Showing papers by "Stephen J. Smith published in 2003"

Mitochondria and release at hippocampal synapses

Abstract: Mitochondria are present in some, but not all presynaptic terminals in the hippocampus. Mitochondria are capable of sequestering and storing large amounts of calcium, but it is unclear whether they influence release probability at these synapses. Using FM dye imaging techniques and confocal microscopy, we have examined the relationship between mitochondrial presence/absence and presynaptic vesicle release from rat hippocampal neurones in primary dissociated culture at room temperature. Following staining with the mitochondrial dye mitotracker green, we were able to resolve putative individual mitochondria associated with neuronal processes. The majority of mitochondria were positionally stable, although some exhibited periods of rapid motility (up to 0.4 μm/s) interspersed with periods of immobility. Co-staining with mitotracker green and the synaptic vesicle dye FM 4–64 indicated that 180 of 506 (36%) synapses were devoid of mitochondria. A comparison of vesicular release in response to stimulation at 1 Hz and at 10 Hz revealed no differences in release properties between synapses with and without mitochondria.

High throughput integration of optoelectronics devices for biochip fluorescent detection

Abstract: Miniaturized, portable and robust sensing systems are required for the development of integrated biological analysis systems and their application to clinical diagnostics. This work uses vertical cavity surface emitting lasers (VCSELs), optical emission filters and PIN photodetectors to realize monolithically integrated, near infrared, fluorescence detection systems. The integration of these micro technologies with biochip applications will drastically reduce cost and allow for parallel sensing architectures, which is particularly useful for flow channel arrays such as in capillary array electrophoresis. This paper focuses on the fabrication of integrated fluorescence sensors. Fabrication procedures have been developed to realize intracavity contacted VCSELs and low noise photodetectors, such as selective AlGaAs wet etching and via planarization. A reflow process with positive photoresist has been developed to provide via electrical contacts and to optically isolate the photodetector from the light source. Three-dimensional microstructures can be simply made by this reflow technique. Optical simulations predict that a detection sensitivity lower than 10000 molecules per 104μm2 sample area. Single molecule detection may be possible in certain sensing architectures.