Molekularbiologie der Gametenvereinigung

Contact between gametes takes place on a molecular basis via receptors on the surface of the egg coat. The functional part of this receptor glycoprotein is limited to the O-glycosidic-linked carbohydrate side chains, and a polypeptide chain of it may induce an acrosomal reaction on the sperm head, thereby inducing penetration of the sperm into the egg cell. Another function of sperm receptors is to block polyspermy, probably due to modification by limited proteolysis of the receptor glycoprotein. Fertilization is likely to be inhibited by steric hindrance of the receptor due to antibodies specific for glycoproteins of the egg coat. The study of gamete interactions on a molecular basis may serve as a model for intercellular recognition in general.     

Die Struktur der Eukaryonten-Chromosomen

Recent models for the organization of the chromosomes of eukaryotes in mitosis and interphase are discussed with respect to their condensation hierarchy. Possible functional interpretations are indicated. At present, an alternating coiling and loop formation, induced by histones and nonhistone proteins, respectively, appears to be the most probable structure. The relationship of DNA properties to chromatin structure and function is also briefly discussed.     

Die Funktion der Nierenmembranen

Plasma membranes were isolated from rat kidney and their transport properties for sodium, calcium, protons, phosphate, glucose, lactate, and phenylalanine were investigated. The results demonstrate that the luminal plasma membrane, which is in contact with the primary urine, and the contraluminal plasma membrane, which is in contact with the interstitial fluid, differ in their content of ion-sensitive ATPases and sodium-cotransport systems. This allows conclusions on the mechanism of renal transport in which luminal and contraluminal membranes are arranged functionally in series.     

Die Entwicklung der Erdrinde

The key and the well established basis for our present understanding of the evolution of the earth's lithosphere is the continous creation of new oceanic lithosphere in the mid oceanic ridge system. Paleomagnetic evidence and the concept of global plate tectonics permit a quantitative reconstruction of the kinematic history of the lithosphere for the past 200 m.y. This leads to continent configurations very similar to those proposed by A. Wegener. Plate tectonic processes can be traced back until Precambrian times. Before that, due to the generally higher temperature of the earth, the evolution was apparently governed by different processes. Thermal convection and gravitational instabilities are considered as driving forces for the lithosphere.