User: Peter Robin Hiesinger, a neurogeneticist at UT Southwestern Medical Center in Dallas.

Project: Real-time imaging (seconds to minutes) of synaptic transmission at the neuromuscular junction of the developing fly larva; time-lapse imaging (hours to days) of neuronal outgrowth in cultures of developing brain.

Problem: Hiesinger needed a system that could handle both extremely short and extremely long timescales.

Solution: Hiesinger's real-time imaging experiments require the acquisition of as many as 25 images per second. Although a spinning-disk confocal microscope can achieve the speed, it lacks the flexibility to change the pinhole size to restrict out-of-focus illumination and adjust for the sample's level of fluorescence. Instead, Hiesinger chose a Leica resonance-scanning confocal (Leica TCS SP5), essentially a standard laser-scanning confocal microscope, but with...

<figcaption>Top: Cultured developing fly brain labeled with photoreceptor-specific GFP (green) and pan-neuronal RFP (red), imaged in conventional confocal mode. Bottom: Neuromuscular junction in fly larva (blue: muscle; green: presynaptic boutons, red: active zones) imaged in resonant confocal mode. Credit: Top: Peter Robin Hiesinger</figcaption>
Top: Cultured developing fly brain labeled with photoreceptor-specific GFP (green) and pan-neuronal RFP (red), imaged in conventional confocal mode. Bottom: Neuromuscular junction in fly larva (blue: muscle; green: presynaptic boutons, red: active zones) imaged in resonant confocal mode. Credit: Top: Peter Robin Hiesinger

Other companies have recently introduced similar modifications on the traditional confocal microsope, notes Maddox, such as Zeiss' line-scanning (5Live) or Nikon's swept-field (LiveScan) models. Both scan with a slit instead of a pinhole for faster imaging.

Cost: ~$340,000

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