Visible detection of early stage cancer labelled with the fluorescing porphyrin mixture of dihematoporphyrin‐ether and dihematoporphyrin‐ester (DHE) is often limited by a high and inhomogeneously distributed level of autofluorescence. A new imaging method for reducing autofluo‐rescence is described. The method uses alternating fluorescence excitation with laser light in the violet and blue spectral ranges. Subtraction of the corresponding fluorescence images results in contrast enhancement due to an effective reduction in the autofluorescence contribution. A prototype version of a highly sensitive fluorescence imaging device including a modified krypton ion laser, an image‐intensified solid‐state TV‐camera, a digital image‐processing system, and video recording and monitoring has been developed.
Experiments performed with this fluorescence imaging system on a tumorous dog bladder showed that a dose of 0.2 mg DHE kg−1 body wt, which is far below the dose administered for photodynamic therapy (2‐5 mg kg−’body wt), is sufficient to give a high‐contrast fluorescence image. The corresponding excitation power density was about 1 W m−2. Photobleaching of DHE was observed during fluorescence detection at excitation power densities exceeding 1 kW m−2. At these high excitation levels DHE fades out nearly completely within 0.25 min.
To compare the effects of laser light with those of radiofrequency (RF) current on ventricular myocardium, a total of 36 lesions (endocardial approach n = 10 each and epicardial approach n = 8 each) were produced by either transcatheter laser (Nd:YAG, 1,064 nm, 30 W, 30 s) or RF (70 °C, 30 s) catheter applications in the beating hearts of 4 dogs. Volumes of coagulated myocardium in endo-/epicardial approaches were 996 ± 73/1,075 ± 82 (laser) and 111 ± 38/44 ± 5 mm3 (RF). RF lesions showed intramural bleeding, rupture and dissociation of myocardial fibers, tissue vaporization with crater and thrombus formation. Transcatheter application of laser light produced significantly larger and better reproducible lesions than RF current, without undesirable effects on the ventricular walls.
Eight beagle dogs were exposed for 290 d to a low concentration of sulfur(/\/) aerosol 10.3 mg m -3 S(IQ corresponding to 0.6 mg m -3 sulfur dioxide]. No clinical symptoms were found that could be correlated with the pollutant. However, significant changes were observed in some of the biochemical and cellular parameters determined in sequential bronchoalveolar lavage (EAL) fluids. The protein and albumin concentration increased (p < .05) in the second half of the exposure period, indicating changes in the transudation kinetics of serum proteins into the alveolar lumen. The relative levels of methionine sulfoxide and carbonyl groups in the BAL protein, indicators for oxidative reactions in the respiratory tract, were lowered (p < .03) immediately after the beginning of chronic sulfur(/\/) exposure. This indicates either a lowered oxidant burden andlor an increased antioxidant capacity in the lungs. The enzyme @-Nacetylglucosaminidase increased significantly (p < .05) in the EAL fluid. This increase might be due to enhanced release of lysosomal compounds mediated by sulfite. It did not result from damage of BAL cells, since their viability was not impaired during exposure. Alveolar macrophages (AM) showed a lowered in vitro phagocytosis rate (p < .05) for polystyrene particles and a reduced production (p < .05) of oxygen-derived free radicals after stimulation with opsonized zymosan. These results indicate a reduction in the nonspecific defense capacity of the AM. In conclusion, chronic exposure to an S(IV) aerosol at low concentration might initiate pathobiochemical pathways in the lungs, indicating a potential health hazard.
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