Biomedical subjects
Publications and source records attributed to E Unsöld.
The investigations on rats and pigs showed that the transuretheral haemostasis of the urinary bladder damaged by radiotherapy is possible by means of fibrin adhesion. The spraying procedure has to be carried out by means of a special balloon-catheter in a bladder filled with CO2. During spraying the bladder must be kept constantly free of pressure.
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The therapeutic effect of Nd-YAG laser coagulation in arterial ulcer bleeding seems to be improved by local epinephrine infiltration. The purpose of this animal study was to evaluate the safety of this new therapeutic modality. The effect of Nd-YAG laser on normal and on infiltrated gastric mucosa was compared in acute and chronic experiments on 14 beagle dogs. On exposed normal gastric wall, perforation time and power output were inversely correlated. The required energies are nearly constant at different power levels. After infiltration of sodium chloride as well as of epinephrine into the mucosa, however, perforation time increased four- to five-fold. Volumes of mucosa defects and of the coagulation zones were also lower after pretreatment by infiltration. The results encourage further clinical use of this new therapeutic approach.
Intravenously administered hematoporphyrin derivative photosensitizes tumorous bladder tissue which can then be destroyed selectively by irradiation with red laser light (630 nm). After experimentally developing a concept since 1978 (light diffusion medium, special bladder catheter) to expose the bladder to the therapeutically effective red laser light, the integral photodynamic therapy is meanwhile performed clinically. The experience gained so far demonstrates that especially the multifocal carcinoma in situ up till now difficult to be detected endoscopically represents a new domain for the integral photodynamic therapy.
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Experimental results and initial clinical experience indicates that even carcinoma in situ can be destroyed by integral photodynamic therapy of multifocal bladder carcinoma following tumor-selective photosensitization with a hematoporphyrin derivative. The employment of a light-scattering medium in combination with a special bladder catheter and photodynamically effective red laser light (630 nm) guarantees homogeneous irradiation of the bladder, which thus reaches all tumor foci. The complications observed were transitional dysurias and, in a particular case, regressive shrinkage of the bladder.
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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 degrees 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.
The site of the pulse regeneration in myelinated nerve is generally assumed to be the unmyelinated part of the axon membrane in thr Ranvier node. To check this, a micro-irradiation technique using laser pulses (lambda equals 347 nm, t equals 20 ns) was used to produce morphological lesions of about 1 mum diameter in various regions of the Ranvier node. The electro-physiological functions were monitored parallel to the irradiation. Depending on the localizing of the lesions two types of changes in these functions were observed: 1. If a definite site in the paranodal myelin sheath was damaged without affecting the axon, an action potential could no longer be elicited, although the resting potential as well as the stationary current-voltage behaviour remained unchanged. 2. A damage of the axon resulted in a break down of membrane potential and resistance. In most of the cases the excitability recovered after spontaneous or current induced restitution of the membrane resting potential and resistance. These observations indicate, that structures in the paranodal region are vital for the Na+-activation and inactivation. The membrane potential and stationary current-voltage behavior can be attributed to the axon membrane. A new hypothesis concerning the mechanism of the Na+-activation-inactivation process is suggested.