Convection induced by hydrostatic pressure in sedimentation velocity experiments

A consideration of the meaning of the second moment method for the determination of sedimentation coefficients reveals potential convective instability in the sedimentation of all reversibly aggregating systems for which dissociation is favored by pressure.     

Ultrastructural differentiation during drosophila neurogenesis in vitro

Drosophila melanogaster neuroblasts differentiate in vitro, and each gives rise to a cluster of about 18 daughter neurons. Electron microscopic observations of single clusters show that axons from daughter neurons form a neuropile within the cluster of cell bodies. The neuropile increases in size and complexity for several hours, during which time chemical, and probably electrotonic, synapses form between neurites. Clear vesicles with diameters of about 35 nm and dense core vesicles with diameters of about 60 and 160 nm were detected. The development of the neuropile indicates that the prerequisite cell recognition phenomena were manifested during differentiation in vitro, and the complexity of the neuropile suggests it may have attained the capacity to process information.