin. In endotoxemia HuDreg 200 reduces sticking of leukocytes in both pulmonary arterioles and venules. Thus, we were able to demonstrate that early blockade of the adhesion cascade effectively prevents leukocyte accumulation in pulmonary microvessels in endotoxemia. Therefore, HuDreg 200 may exhibit protective effects on the manifestation of leukocyte-mediated acute lung injury.

Targeting of the tumor microcirculation by photodynamic therapy with a synthetic porphycene

9-acetoxy-2,7,12,17-tetrakis-(beta-methoxyethyl)-porphycene (ATMPn) is a chemically pure substance with fast pharmacokinetics and superior photodynamic properties in vitro as compared to Photofrin. In this study the pharmacokinetics, photodynamic efficacy and tissue localization of ATMPn were investigated in vivo. Amelanotic melanomas (A-Mel-3) were implanted in dorsal skin fold chambers fitted to Syrian Golden hamsters. Fluorescence kinetics of ATMPn (1.4 mumol kg-1 b.w.i.v.; n = 8) were monitored by intravital microscopy. Quantitative measurements of fluorescence intensity were carried out by digital image analysis. For tumor growth studies 1.4 mumol kg-1 was injected 24 h (n = 3), 3 h (n = 3), 1 min (n = 6) and 2.8 mumol kg-1 1 min (n = 6) before PDT (Laser (630 nm) or lamp (600-750 nm), 100 mW cm-2, 100 J cm-2). Tumor volume was measured for 28 d. Solid tumors (n = 3) were excised 1 min after injection of ATMPn (2.8 mumol kg-1) and cryostat sections (20 mm) were analyzed by confocal laser scanning microscopy (CLSM) for tissue localization of the dye. Maximal fluorescence (mean +/- S.E.) arose in the tumor (94 +/- 7%) and surrounding host tissue (67 +/- 5%) 30 s post injection followed by a rapid decrease. Hardly any fluorescence was detectable 12 h after administration. Only PDT 1 min after injection of ATMPn was effective yielding 3/6 complete remissions (2.8 mmol kg-1, laser) and 6/6 complete remissions (2.8 mumol kg-1, lamp), respectively. One minute after injection the dye is primarily localized in the vascular wall of normal and tumor vessels as shown by CLSM. PDT at a time, when the dye is localized primarily in the tumor microcirculation, exhibits the best tumor killing effects showing that vascular targeting is effective in treating solid malignant tumors. ATMPn in liposomes makes administration and light irradiation in one session possible due to its fast pharmacokinetics. Thus, using ATMPn as a photosensitizer may provide more flexibility to perform PDT after surgical exploration and debulking as adjuvant therapy.

Endovascular catheter-delivered photodynamic therapy in an experimental response to injury model

BACKGROUND

The effectiveness of local endovascular photodynamic therapy (PDT) in preventing tissue hyperplasia was evaluated in a vascular injury model.

METHODS

Standardized unidirectional arterial injury with a directional atherectomy catheter was performed in porcine arteries (n = 180). Animals (n = 72) were randomly allocated to unidirectional injury only (Group 1), injury followed by drug delivery of photosensitizer with a porous balloon (Group 2), or by local exposure to monochromatic light (Group 3). In Group 4, injury was followed by local drug delivery of photosensitizer and subsequent exposure to light (PDT). Up to 21 days after treatment, all experimental vessels were excised, fixed and processed for histology, immunohistochemistry and transmission electron microscopy.

RESULTS

After vascular injury an inflammatory and myoproliferative response was observed in Groups 1, 2 and 3 (mean tissue hyperplasia/media ratio 1.0 +/- 0.5 at 21 days; area tissue hyperplasia: 1.57 +/- 0.9 mm2). Proliferation in injured vascular segments (Group 1-3) reached a maximum at 7 days, with 6%. Only in Group 4, after injury followed by photodynamic therapy, was there no significant vascular response (mean tissue hyperplasia/media ratio 0.3 +/- 0.2: area tissue hyperplasia: 0.1 +/- 0.05 mm2 p < 0.001, proliferating cells 0.3%).

CONCLUSION

Vascular response after unidirectional injury was suppressed only by endovascular photodynamic therapy.

Photodynamic therapy with 5-aminolaevulinic acid-induced porphyrins of an amelanotic melanoma in vivo

Of particular interest for photodynamic therapy (PDT) are the endogenously formed and photodynamically active porphyrins produced following topical or systemic application of 65-aminolaevulinic acid (ALA), a haem precursor. Having determined the pharmacokinetics and wavelength dependence of PDT with ALA-induced porphyrins, we analysed the porphyrin metabolites in tumour and surrounding skin. The therapeutic efficacy of PDT using ALA-induced porphyrins was investigated. Amelanotic melanomas (A-Mel-3) were implanted subcutaneously in the back of Syrian golden hamsters (body weight (b.w.), 70-80 g). After 5-7 days, tumours with a volume of approximately 150 mm3 were used for PDT (n = 36). ALA (500 mg kg-1 b.w., pH 6.5) was injected intravenously 45, 90, 150 and 300 min before light irradiation (635 nm, 100 mW cm-2, 100 J cm-2). Tumours with light irradiation only served as controls. The tumour volume was measured after PDT for 28 days. The total porphyrin content was determined in the tumours, the surrounding skin and erythrocytes prior to and 45, 90, 180, 240, 300 and 480 min and 24 h following intravenous injection of ALA (500 mg kg-1 b.w.; n = 32). Porphyrin metabolites were separated by high pressure liquid chromatography (HPLC). Tumour growth was significantly delayed when PDT with ALA was performed 45, 90 or 150 min following intravenous administration. At that time, protoporphyrin (1.8 +/- 0.4 nmol g-1), coproporphyrin (2.2 +/- 0.5 nmol g-1) and uroporphyrin (1.7 +/- 1.4 nmol g-1) were the main metabolites in the tumour tissue. Erythrocytes also contained significant amounts of porphyrins (11.8 +/- 1.3 nmol g-1). The tumour and surrounding skin exhibited a different pattern of porphyrin metabolites. Unexpectedly, a single treatment of PDT with ALA-induced porphyrin resulted in only one complete remission out of six amelanotic melanomas when the final therapeutic outcome was assessed after 28 days. The therapeutic efficacy of PDT with ALA-induced porphyrins can be positively correlated with the fluorescence kinetics previously determined. The analysis of the porphyrin metabolites in amelanotic melanoma by HPLC indicates that the porphyrin accumulation is not due to a decreased activity of ferrochelatase. Moreover, the photodynamic effects may not be mediated solely by porphyrins localized in the tumour parenchyma, but also by significant amounts of porphyrins in the microvasculature. PDT with this endogenous photosensitizer failed to induce complete emission of the treated tumours despite irradiation at the time of maximum porphyrin concentration using the optimum therapeutic wavelength. Thus PDT with ALA-induced porphyrins is less effective in our model relative to that observed for the exogenous photosensitizer Photofrin or synthetic porphycenes after a single treatment.

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.

Indocyanine green: intracellular uptake and phototherapeutic effects in vitro

Indocyanine green (ICG; absorption peak in human plasma 805 nm) was investigated for ICG-mediated phototherapy in vitro. The cellular uptake of ICG (1 microM-50 microM) into HaCaT keratinocytes after an incubation period of 24 h increased up to an intracellular ICG concentration of 12.1 +/- 1.3 nmol per 10(6) cells. To examine dose dependent phototoxic effects in vitro, keratinocytes were incubated with 0 microM-50 microM ICG for 24 h and irradiated by a diode laser (805 nm) with different energy densities (0, 12, 24, 48 J cm-2). All applied ICG concentrations except for 5 microM yielded a cell killing effect in combination with irradiation depending significantly on ICG concentration and light dose. Cell viability for dark control and cells incubated with 50 microM ICG and irradiated with 48 J cm-2 was 0.82 +/- 0.15 and 0.07 +/- 0.02, respectively. Sodium azide (100 mM), a quencher of reactive oxygen species, inhibited significantly the cell killing using 50 microM ICG and 24 J cm-2. Taken together, photoactivation of ICG by irradiation with a diode laser was shown to induce effectively cell killing of HaCaT keratinocytes. Moreover, this effect was inhibited by sodium azide, thus irradiation of ICG might induce a photodynamic reaction.

Changes in subcutaneous interstitial fluid pressure, tissue oxygenation, and skin red cell flux during venous congestion plethysmography in men

OBJECTIVE

Venous congestion plethysmography enables noninvasive assessment of microvascular filtration capacity (Kf) in limbs. However, increases in fluid filtration might alter the balance of Starling forces: for example, progressive increases in interstitial fluid pressure (Pi) would reduce net fluid flux, thus underestimating Kf. Furthermore, elevation of cuff pressure to values close to diastolic blood pressure, as used in the protocol, may be itself impair tissue perfusion with unknown effects on the microvascular parameters investigated.

METHODS

Pi was measured in healthy volunteers (n = 14) with a modified "Wick in needle" technique during small (8 mm Hg) cumulative increases in venous pressure (0-95 mm Hg). Changes in the hemoglobin (Hb) concentration, oxygenated hemoglobin (HbO2) concentration and oxidized cytochrome aa3 concentration were assessed in the calf using noninvasive near-infrared spectroscopy. Skin red blood cell flux close to the strain gauge was evaluated by laser Doppler fluxmetry.

RESULTS

Pi at control was -0.89 +/- 0.8 mm Hg and during elevation of venous pressure remained constant until a cuff pressure of 30 mm Hg was reached. It rose thereafter to 1.57 +/- 1.3 mm Hg (mean +/- SD). Skin red cell flux was significantly reduced when cuff pressure exceeded 30 mm Hg and following cuff deflation, evidence of reactive hyperemia was obtained. Hb concentration increased significantly as a result of venous pressure elevation. No change in either HbO2 or cytochrome aa3 concentration was observed as long as cuff pressure remained under diastolic blood pressure.

CONCLUSIONS

The small increase in Pi together with an absence of impaired tissue oxygenation during the venous congestion plethysmography protocol described by Gamble et al. supports the contention that this protocol enables accurate assessment of filtration capacity.

Topical application of a first porphycene dye for photodynamic therapy--penetration studies in human perilesional skin and basal cell carcinoma

Photodynamic therapy (PDT) in dermatology has been proven to be a successful noninvasive therapeutic modality for treating skin cancer. To facilitate its clinical introduction, the development of topical photosensitizers is necessary to avoid generalized, cutaneous photosensitivity. Therefore the penetration of synthetic chemically pure 9-acetoxy-2,7,12,17-tetrakis-(beta-methoxyethyl)-porphycene (ATMPn) into human skin was studied. Single specimens of freshly excised perilesional skin (n = 70) and basal cell carcinomas (n = 28) were evaluated after topical application of ethanolic ATMPn solutions (0.1% and 0.05%) for various times (2, 6, 16, 20 h). The penetration depth of ATMPn, recognized as red fluorescence in cryostat sections, was determined qualitatively by fluorescence imaging using a system of scoring related to the morphological structure of human skin (0 no fluorescence, 5 fluorescence deeper than basement membrane). Perilesional skin incubated for 2 or 6 h revealed fluorescence restricted to the upper parts of the epidermis, while after 16 or 20 h of incubation fluorescence was detected down to the basement membrane resulting in a significantly higher score (mean sum of scores : 2 h 2.6 +/- 0.4; 6 h 3.2 +/- 0.1; 16 h 3.8 +/- 0.1; 20 h 3.6 +/- 0.1). Quantitative evaluation by digital image analysis confirmed the qualitative results. Fluorescence was limited to the epidermis and the fluorescence intensity of the epidermis was higher after 16 h (4.9% of the fluorescence standard) than after 6 h (4.1%) incubation. Basal cell carcinomas showed fluorescence in the deep dermis as early as after 6 h incubation, but restricted to tumour cell nests. These results suggest that penetration of ATMPn into tumour tissue after topical application might be sufficient for topical PDT and that poor penetration into surrounding tissue might prevent scar formation following irradiation for PDT. The penetration characteristics of ATMPn now have to be proven in an in vivo setting.

Porphyrins preferentially accumulate in a melanoma following intravenous injection of 5-aminolevulinic acid

Systemically, as opposed to topically, administered 5-aminolevulinic acid (ALA) is of increasing interest for photodynamic therapy (PDT) because of more selective and more homogeneous accumulation of porphyrins in neoplastic tissues. This study investigates the profile and the time course of porphyrin metabolites in various tissues following intravenous injection of ALA (0.5 g/kg body weight) into hamsters bearing an amelanotic melanoma (A-Mel-3). ALA injection led to maximum levels of ALA and porphyrins in erythrocytes after 45 min. In tissues, maximum porphyrin levels were detected after 45 min (tumor), 4 h (skin, kidney), and 24 h (liver). Sixfold higher porphyrin levels were observed in tumors as compared to surrounding normal skin at 45 min. Predominant porphyrin metabolites were protoporphyrin (tumor, skin, liver, kidney), coproporphyrin (tumor) and highly carboxylated porphyrins (tumor, skin, kidney). These data suggest optimum efficacy of light irradiation in systemic PDT with ALA within the first two hours after injection. Tumor-specific ALA metabolism yields protoporphyrin and coproporphyrin as the prevailing porphyrin metabolites.

Local photodynamic therapy reduces tissue hyperplasia in an experimental restenosis model

Local photodynamic therapy may have potential in preventing myointimal hyperplasia after angioplasty. In this study, the effect of photodynamic therapy was evaluated in an experimental model of restenosis. Standardized unidirectional arterial injury with a directional atherectomy catheter was performed in porcine arteries. Animals were randomly allocated to four groups: group 1, unidirectional injury only; group 2, injury followed by local delivery of photosensitizer; group 3, injury followed by local exposure to monochromatic light; and group 4, where injury was followed by local drug delivery of photosensitizer and subsequent exposure to light (photodynamic therapy). Seven, 14 or 21 days after treatment, all experimental vessels were excised, fixed and processed for histology. An inflammatory and myoproliferative response was observed after injury in vessels from groups 1, 2 and 3. In group 4, after injury followed by photodynamic therapy, the myoproliferative response was significantly reduced. Thus, in this study, tissue hyperplasia after unidirectional injury was effectively suppressed by photodynamic therapy.

Strong and prolonged induction of c-jun and c-fos proto-oncogenes by photodynamic therapy

Photodynamic therapy (PDT) is currently under investigation in phase II and III clinical studies for the treatment of tumours in superficial localisations. Thus far, the underlying mechanisms of PDT regarding cellular responses and gene regulation are poorly understood. Photochemically generated singlet oxygen (1O2) is mainly responsible for cytotoxicity induced by PDT. If targeted cells are not disintegrated, photo-oxidative stress leads to transcription and translation of various stress response and cytokine genes. Tumour necrosis factor (TNF) alpha, interleukin (IL) 1 and IL-6 are strongly induced by photodynamic treatment, supporting inflammatory action and immunological anti-tumour responses. To investigate the first steps of gene activation, this study focused on the proto-oncogenes c-jun and c-fos, both coding for the transcription factor activator protein 1 (AP-1), which was found to mediate IL-6 gene expression. We here determine the effects of photodynamic treatment on transcriptional regulation and DNA binding of transcription factor AP-1 in order to understand the modulation of subsequent regulatory steps. Photodynamic treatment of epithelial HeLa cells was performed by incubation with Photofrin and illumination with 630 nm laser light in vitro. Expression of the c-jun and c-fos genes was determined by way of Northern blot analysis, and DNA-binding activity of the transcription factor AP-1 was evaluated by electrophoretic mobility shift assay (EMSA). Photofrin-mediated photosensitisation of HeLa cells resulted in a rapid and dose-dependent induction of both genes but preferential expression of c-jun. Compared with the transient expression of c-jun and c-fos by phorbol ester stimulation, photodynamic treatment led to a prolonged activation pattern of both immediate early genes. Furthermore, mRNA stability studies revealed an increased half-life of c-jun and c-fos transcripts resulting from photosensitisation. Although mRNA accumulation after PDT was stronger and more prolonged compared with phorbol ester stimulation, with regard to AP-1 DNA-binding activity, phorbol ester was more efficient. Surprisingly, in addition to the activation of AP-1 DNA-binding via PDT, photodynamic treatment can decrease AP-1 DNA-binding of other strong inducers, such as the protein kinase C-mediated pathway of phorbol esters and the antioxidant pyrrolidine dithiocarbamate (PDTC). This study demonstrates a strong induction of c-jun and c-fos expression by PDT, with prolonged kinetics and mRNA stabilisation as compared with activation by phorbol esters. Interestingly, this observation is not coincident with an overinduction of AP-1 DNA-binding, hence suggesting that post-translational modifications are dominant regulatory mechanisms after PDT that tightly control AP-1 activity in the nucleus thus limiting the risk of deregulated oncogene expression.

Measurement of neutrophil content in brain and lung tissue by a modified myeloperoxidase assay

Myeloperoxidase (MPO) activity is assessed for the quantification of neutrophil accumulation in tissues. In particular, it may be used to support in vivo data on leukocyte kinetics obtained by intravital microscopy and to clarify whether phenomena observed on the organ surface reflect the situation of the whole organ microcirculation. Previous measurements of MPO activity were limited by interference with other peroxidases and by inhibition of MPO activity by specific enzymes. To circumvent these limitations, a modified assay was devised that combined a two-step tissue homogenization technique with heat incubation in a continuous photometric measurement. MPO activity was quantified in neutrophils isolated from rat and rabbit whole blood, rat brain and rabbit lung and compared with intravital microscopic data on leukocyte accumulation. The modified assay is characterized by high reproducibility, strong correlation of MPO activity with number of neutrophils and full recovery of neutrophils added to tissue homogenate. MPO activity per neutrophil was 342.9 +/- 11.7 mU/10(6) cells in rats and 40.3 +/- 0.8 mU/10(6) cells in rabbits. MPO activity in tissue was significantly lower in rat brains (18.9 +/- 29.7 mU/g) as compared to rabbit lungs (741 +/- 67 mU/g). Whereas global cerebral ischemia/reperfusion did not increase MPO activity in rat brain (18.1 +/- 26.1 mU/g), intravenous infusion of cobra venom factor (1,447 +/- 407 mU/g) or endotoxin (1,439 +/- 285 mU/g), enhanced MPO activity in rabbit lung. These results parallel microcirculatory data from the organ surface. Therefore they supplement the intravital microscopic observations by demonstrating that these are indeed representative of deeper parenchymal tissue areas.

Photodynamic eradication of amelanotic melanoma of the hamster with fast acting photosensitizers

Three porphycenes with fast pharmacokinetics were tested for their ability to photosensitize amelanotic hamster melanoma A-Mel-3 at short time intervals after injection. Laser light irradiation was performed at the time of maximal photosensitizer level in tumor tissue. Photodynamic therapy as short as 5 min after injection led to complete local tumor remission at a dosage of 1.4 mumol/kg for the porphycene CBPn. In comparison, Photofrin required 8.4 mumol/kg for local tumor remission in 5 of 6 animals with 24 hr accumulation time after injection. We propose a swift photodynamic protocol which can compete favorably with conventional techniques of tumor treatment.

Comparison of local intravascular drug-delivery catheter systems

Systemic and local delivery of the photosensitive drug Photofrin polyporphyrin was investigated in normal porcine arteries (n = 192). A macroporous balloon and a novel needle injection catheter were used for local drug delivery and compared with systemic delivery. Fluorescence microscopy combined with digital image analysis was used to quantify the drug-related fluorescence. Systemic delivery showed a maximum in the intima at 4 hours. Application with the porous balloon revealed maximum indicator-related fluorescence intensity in the intima after 5 minutes; delivery with the needle injection catheter resulted in a several-fold enhanced maximum in adventitia after 30 minutes compared with the maximum achieved with either systemic injection or porous balloon application. After 21 days fluorescence was detectable in arteries treated with the new needle injection catheter. Local drug delivery is feasible with either system, but prolonged delivery was achieved only with the needle injection catheter.

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.

Wavelength dependency of photodynamic effects after sensitization with 5-aminolevulinic acid in vitro and in vivo

A promising new therapeutic modality for skin cancer, administration of the heme precursor 5-aminolevulinic acid followed by light irradiation, is known as photodynamic therapy. Photofrin, the only clinically approved sensitizer, has an absorption maximum at 630 nm, the wavelength used in most experimental and clinical trials with 5-aminolevulinic acid. We investigated photodynamic efficacy of irradiation with coherent light at wavelengths ranging from 622 to 649 nm in vitro and in vivo as well as the content and distribution of intracellular porphyrin after administration of 5-aminolevulinic acid. HaCaT immortalized human keratinocytes were sensitized with 30 micrograms/ml 5-aminolevulinic acid for 24 h in vitro. By cell viability determined with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, the best cell-killing effects were observed after irradiation at 635 nm. Using an amelanotic melanoma (A-Mel-3) grown subcutaneously in Syrian Golden hamsters, we confirmed these results in vivo: tumor growth was markedly delayed in animals treated with 100 mg/kg 5-aminolevulinic acid intravenously and irradiated with coherent light at 635 nm as compared to animals irradiated at 630 nm. This photodynamic effect is probably mediated by large amounts of the photosensitizing porphyrin, protoporphyrin IX, localized in cell membranes as visualized by confocal laser scan microscopy and as determined by high pressure liquid chromatography in vitro. The results suggest that irradiation at 635 nm with a coherent light source is more effective than irradiation at 630 nm for photodynamic therapy with 5-aminolevulinic acid.

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.

[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.

A new catheter for prolonged local drug application

BACKGROUND

Local drug delivery using a new 5F catheter with six small needles is described. The needles can be extended laterally into vascular tissue for drug deposition.

METHODS

A fluorescent indicator (Photofrin) was injected with a new local drug delivery device into porcine carotid arteries. The vessels were explanted 15, 30, 60 min and 14 days after local drug delivery. Vascular segments were analyzed using semi-quantitative measurement of fluorescence (calculated in relation to a standard, 100% representing the maximum fluorescence achieved by systemic intravenous application of Photofrin).

RESULTS

Maximum fluorescence was found in adventitia (15 min: 374%; 30 min: 388%; 60 min: 251%). In intimal tissue, the detected fluorescence was 107% after 15 min, 294% after 30 min, and 25% after 60 min. Media fluorescence was lower (15 min: 151%, 30 min: 102%, 60 min: 55%). No systemic drug content was measured. Fourteen days after local drug delivery, 15% of maximal fluorescence was still found in media but no adverse tissue hyperplasia was observed.

CONCLUSIONS

These experiments demonstrate that high-dose perivascular local drug delivery is feasible and allows prolonged and selective application of drugs in a vessel segment without side effects.

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.

[Use of photodynamic laser therapy in gynecology]

OBJECTIVE

Dysplasia of the vulva and uterine cervix are often multicentric, tend to recur and have mostly to be treated by surgical procedures. The photodynamic laser therapy (PDT) may be an alternative, which selectively destroys neoplastic tissue after topical delta-aminolevulinic acid (ALA) used as a photosensitizer.

METHODS

We measured the distribution of fluorescence in dysplastic and nondysplastic tissue after topical application of ALA in 27 patients with dysplasia. In 3 vulvar and 2 cervical dysplasias, PDT was performed.

RESULTS

We could show a selective enrichment of endogenous porphyrins in dysplastic tissues, whereas benign tissue showed no fluorescence. The fluorescence was limited to the mucosa. The heterogeneous fluorescence pattern was influenced by the duration of ALA application. In the treated patients, cytological and clinical parameters showed improvement after use of PDT. The longest recurrence-free interval from treatment up to date is 15 months (range 3-15 months).

CONCLUSIONS

After first results of penetration studies and clinical follow-up, PDT after topical ALA application seems to be a good alternative to surgical procedures in dysplastic changes of the genital tract.

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.

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.

Photodynamic antitumor agents: beta-methoxyethyl groups give access to functionalized porphycenes and enhance cellular uptake and activity

Porphycene photosensitizers bearing two or four methoxyethyl side chains were synthesized in nine steps from commercially available starting materials. Ether cleavage led to (hydroxyethyl)- and (bromoethyl)porphycenes that were converted to vinyl and benzo derivatives. Five of the side chain-functionalized porphycenes were biologically studied in comparison with two tetra-n-propylporphycenes. Porphycenes were incorporated in small unilamellar liposomes and incubated with cultivated SSK2 murine fibrosarcoma cells. Cellular uptake and phototoxicity 24 h after 5 J/cm2 laser light treatment were determined. The porphycenes tested were between 17 and 220 times more photodynamically active than the currently clinically used sensitizer Photofrin, although extinction coefficients of the porphycenes' irradiated bands are only approximately 10-fold higher. The LD50 concentration for SSK2 cells in the incubation medium was as low as (8.5 +/- 2.8) x 10(-9) M for tetrakis(methoxyethyl)porphycene. Two methoxy or hydroxy groups enhanced cellular uptake, three or four methoxy groups both enhanced and accelerated cellular uptake of tetraalkylporphycenes. Half-life times of the uptake processes varied between (0.14 +/- 0.04) and (14 +/- 4) h and cellular saturation levels between (1.2 +/- 0.2) and (26 +/- 3) pmol/10(5) cells. When individual uptake rates were accounted for, all porphycenes had a similar "cellular" phototoxicity, pointing toward a common mechanism of action. Evidence is presented for the assumption that cell membranes are the primary targets of the tested porphycenes and that membrane solubility may play a critical role in their photodynamic efficiency. The results show that nonionic polar side chain functionalities can strongly enhance cellular uptake and antitumor activity of lipophilic porphyrinoids and thus that the known lipophilicity/activity relationship can be reversed for very hydrophobic sensitizers.

[Endoscopic, 3-dimensional measurement of neoplasms and stenoses of the larynx and trachea]

Calculating the exact measures of laryngeal tumours will be crucial for the next generation of the TNM System. Furthermore, cross-sectional area and length of a laryngotracheal stenosis are of major interest for clinical management. It is the aim of this study to assess these parameters endoscopically in a more detailed and exact manner. For this purpose a Hopkins Endoscope (Karl Storz, Tuttlingen, Germany) and a slide caliper are combined. This new instrument is called laryngometer (Fig. 1a u. b). It helps to measure the lengths of a stenosis or neoplasm. In addition it defines the level of a given object and provides a standard in a two-dimensional video sequence. Thus the laryngometer allows to digitally analyse cross-sectional areas and distances as well as to evaluate craniocaudal parameters.

Evaluation of photodynamic therapy-induced heating of hamster melanoma and its effect on local tumour eradication

To investigate the contribution of hyperthermia on local tumour eradication by photodynamic therapy (PDT) we quantified PDT induced tumour heating and evaluated its biological effect in vivo. Syrian Golden hamsters bearing an amelanotic melanoma implanted into the dorsal skin received intravenous injections of Photofrin (5 mg kg-1). Twenty-four hours later tumours were illuminated by red light (630 nm; total energy: 100 J cm-2) at 100 and 200 mW cm-2 and tumour surface and tumour centre temperature were measured. The tumoricidally threshold temperature of 43 degrees C was exceeded at 200 mW cm-2 only, revealing a calculated equivalent treatment time at 43 degrees C of about 10 min. Melanomas treated by PDT at both light intensities disappeared within 48 h and did not reappear locally within the observation period of 32 days. Tumours treated by hyperthermia (water bath) at the maximum temperatures measured during illumination at 200 mW cm-2 (45.5 degrees C for 500 s) or animals receiving laser light at 200 mW cm-2 alone showed a significant growth delay compared to controls (p < 0.05), whereas illumination at 100 mW cm-2 alone or hyperthermia corresponding to the maximum temperature obtained at 100 mW cm-2 (39.5 degrees C for 1000 s) did not alter tumour growth. These data indicate that tumour temperature increased during PDT and exceeded the hyperthermic threshold temperature of 43 degrees C at 200 mW cm-2. In our tumour model hyperthermia was not necessary for a complete tumour eradication by PDT. Although a combination of PDT and hyperthermia might act in an additive or synergistic manner, an unrecognized overlap of both effects might complicate the interpretation of studies on the mechanisms of PDT.

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.

Photodynamic therapy-induced alterations in interstitial fluid pressure, volume and water content of an amelanotic melanoma in the hamster

The effect of photodynamic therapy (PDT) on interstitial fluid pressure (IFP), tumour volume and water content was measured in melanomas grown in hamsters. Unlike control tumours, treated tumours exhibited a 40-60% increase in volume at 1, 3 and 6 h post PDT. IFP also increased at 1 and 3 h after PDT, but decreased to 50% of control value after 24 h, presumably as a result of PDT-induced microcirculatory impairment.

Relation of early Photofrin uptake to photodynamically induced phototoxicity and changes of cell volume in different cell lines

For efficacy of photodynamic therapy, selective uptake and retention of photoactive substances has been postulated. Therefore, measurements were performed to find out whether the photosensitiser Photofrin is taken up differently in malignant and non-malignant cells in vitro. In addition, the sensitivity of malignant cells and non-malignant cells to photodynamic exposure was investigated, by quantifying viability and volume alterations of the cells. Bovine aortic endothelial cells, mouse fibroblasts and amelanotic hamster melanoma cells were suspended in a specially designed incubation chamber under controlled conditions (e.g. pH, pO2, pCO2 and temperature). After establishing constant baseline conditions, the cellular fluorescence intensity per cell volume, indicative of the uptake of Photofrin, and cell volume were assessed by flow cytometry, and cell viability was quantified by the trypan blue exclusion test. Photodynamic exposure of cells was performed using an argon-pumped dye laser system via a 600 microns optical fibre at energy density of 4 Joules at the cell surface (40 mW/cm2, 100 s). In comparison to endothelial and fibroblast cells, the melanoma cells exhibited no increased uptake of Photofrin, and no enhanced sensitivity to photodynamic therapy (PDT). However, the fluorescence intensity/volume of endothelial cells was two to three times higher at each concentration of the photosensitiser. Following PDT, reduction in cell viability was dependent on the concentration of Photofrin, and directly correlated with fluorescence intensity per cell volume. In addition, the cells of all three lines, treated by PDT, revealed dose-dependent changes in cell volume. Melanoma cells exhibited the most excessive increase. It is suggested that selective uptake of photosensitiser in vitro is not characteristic for tumour cells. The high uptake of Photofrin by endothelial cells may indicate that the vascular endothelium is a major target for PDT, leading to cessation of tumour blood flow and subsequent destruction of tumour tissue. In addition, PDT-induced swelling of tumour cells might represent and effect synergistically impairing tumour perfusion, and thereby promoting tumour death.

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.

An in vitro model to study cellular photosensitizer uptake and photodynamic dose-response relationships of tumor cells

Cellular fluorescence intensity (CFI) after incubation with varying concentrations of the photosensitizer Photofrin and the photodynamically induced dose-response relationships of hamster melanoma cells (A-MEL-3) were studied in a recently developed in vitro model. After administration of Photofrin to the extracellular serum-free medium, CFI was evaluated by flow cytometry together with constantly fluorescing latex particles used as a reference. After 5 min, 50% of maximal CFI was found, and after 60 min CFI was maximal. No further increase was obtained during the exposure to Photofrin over the incubation period of 4 h. During this plateau phase, CFI was significantly related to the concentration of Photofrin in the extracellular medium (r = 0.94; P < 0.001). Subsequent to increasing intervals of Photofrin exposure, cells were irradiated with laser light at 630 nm (40 mW/cm2, 4J). Cell viability as evaluated by trypan blue exclusion was significantly decreased with increasing concentrations of Photofrin in the medium, and significantly correlated with CFI during the plateau phase. After photodynamic treatment (PDT) cell fluorescence was reduced by about 15%. This was neither dose- nor time-dependent. On the basis of these findings we propose that CFI indicates photosensitizer uptake. This is also supported by the relation between CFI and phototoxicity. The latter also suggests that CFI might be useful to predict the PDT in vivo efficacy by this in vitro model. Besides measurements of photosensitizer uptake and cell photoxicity, the model demonstrates an excellent opportunity to study the molecular mechanisms of action associated with PDT.