Autoradiograph
Encyclopedia
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. Alternatively, the autoradiograph is also available as a digital image (digital autoradiography), due to the recent development of scintillation
gas detectors or rare earth phosphorimaging systems. In biology, this technique may be used to determine the tissue localization of a radioactive substance, either introduced into a metabolic pathway, bound to a receptor or enzyme, or hybridized to a nucleic acid. The film or emulsion is apposed to the labeled tissue section to obtain the autoradiograph (also called an autoradiogram). The auto- prefix indicates that the radioactive substance is within the sample, as distinguished from the case of historadiography
or microradiography, in which the sample is X-rayed using an external source.
The use of radiolabeled ligands
to determine the tissue distributions of receptors is termed either in vivo
or in vitro
receptor autoradiography if the ligand is administered into the circulation (with subsequent tissue removal and sectioning) or applied to the tissue sections, respectively. The ligands are generally labeled with 3H (tritium
) or 125I
.
The distribution of RNA transcripts in tissue sections by the use of radiolabeled, complementary oligonucleotides or ribonucleic acids ("riboprobes") is called in situ hybridization histochemistry
. Radioactive precursors of DNA and RNA, 3H (thymidine
) and 3 (uridine
) respectively, may be introduced to living cells to determine the timing of several phases of the cell cycle. RNA or DNA viral sequences can also be located in this fashion. These probes are usually labeled with 32P, 33P, or 35S.
This autoradiographic approach contrasts to techniques such as PET
and SPECT where the exact 3-dimensional localization of the radiation source is provided by careful use of coincidence counting, gamma counters and other devices.
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
film or nuclear emulsion
Nuclear emulsion
In a Particle and Nuclear physics, a nuclear emulsion plate is a photographic plate with a particularly thick emulsion layer and with a very uniform grain size. Like bubble chambers, cloud chambers, and wire chambers nuclear emulsion plates record the tracks of charged particles passing through...
produced by the pattern of decay emissions (e.g., beta particles or gamma rays) from a distribution of a radioactive substance. Alternatively, the autoradiograph is also available as a digital image (digital autoradiography), due to the recent development of scintillation
Scintillation (physics)
Scintillation is a flash of light produced in a transparent material by an ionization event. See scintillator and scintillation counter for practical applications.-Overview:...
gas detectors or rare earth phosphorimaging systems. In biology, this technique may be used to determine the tissue localization of a radioactive substance, either introduced into a metabolic pathway, bound to a receptor or enzyme, or hybridized to a nucleic acid. The film or emulsion is apposed to the labeled tissue section to obtain the autoradiograph (also called an autoradiogram). The auto- prefix indicates that the radioactive substance is within the sample, as distinguished from the case of historadiography
Historadiography
Historadiography is a technique formerly utilized in the fields of histology and cellular biology to provide semiquantitative information regarding the density of a tissue sample. It is usually synonymous with microradiography...
or microradiography, in which the sample is X-rayed using an external source.
The use of radiolabeled ligands
Radioligand
A radioligand is a radioactive biochemical substance that is used for diagnosis or for research-oriented study of the receptor systems of the body....
to determine the tissue distributions of receptors is termed either in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
or in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
receptor autoradiography if the ligand is administered into the circulation (with subsequent tissue removal and sectioning) or applied to the tissue sections, respectively. The ligands are generally labeled with 3H (tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
) or 125I
Iodine-125
Iodine-125 is a radioisotope of iodine which has uses in biological assays, nuclear medicine imaging and in radiation therapy as brachytherapy to treat prostate cancer and brain tumors. It is the second longest-lived radioisotope of iodine, after iodine-129.Its half-life is around 59 days and it...
.
The distribution of RNA transcripts in tissue sections by the use of radiolabeled, complementary oligonucleotides or ribonucleic acids ("riboprobes") is called in situ hybridization histochemistry
In situ hybridization
In situ hybridization is a type of hybridization that uses a labeled complementary DNA or RNA strand to localize a specific DNA or RNA sequence in a portion or section of tissue , or, if the tissue is small enough , in the entire tissue...
. Radioactive precursors of DNA and RNA, 3H (thymidine
Thymidine
Thymidine is a chemical compound, more precisely a pyrimidine deoxynucleoside. Deoxythymidine is the DNA nucleoside T, which pairs with deoxyadenosine in double-stranded DNA...
) and 3 (uridine
Uridine
Uridine is a molecule that is formed when uracil is attached to a ribose ring via a β-N1-glycosidic bond.If uracil is attached to a deoxyribose ring, it is known as a deoxyuridine....
) respectively, may be introduced to living cells to determine the timing of several phases of the cell cycle. RNA or DNA viral sequences can also be located in this fashion. These probes are usually labeled with 32P, 33P, or 35S.
This autoradiographic approach contrasts to techniques such as PET
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
and SPECT where the exact 3-dimensional localization of the radiation source is provided by careful use of coincidence counting, gamma counters and other devices.