Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones

A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer.     

Zur Frage der ChimÄrenbildung und Umstimmbarkeit

Ohne Zusammenfassung     

Spiza?tus alboniger (Blyth) undSpiza?tus nanus Wallace, zwei f?lschlich vereinigte Arten

Ohne Zusammenfassung     

Oekologische Sippen-, Rassen- und Artunterschiede bei V?geln

Ohne ZusammenfassungVortrag, gehalten auf der 61. Jahresversammlung der D. O. G. am 3. Juli 1943.     

Age of menarche in pigtail monkeys (Macaca nemestrina): A cross-sectional survey of perineal tumescence

A four-month survey of perineal tumescence in 131 young female pigtail monkeys ($\text{Macaca nemestrina}$) revealed that most females had begun to swell by the time they were 3 years old. Those that had not begun to swell by that time were generally of lower weight than their peers. Those that tumesced before they were 3 years old tended to be heavier than their peers, but were not necessarily heavier than older, nonswelling females.