Related Experiment Videos
The osmotic behavior of rod photoreceptor outer segment discs
The Journal of Cell Biology
|March 1, 1971
Summary
Frog rod photoreceptor outer segment discs are distinct, membrane-bound organelles. Their membranes exhibit selective permeability, controlling ion and molecule passage, crucial for visual signaling.
Area of Science:
- Biophysics
- Cell Biology
- Photoreceptor Physiology
Background:
- Rod photoreceptors are essential for vision, converting light into electrical signals.
- Understanding the permeability of outer segment discs is key to elucidating visual transduction mechanisms.
Purpose of the Study:
- To investigate the permeability properties of frog rod photoreceptor outer segment discs.
- To determine the nature of the disc membrane and its barrier functions.
Main Methods:
- Direct volume measurement of outer segment fragments.
- Electron microscopy to visualize structural changes.
- Osmotic pressure manipulation using various solutes.
Main Results:
- Disc membranes are impermeable to ions (Na+, K+, Mg+2, Ca+2, Cl-, PO4-3) and sucrose.
- Disc membranes are freely permeable to ammonium acetate.
- Osmotic swelling and contraction indicate changes in intradiscal volume.
- Glutaraldehyde fixation does not abolish permeability properties.
Conclusions:
- Frog rod photoreceptor outer segment discs function as independent, membrane-enclosed compartments.
- The disc membrane acts as a selective barrier, separating the intradiscal space from the photoreceptor cytoplasm.