Narcine brasiliensis electric organ was stimulated to fatigue in vivo. Electrical display of organ output and biochemical assay of bound acetylcholine (ACh) and ATP in isolated vesicles were used to assess the state of fatigue relative to denervated control organs of the same fish. A morphometric analysis of the fate of the synaptic vesicle populations in the nerve terminals was carried out. St...

Tucker, and Edwin Chapman (University of Wisconsin, Madison, WI) find that PIP 2 is a plasma membrane dock for synaptotagmin-1 (syt), a transmembrane protein localized in secretory vesicle membranes, when calcium is absent. This dock may ensure speedy and directed fusion in response to calcium influx. The syt dock has two calcium-binding domains in its cytoplasmic region, called C 2 A and C 2 B...

Tucker, and Edwin Chapman (University of Wisconsin, Madison, WI) find that PIP 2 is a plasma membrane dock for synaptotagmin-1 (syt), a transmembrane protein localized in secretory vesicle membranes, when calcium is absent. This dock may ensure speedy and directed fusion in response to calcium influx. The syt dock has two calcium-binding domains in its cytoplasmic region, called C 2 A and C 2 B...

The temperature-sensitive mutant of Drosophila, shibire(ts-1), which is normal at 19 degrees C, but in which endocytosis is reversibly blocked at 29 degrees C, was used to deplete synapses of vesicles by inducing transmitter release while membrane retrieval was blocked. When the synapse was kept at 29 degrees C for 8 min, complete vesicle depletion occurred. However, no compensatory increase in...

Tucker, and Edwin Chapman (University of Wisconsin, Madison, WI) find that PIP 2 is a plasma membrane dock for synaptotagmin-1 (syt), a transmembrane protein localized in secretory vesicle membranes, when calcium is absent. This dock may ensure speedy and directed fusion in response to calcium influx. The syt dock has two calcium-binding domains in its cytoplasmic region, called C 2 A and C 2 B...

Neurotransmitter release is achieved through the fusion of synaptic vesicles with the neuronal plasma membrane (exocytosis). Vesicles are then retrieved from the plasma membrane (endocytosis). It was hypothesized more than 3 decades ago that endosomes participate in vesicle recycling, constituting a slow endocytosis pathway required especially after prolonged stimulation. This recycling model p...

In the presence of plasma, the osmotic differential required to trigger lysis of large unilamellar vesicles is significantly decreased with the membrane tension at rupture being reduced from about 36 to about 12 dynes/cm for vesicles composed of palmitoyloleoylphosphatidylcholine: cholesterol (55:45). Despite increasing vesicle sensitivity, however, plasma does not alter the characteristics of ...

Cortical granules of the sea urchin are secreted at fertilization in response to sperm fusion. Approximately 15,000 of these vesicles are tightly tethered to the cytoplasmic face of the egg plasma membrane prior to insemination such that the vesicle-plasma membrane complex may be isolated and manipulated in vitro. Furthermore, this complex remains fusion competent and can thus be used for in vi...

Regulated exocytosis is thought to occur either by “full fusion,” where the secretory vesicle fuses with the plasma membrane (PM) via a fusion pore that then dilates until the secretory vesicle collapses into the PM; or by “kiss-and-run,” where the fusion pore does not dilate and instead rapidly reseals such that the secretory vesicle is retrieved almost fully intact. Here, we describe growing ...