The role of cavitational activity in fragmentation processes by lithotripters.

The role of cavitation during shock wave exposure was poorly understood until now. Cavitational activity produces severe damage to nearby surfaces due to multiple high-speed liquid jets resulting from bubble collapse. These jet impacts can be made visible by microscopy. For investigating the presence of cavitational processes by shock waves outside and even inside of targets, we have performed the following experiments. Natural gallstones and artificial targets were examined microscopically with regard to the effects of shock pulses. Scanning electron and light microscopical investigations revealed regularly typical and uniform microjet impacts within the fissures and split lines. Since these experiments are the continuation of high-speed films of 10,000 frames/s of shock wave actions on targets, it is most likely that the shock wave produces at first split lines through the stone. Then liquid occupies these cracks. But the following shock waves create within these liquid-filled fissures cavitation and, therefore, cause the disintegration of the targets. It now becomes understandable why biliary lithotripsy is less effective than renal lithotripsy: bile fluid is a high-viscous liquid and, therefore, hinders the disintegration of stones more than low-viscous urine. Intervals between the application of shock waves in biliary lithotripsy, therefore, should improve the treatment results.

The mechanisms of stone disintegration by shock waves.

Through interpretation of high-speed films at 10,000 frames per second of shock wave action on kidney stones and gallstones, the mechanism of stone destruction was analyzed in detail. This shows that the interaction of the shock wave with the targets firstly produces fissures in the stone material. Liquid then enters these small cracks. The actual disintegration is caused later by the enormous violence of imploding cavitation bubbles within these small split lines. That cavitation acts inside the stone and causes fragmentation even within the human gallbladder could furthermore be demonstrated by using scanning electron microscopy. These results should lead to a different process in gallstone lithotripsy leaving intervals between the shock wave treatments. This will allow the viscous bile fluids to occupy the fissures of the stones more completely and, therefore, should increase the cavitational activity on the subsequent treatment with shock pulses.

Rapid insorption of small particles in the gut.

Little is known about the uptake of small particles by the epithelium of the gastrointestinal tract. In our study, we investigated the absorption and transport of synthetic and natural particles by means of scanning electron microscopy (SEM). In Wistar rats, closed loops of jejunum with intact mesenteric blood supply were established in ether anesthesia so that we might study the absorption of latex particles of different sizes. After variable absorption times, loops were removed and prepared for examination by microscopic techniques. The average surface of M-cells was 35 +/- 2 microns2, whereas the total number was dependent on follicle size. The proportion of M-cells to absorptive-like enterocytes on follicle epithelium was 1:12. Latex particles were found easily on the surface of M-cells, and for the most part they were surrounded by microfolds. In only 10 min from the time of application, latex beads were concentrated or even included within macrophages of the dome of lymph follicles. The results indicate that primary insorption of small particles occurs in M-cells of Peyer's patches, and time of insorption is dependent on particle size.

[Results of scanning electron microscopy following internal laser sclerostomy]. / Rasterelektronenmikroskopische Befunde nach experimenteller Lasersklerostomie ab interno.

An experimental glaucoma-filtering procedure ab interno, laser sclerostomy, can be performed using the argon and Q-switched Nd:YAG laser. Compared with surgical techniques the advantages of laser sclerostomy are: minor trauma to the conjunctiva and no risk of infection. In this study 28 rabbit eyes were examined by histological techniques and by scanning electron microscopy 2 days or 4 months following laser sclerostomy. The internal fistular ostium as well as the scleral tunnel showed a relatively smooth margin. Two days after laser sclerostomy, endothelial cell damage was found in only a small area directly surrounding the internal ostium; 4 months later all of this damage was repaired.

[Principles of particle resorption in the gastrointestinal tract]. / Prinzipien der Partikelresorption im Magen-Darm-Trakt.

The uptake of allergens by the epithelium of gastrointestinal tract is not sufficiently investigated. This is true especially for the absorption of small particles like spores and pollen. By means of scanning-electron-microscopy it is possible to locate particles easily and to observe absorption solutions of 0.5 micron and 1 micron latex particles, of 15 microns Urtica pollens and of 35 microns Lycopodium spores and further on by cannulation of the thoracic duct the transport of particles was investigated. After a short time of absorption latex particles were found to be concentrated on M-cells of Peyer's patches (PP) and were found in a close contact to macrophages inside the lymph follicles. There was a constant proportion of M-cells to absorptive-like cells in PP from about 1 to 12. Obviously all particles were also transported by thoracic duct lymph. The results obviously indicate: primary absorption of small particles occurs in M-cells of PP; absorption time is dependent on particle size and transport of particles is achieved by abdominal lymph.