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The behavioral responses of Rhodobacter sphaeroides to different light intensities was analyzed to determine the role of the photosynthetic electron transport in microbial photoresponse. Analysis of Rhodobacter sphaeroides photoresponse during reduced electrochemical proton gradients and constant electron transport indicated the role of the photosynthetic electron transport in mediating the response of the microbe to light. Furthermore, the sensitivity of Rhodobacter sphaeroides to light was dependent on the efficiency of its light-harvesting pigments.

Long-wavelength light intensity induced the accumulation of the M412 bacteriorhodopsin photocycle intermediate in Halobacterium salinarum. The H. salinarum mutant strain Pho81-B4, which can synthesize bacteriorhodopsins in the absence of sensory rhodopsins, responded to blue light as a repellent. This response was associated with an increase in membrane electric potential which is dependent on proton pump activity. Changes in the intensity of blue light had no effect on the rate of bacteriorhodopsin synthesis. It was suggested that changes in membrane potential across the membrane mediated the response of bacteriorhodopsin to blue light.

Sensory experience refines neuronal structure and functionality. The visual system has proved to be a productive model system to study this plasticity. In the neonatal retina, the dendritic arbors of a large proportion of ganglion cells are diffuse in the inner plexiform layer. With maturation, many of these arbors become monolaminated. Visual deprivation suppresses this remodeling. Little is known of the molecular mechanisms controlling maturational and experience-dependent refinement. Here, we tested the hypothesis that brain-derived neurotrophic factor (BDNF), which is known to regulate dendritic branching and synaptic function in the brain, modulates the developmental and visual experience-dependent refinement of retinal ganglion cells. We used a transgenic mouse line, in which a small number of ganglion cells were labeled with yellow fluorescence protein, to delineate their dendritic structure in vivo. We found that transgenic overexpression of BDNF accelerated the laminar refinement of ganglion cell dendrites, whereas decreased TrkB expression or retina-specific deletion of TrkB, the cognate receptor for BDNF, retarded it. BDNF--TrkB signaling regulated the maturational formation of new branches in ON but not the bilaminated ON--OFF ganglion cells. Furthermore, BDNF overexpression overrides the requirement for visual inputs to stimulate laminar refinement and dendritic branching of ganglion cells. These experiments reveal a previously unrecognized action of BDNF and TrkB in controlling cell-specific, experience-dependent remodeling of neuronal structures in the visual system. [ABSTRACT FROM AUTHOR]

Examines the synaptotagmin modulation of fusion pore kinetics in regulated exocytosis of dense-core vesicles. Representation of fusion pore opening; Establishment of the existence of fusion pore; Investigation of the possibility of the regulation of fusion pore by synaptotagmin.