| 1. |
- Fridberger, Anders, 1966-, et al.
(författare)
-
Measuring hearing organ vibration patterns with confocal microscopy and optical flow
- 2004
-
Ingår i: Biophysical Journal. - : Cell Press. - 0006-3495 .- 1542-0086. ; 86:1, s. 535-543
-
Tidskriftsartikel (refereegranskat)abstract
- A new method for visualizing vibrating structures is described. The system provides a means to capture very fast repeating events by relatively minor modi. cations to a standard confocal microscope. An acousto-optic modulator was inserted in the beam path, generating brief pulses of laser light. Images were formed by summing consecutive frames until every pixel of the resulting image had been exposed to a laser pulse. Images were analyzed using a new method for optical flow computation; it was validated through introducing artificial displacements in confocal images. Displacements in the range of 0.8 to 4 pixels were measured with 5% error or better. The lower limit for reliable motion detection was 20% of the pixel size. These methods were used for investigating the motion pattern of the vibrating hearing organ. In contrast to standard theory, we show that the organ of Corti possesses several degrees of freedom during sound-evoked vibration. Outer hair cells showed motion indicative of deformation. After acoustic overstimulation, supporting cells contracted. This slowly developing structural change was visualized during simultaneous intense sound stimulation and its speed measured with the optical flow technique.
|
|
| 2. |
- Imreh, Gabriela, et al.
(författare)
-
ER retention may play a role in sorting of the nuclear pore membrane protein POM121
- 2003
-
Ingår i: Experimental Cell Research. - 0014-4827 .- 1090-2422. ; 284:2, s. 173-184
-
Tidskriftsartikel (refereegranskat)abstract
- Integral membrane proteins of the nuclear envelope (NE) are synthesized on the rough endoplasmic reticulum (ER) and following free diffusion in the continuous ER/NE membrane system are targeted to their proper destinations due to interactions of specific domains with other components of the NE. By studying the intracellular distribution and dynamics of a deletion mutant of an integral membrane protein of the nuclear pores, POM121, which lacks the pore-targeting domain, we investigated if ER retention plays a role in sorting of integral membrane proteins to the nuclear envelope. A nascent membrane protein lacking sorting determinants is believed to diffuse laterally in the continuous ER/NE lipid bilayer and expected to follow vesicular traffic to the plasma membrane. The GFP-tagged deletion mutant, POM121(1-129)-GFP, specifically distributed within the ER membrane, but was completely absent from the Golgi compartment and the plasma membrane. Experiments using fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) demonstrated that despite having very high mobility within the whole ER network (D = 0.41 +/- 0.11 mum(2)/s) POM121(1-129)-GFP was unable to exit the ER. It was also not detected in post-ER compartments of cells incubated at 15degreesC. Taken together, these experiments show that amino acids 1-129 of POM121 are able to retain GFP in the ER membrane and suggest that this retention occurs by a direct mechanism rather than by a retrieval mechanism. Our data suggest that ER retention might be important for sorting of POM121 to the nuclear pores.
|
|
| 3. |
|
|
