Describe techniques of conventional autoradiography
Answers
Answer:Living cells are briefly exposed to a ‘pulse’ of a specific radioactive compound.
The tissue is left for a variable time.
Samples are taken, fixed, and processed for light or electron microscopy.
Sections are cut and overlaid with a thin film of photographic emulsion.
Left in the dark for days or weeks (while the radioisotope decays). This exposure time depends on the activity of the isotope, the temperature and the background radiation (this will produce with time a contaminating increase in ‘background’ silver grains in the film).
The photographic emulsion is developed (as for conventional photography).
Counterstaining e.g. with toluidine blue, shows the histological details of the tissue. The staining must be able to penetrate, but not have an adverse affect on the emulsion.
Alternatively, pre-staining of the entire block of tissue can be done (e.g. with Osmium on plastic sections coated with stripping film [or dipping emulsion] as in papers by McGeachie and Grounds) before exposure to the photographic emulsion. This avoids the need for individually (post-) staining each slide.
It is not necessary to coverslip these slides
The position of the silver grains in the sample is observed by light or electron microscopy Note: the grains are in a different plane of focus in the emulsion overlying the tissue section. Often oil with a x100 objective is used for detailed observation with the light microscope.
These autoradiographs provide a permanent record.
Explanation:
Explanation:
Autoradiography is the bio-analytical technique used to visualize the distribution of radioactive labeled substance with radioisotope in a biological sample.” • It is a method by which a radioactive material can be localized within a particular tissue, cell, cell organelles or even biomolecules.
An autoradiograph is an image on an x-ray film or nuclear emulsion produced by the pattern of decay emissions (e.g., beta particles or gamma rays) from a distribution of a radioactive substance. ... The film or emulsion is apposed to the labeled tissue section to obtain the autoradiograph (also called an autoradiogram).