Die Pterosaurier

During the Mesozoic the pterosaurs, or flying reptiles, were widely spread over the world. The distribution of the pterosaur fossils shows a restriction to a zone within 40 ° latitude in relation to the paleoequators. Probably all pterosaurs had hairs, thus indicating homoiothermic conditions. The brain structure is similar to the bird's brain but relatively smaller. With regard to certain osteologic features the pterosaurs have to be classified as archosaurs. Their origin is not known and they probably became extinct due to the change of climate during the late Cretaceous.     

Die Polymerase-Kettenreaktion

In an unprecedented short time, the polymerase chain reaction (PCR) has developed into an indispensible analytical tool which facilitates gene analyses and recombinant techniques, enables DNA detection from single cells, and permits sequence determinations even from extinct species. Like the PCR process itself, the number of laboratories making use of this novel technique has been growing exponentially. This report covers critically the PCR from the basic principle to selected examples. It illustrates the strengths of the method: speed, sensitivity, and versatility and discusses aspects which still need improvement and development.     

Die Interferone

Interferons are a family of proteins synthesized by the cells of higher organisms as a first reaction to viral infections, preceding the immune response. They are also involved in the regulation of the immune system and therefore included among the lymphokines. Since they had been shown to have antitumor activity in vitro and in experimental animals, they were suggested to be powerful drugs in cancer therapy.