Basal body movements as a mechanism for mitochondrial genome segregation in the trypanosome cell cycle

The mitochondrial genome of Trypanosoma brucei is organized in the form of a complex catenated network of circular DNA molecules. This mass of DNA, known as the kinetoplast, is present at a unique site in the single mitochondrion, and is replicated in a discrete, periodic S phase of the cell cycle. The single-copy nature of the kinetoplast suggests that there is a mechanism ensuring segregation fidelity of replicated copies to each daughter cell. Historically, speculation regarding the nature of this mechanism has often attributed significance to the close association between the kinetoplast and the flagellum basal body. We provide here direct evidence that this mitochondrial DNA complex is indeed linked to the basal body, and segregation of the kinetoplast DNA is dependent on a microtubule-mediated separation of the new and old flagellar basal bodies during the cell cycle. This unique system may represent the remnants of an evolutionarily archaic mechanism for genome segregation.     

Influence du glucose sur le transport intestinal de la phénylalanine en présence et en absence de dinitrophénol

Summary Glucose inhibits the accumulation ofl-phenylalanine by rat intestinal slices during 45-minute incubations. In the presence of DNP (which alone abolishes all active transport), glucose, but not galactose, significantly stimulates amino-acid uptake. However, during short incubations, glucose inhibits the entry of phenylalamine into the tissue, both in the presence and absence of DNP.

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Ce travail a été subventionné par le Fonds National Suisse. Nous tenons à remercier MllesC. Brandt etU. Pässler pour leur aide technique efficace.