Selected applications of laser scissors and tweezers and new applications in heart research.

This contribution bridges the gap from early European contributions via laser micromanipulation to recent work on the use of laser microbeams and optical tweezers in studies of basic aspects of heart infarction. Laser transfection, particularly of plant cells and their chloroplasts, and laser microdissection of chromosomes with subsequent generation of chromosome segment-specific DNA libraries and laser-induced cell fusion are reported. With optical tweezers, microgravity can be simulated in roots of the alga Chara. Surprisingly, microgravity reduces growth. In some plant cells, CW lasers, in principle suited primarily for optical tweezers, can be used as microbeam. Also, it is shown that natural killer cells mount an attack on leukemia cells even in the absence of specificity, just induced by exerting force with optical tweezers. Finally, with the help of a laser microbeam, lesions can be induced to study wound healing after heart infarction. A modification of optical tweezers, the erythrocyte-mediated force application (EMFA) technique can be used to induce calcium waves not only in tissue reconstituted from excitable heart muscle cells but also from nonexcitable fibroblasts.