Clathrin-coated buds and dynamin-coated tubules morphologically similar to corresponding structures observed in synaptic membranes can be generated on protein-free liposomes by incubation with cytosol, or with clathrin coat proteins and purified dynamin, respectively. Dynamin- and clathrin-coated intermediates may form independently of each other, despite the coupling between the two processes typically observed in synaptic membranes. Formation of both structures on liposomes can occur in the absence of nucleotides. These findings indicate that interfaces between lipids and cytosolic proteins are fully sufficient to deform lipids bilayers into buds and tubules. They suggest that a main function of membrane proteins is to act as positive and negative regulators of coat assembly, therefore controlling these processes in time and space.

Fission of clathrin-coated and other endocytic vesicles from the plasma membrane involves the cooperation of several membrane-associated proteins, among which the GTPase dynamin plays a key role (1, 2). The participation of dynamin in the fission of endocytic vesicles has been established by a variety of experimental approaches in Drosophila, cultured cells, and cell-free systems, although the precise mechanism of fission and the role of dynamin in this reaction remain unclear (3).Several dynamin partners thought to participate in dynamin recruitment or function have been identified (3,4). At the synapse, where endocytosis plays a key role in the recycling of synaptic vesicle membranes, two prominent dynamin partners are amphiphysin and endophilin (5-7). Amphiphysin has a three-domain structure with an evolutionarily conserved Nterminal module of ϳ250 amino acids called the Bin/amphiphysin/Rvs (BAR) 1 domain, a variable central region, and a Cterminal Src homology-3 (SH3) domain that binds dynamin. Endophilin has a similar domain structure (2). Although the N-terminal domain of endophilin is substantially divergent in amino acid composition from the BAR domain of amphiphysin, it shares some similarity at critical sites, leading to its classification as a BAR domain (8).2 Accordingly, the BAR domains of amphiphysin and endophilin share functional similarities because they both can bind and deform lipid bilayers and mediate homo-and heterodimerization (6, 8 -10). Dynamin also can bind and deform lipid bilayers, and it has been proposed that endophilin and amphiphysin might help to recruit and possibly assist dynamin in the generation of membrane curvature at endocytic pits (8, 10).The closest homologue of amphiphysin and endophilin in Saccharomyces cerevisiae is Rvs167, that forms a stable heterodimer with Rsv161; Rvs167 has a domain structure like amphiphysin, whereas Rvs161 (homologous to the mammalian protein Bin3) possesses only a BAR domain. Mutation of either one or both components of this heterodimer in yeast produces defects in endocytosis and actin function (11). Such a dual phenotype is typical of most mutations in actin regulatory and endocytosis genes in yeast (12). These observations, together with results from a variety of studies in mammalian cells, have suggested a link between endocytosis and actin, although such a link has remained mechanistically elusive (13,14). Foci of actin can often be seen at endocytic sites (15), and endocytic vesicles with actin tails have also been observed (16). Interest-* This work was supported in part by National Institutes of Health Grants NS36251 and CA46128 and United States Army Medical Research and Development Command Grant DAMD17-97-7068) (to P. D. C.); by National Institutes of Health Grant GM58801, a W. M. Keck Distinguished Young Scholar Award, and a McKnight Scholar Award (to F. B. G.); and by National Institutes of Health Grant GM62299 (to J. S.). The costs of publication of this article were defrayed in part by the payment of page charges. This article mu...

This study analyzed Heart Rate Variability in a large sample of active young subjects within a narrow age range (18 to 25), using time and frequency domain methods and a Poincaré plot. Heart rate was recorded (beat to beat) for 30 minutes at rest in 200 healthy subjects divided into 4 groups: 50 sportsmen (20.54 ± 1.52 years); 50 active men (21.22 ± 1.31 years); 50 sportswomen (20.10 ± 1.87 years) and 50 active women (20.92 ± 1.87 years). Significant differences were found for most parameters between athletes and active subjects (male and female) but not between genders. Percentile distributions were provided for all parameters (according to gender and physical activity level) to be used as references in future researches.