Über die Entwicklung des Polypen vonEctopleura dumortieri van Beneden und die Verbreitung der planktischen Stadien in der südlichen Nordsee (Athecatae-Anthomedusae)

Ohne Zusammenfassung     

Die Aktivitätsperiodik der weissen Maus im Kunsttag von 16–29 Stunden Länge

Zusammenfassung Die Tagesperiodik der weißen Maus folgt dem langsam bis zu 21 Std verkürzten oder bis zu 27 Std verlängerten Kunsttag. Dabei verschiebt sich ihr Hauptmaximum im verkürzten Tag in die Dunkelzeit, im verlängerten Tag in die Lichtzeit. Die Verlagerung wird als Resultante zweier Kräfte angesehen: die endogene Komponente der Tierperiodik sucht ihre Eigenperiodik beizubehalten, der Zeitgeber zwingt dem Tier eine davon abweichende Frequenz auf.Dem auf mehr als 20 Std verkürzten oder auf 28 Std verlängerten Kunsttag vermag sich die Maus nicht anzupassen. Ebenso wie im plötzlich verkürzten oder verlängerten Tag stellt sie eine von der Zeitgeberfrequenz unabhängige Eigenperiodik ein. Die Eigenperiodik verhält sich wie im Dauerlicht oder Dauerdunkel: Fallen die Hauptaktivitätsschübe in die Lichtzeit, verlängert sich die Periodendauer auf etwa 26 Std, liegen sie in der Dunkelzeit, verkürzt sie sich auf etwa 23 Std.Dem 20- und 28-Std-Tag ist das Tier teilangepaßt. Die vorwiegend exogen durch den Lichtreiz gebildeten Morgenmaxima folgen noch dem Zeitgeber, die endogenen Hauptmaxima der Eigenperiodik des Tieres: es überlagern sich 2 verschiedene Frequenzen der Tierperiodik.Die Ergebnisse aller Untersuchungen weisen erneut auf die wesentliche Rolle einer endogenen Anlage der Tierperiodik hin.     

Über den Nahrungserwerb der Calyptraeidae (Gastropoda Prosobranchia)

Ohne Zusammenfassung(Mit 27 Abb. und 2 Tabellen im Text)     

AN ELECTRON MICROSCOPE STUDY OF THE DEVELOPMENT OF SV40 VIRUS

Kidney cells, predominantly from Cercopithecus monkeys but also from baboons, were infected in vitro with the SV40 virus. The infectious cycle was studied with the electron microscope by means of thin sections of cells fixed from 3 hours up to 11 days after infection. The frequency of virus formation and various nuclear and cytoplasmic lesions in relation to the infection are described. The virus particles appear in the nucleus in close contact with the chromatin. In a small number of cells they have been observed as early as 10 to 12 hours after infection, but most often they appear 24 to 48 hours afterward. Their mean diameter is 33 mµ. They have no membrane and are frequently arranged as crystal-like structures. In addition to the appearance of virus, one observes various lesions in the nucleoplasm and particularly in the nucleolus, which shows an early hypertrophy and produces unusual, dense condensations in contact with the nucleolonema. The importance of these nucleolar lesions and the relationship between the SV40 virus and the polyoma, common wart, and Shope papilloma viruses are discussed.     

Actin,microtubules and focal adhesion dynamics during cell migration

Cell migration is a complex cellular behavior that results from the coordinated changes in the actin cytoskeleton and the controlled formation and dispersal of cell-substrate adhesion sites. While the actin cytoskeleton provides the driving force at the cell front, the microtubule network assumes a regulatory function in coordinating rear retraction. The polarity within migrating cells is further highlighted by the stationary behavior of focal adhesions in the front and their sliding in trailing ends. We discuss here the cross-talk of the actin cytoskeleton with the microtubule network and the potential mechanisms that control the differential behavior of focal adhesions sites during cell migration.     

Characterization of the KG1a cell line for use in a cell migration based screening assay

High-throughput screening has become a popular method used to identify new “leads” for potentially therapeutic compounds. Further screening of these lead compounds is typically done with secondary assays which may utilize living, functioning cells as screening tools. A problem (or benefit) with these cell-based assays is that living cells are very sensitive to their environment. We have been interested in the process of stem cell migration and how it relates to the cellular therapy of bone marrow transplantation. In this study we describe a secondary, cell-based assay for screening the effects of variousin-vitro conditions on Immature Hematopoietic Cell (IHC) migration. Our results have revealed many subtle factors, such as the cell's adhesive characteristics, or the effect of a culture's growth phase, that need to be accounted for in a screening protocol. Finally, we show that exponentially growing KG1a cells (a human IHC cell line) were 10 times more motile than those in the lag or stationary phases. These data strongly suggest that KG1a cells secrete a chemokinetic factor during the exponential growth phase of a culture.