Optically detected magnetic resonance study of defects in undoped, Be-doped, and Mg-doped GaN

Undoped, Be-doped, and Mg-doped GaN samples were investigated with photoluminescence-detected electron paramagnetic resonance (PL-EPR) and electron-nuclear double resonance (PL-ENDOR). Two types of shallow donors and a deep level Be-related complex were measured in Be-doped GaN. One type of shallow donors is probably due to Si contamination. In all investigated samples, distant gallium ENDOR lines were observed which were split by a quadrupole interaction. From this splitting the electrical field gradients (efg’s) at the Ga nuclei in all investigated samples could be determined very precisely. The efg’s were correlated with strain.     

High-dose diltiazem prevents migration and proliferation of vascular smooth muscle cells in various in-vitro models of human coronary restenosis

BACKGROUND: Restenosis after coronary angioplasty is considered to be caused mainly by increased migration and proliferation of smooth muscle cells (SMC). The concept of local, site-specific delivery of pharmacologic therapies has opened the door for new, high-dose drug regimes. METHODS AND RESULTS: SMC were isolated by enzymatic disaggregation with collagenase/elastase from human coronary plaque tissue of 29 patients (pSMC) and post mortem from the coronary media of 33 corpses (mSMC). Endothelial cells were isolated from human umbilical veins by enzymatic disaggregation with collagenase/dispase. By positive reaction with antibodies against smooth muscle alpha-actin and von Willebrand factor cells were identified as SMC or endothelial cells. In proliferation studies 5-150 micrograms/ml diltiazem was added to the culture media of pSMC, mSMC and endothelial cells. After 5 days there was a significant dose-dependent inhibition of cell proliferation (for pSMC with > 50 micrograms/ml, for mSMC with > 25 micrograms/ml, and for endothelial cells with > 5 micrograms/ml). In migration studies the effect of 5-150 micrograms/ml diltiazem on the velocity of migration of pSMC was investigated over a period of 48 h. Administration of diltiazem at concentrations of 100 and 150 micrograms/ml caused a significant inhibition of the migration of pSMC. The cytoskeletal components smooth muscle alpha-actin, vimentin, and alpha-tubulin of pSMC and the expression of von Willebrand factor of endothelial cells were investigated after an incubation period of 5 days with 50 and 150 micrograms/ml diltiazem. In the transfilter coculture model the effect of 50 micrograms/ml diltiazem on mSMC was investigated after mechanical injury of cocultured endothelial cells. Administration of diltiazem at a concentration of 50 micrograms/ml inhibited the development of a neointimal proliferate in the transfilter coculture model significantly (P < 0.001). CONCLUSIONS: A high dose of diltiazem inhibited the migratory and proliferative activities of coronary SMC significantly. In further experimental studies the effect of locally applied high doses of diltiazem on postangioplasty restenosis should be elucidated.     

Ambulatory tubal sterilization using a plastic clip

The ambulant sterilization of the ovarien tubes with the plastic clip represents a notable method among the operative sterilization methods. With this method, failures can be totally avoided. The bloodless proceeding in the intraperitoneal region results in a minimum of operational risks. The postoperative morbidity is 0%. The clip sterilization takes a few minutes and can be done with intubation or Trapanal/fluothane narcosis in the ambulance. The possibility of refertilization is still to be discussed. From April 1974 till April 1975 this method for sterilization was employed in 97 patients. There were no complications or failures seen.