Extraterritoriality: A Candian Perspective

Extraterritoriality, or ET as it is known in the trade, has long been a controversial subject in international law. In recent years, several dramatic examples of its application have raised its profile considerably. Perhaps the most glamorous treatment of extraterritoriality is E.T., the recent fil abou the dilemmas an unusual creature faces when he finds himself trapped in a foreign jurisdiction

Extraterritoriality: A Candian Perspective

Extraterritoriality, or ET as it is known in the trade, has long been a controversial subject in international law. In recent years, several dramatic examples of its application have raised its profile considerably. Perhaps the most glamorous treatment of extraterritoriality is E.T., the recent fil abou the dilemmas an unusual creature faces when he finds himself trapped in a foreign jurisdiction

Microtubules Remodel Actomyosin Networks in Xenopus Egg Extracts via Two Mechanisms of F-Actin Transport

Interactions between microtubules and filamentous actin (F-actin) are crucial for many cellular processes, including cell locomotion and cytokinesis, but are poorly understood. To define the basic principles governing microtubule/F-actin interactions, we used dual-wavelength digital fluorescence and fluorescent speckle microscopy to analyze microtubules and F-actin labeled with spectrally distinct fluorophores in interphase Xenopus egg extracts. In the absence of microtubules, networks of F-actin bundles zippered together or exhibited serpentine gliding along the coverslip. When microtubules were nucleated from Xenopus sperm centrosomes, they were released and translocated away from the aster center. In the presence of microtubules, F-actin exhibited two distinct, microtubule-dependent motilities: rapid (∼250–300 nm/s) jerking and slow (∼50 nm/s), straight gliding. Microtubules remodeled the F-actin network, as F-actin jerking caused centrifugal clearing of F-actin from around aster centers. F-actin jerking occurred when F-actin bound to motile microtubules powered by cytoplasmic dynein. F-actin straight gliding occurred when F-actin bundles translocated along the microtubule lattice. These interactions required Xenopus cytosolic factors. Localization of myosin-II to F-actin suggested it may power F-actin zippering, while localization of myosin-V on microtubules suggested it could mediate interactions between microtubules and F-actin. We examine current models for cytokinesis and cell motility in light of these findings