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Autoradiograph
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==Applications== In [[biology]], this technique may be used to determine the tissue (or cell) localization of a radioactive substance, either introduced into a metabolic pathway, bound to a receptor<ref>{{cite journal |vauthors=Kuhar M, Yamamura HI |title=Localization of cholinergic muscarinic receptors in rat brain by light microscopic radioautography |journal=Brain Res. |volume=110 |issue=2 |pages=229β43 |date=Jul 1976 |pmid=938940 |doi=10.1016/0006-8993(76)90399-1|s2cid=36648292 }}</ref><ref>{{cite journal |vauthors=Young WS, Kuhar MJ |title=A new method for receptor autoradiography: [3H]opioid receptors in rat brain |journal=Brain Res. |volume=179 |issue=2 |pages=255β70 |date=Dec 1979 |pmid=228806 |doi=10.1016/0006-8993(79)90442-6 |s2cid=21647100 }}</ref> or enzyme, or hybridized to a nucleic acid.<ref>{{cite journal |vauthors=Jin L, Lloyd RV |title=In situ hybridization: methods and applications |journal=J Clin Lab Anal |volume=11 |issue=1 |pages=2β9 |year=1997 |pmid=9021518 |pmc=6760707 |doi=10.1002/(SICI)1098-2825(1997)11:1<2::AID-JCLA2>3.0.CO;2-F}}</ref> Applications for autoradiography are broad, ranging from biomedical to environmental sciences to industry. === Receptor autoradiography === The use of [[radioligand|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.<ref>{{Cite book|last=Davenport|first=Anthony P.|date=2005-03-25|title=Receptor Binding Techniques|volume=306|url=http://dx.doi.org/10.1385/1592599273|doi=10.1385/1592599273|isbn=1-59259-927-3|s2cid=3691391}}</ref> Once the receptor density is known, ''in vitro'' autoradiography can also be used to determine the anatomical distribution and affinity of a radiolabeled drug towards the receptor. For ''in vitro'' autoradiography, radioligand was directly applying on frozen tissue sections without administration to the subject. Thus it cannot follow the distribution, metabolism and degradation situation completely in the living body. But because target in the cryosections is widely exposed and can direct contact with radioligand, ''in vitro'' autoradiography is still a quick and easy method to screen drug candidates, [[Positron emission tomography|PET]] and [[SPECT]] ligands. The ligands are generally labeled with <sup>3</sup>H ([[tritium]]), <sup>18</sup>F ([[Fluorine-18|fluorine]]), <sup>11</sup>C ([[Carbon-11|carbon]]) or [[Iodine-125|<sup>125</sup>I]] ([[radioiodine]]). Compare to ''in vitro'', ''ex vivo'' autoradiography were performed after administration of radioligand in the body, which can decrease the artifacts and are closer to the inner environment. The distribution of RNA transcripts in tissue sections by the use of radiolabeled, complementary oligonucleotides or ribonucleic acids ("riboprobes") is called [[In situ hybridization|in situ hybridization histochemistry]]. Radioactive precursors of DNA and RNA, [<sup>3</sup>H]-[[thymidine]] and [<sup>3</sup>H]-[[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 <sup>32</sup>P, <sup>33</sup>P, or <sup>35</sup>S. In the realm of behavioral endocrinology, autoradiography can be used to determine hormonal uptake and indicate receptor location; an animal can be injected with a radiolabeled hormone, or the study can be conducted ''in vitro''. ===Rate of DNA replication=== The rate of DNA replication in a mouse cell growing ''in vitro'' was measured by autoradiography as 33 nucleotides per second.<ref name="pmid1095649">{{cite journal |vauthors=Hand R |title=Deoxyribonucleic acid fiber autoradiography as a technique for studying the replication of the mammalian chromosome |journal=J. Histochem. Cytochem. |volume=23 |issue=7 |pages=475β81 |year=1975 |pmid=1095649 |doi= 10.1177/23.7.1095649|doi-access=free }}</ref> The rate of [[Enterobacteria phage T4|phage T4]] DNA elongation in phage-infected [[Escherichia coli|''E. coli'']] was also measured by autoradiography as 749 nucleotides per second during the period of exponential DNA increase at {{convert|37|C}}.<ref>{{cite journal | vauthors = McCarthy D, Minner C, Bernstein H, Bernstein C | year = 1976 | title = DNA elongation rates and growing point distributions of wild-type phage T4 and a DNA-delay amber mutant | journal = J Mol Biol | volume = 106 | issue = 4| pages = 963β81 | pmid = 789903 | doi=10.1016/0022-2836(76)90346-6}}</ref> ===Detection of protein phosphorylation=== [[Phosphorylation]] means the posttranslational addition of a [[phosphate group]] to specific amino acids of proteins, and such modification can lead to a drastic change in the stability or the function of a protein in the cell. Protein phosphorylation can be detected on an autoradiograph, after incubating the protein in vitro with the appropriate [[kinase]] and Ξ³-32P-ATP. The radiolabeled phosphate of latter is incorporated into the protein which is isolated via [[SDS-PAGE]] and visualized on an autoradiograph of the gel. (See figure 3. of a recent study showing that [[CREB-binding protein]] is phosphorylated by [[HIPK2]].<ref name="pmid26247811">{{cite journal | vauthors = Kovacs KA, Steinmann M, Halfon O, Magistretti PJ, Cardinaux JR | title = Complex regulation of CREB-binding protein by homeodomain-interacting protein kinase 2 | journal = Cell Signaling | volume = 27 | issue = 11 | pages = 2252β60 | date = Nov 2015 | pmid = 26247811 | doi = 10.1016/j.cellsig.2015.08.001 | url = https://repository.ist.ac.at/578/1/CLS-D-15-00072R1_.pdf }}</ref>) === Detection of sugar movement in plant tissue === In [[plant physiology]], autoradiography can be used to determine sugar accumulation in leaf tissue.<ref>{{Cite journal|last1=Goggin|first1=Fiona L.|last2=Medville|first2=Richard|last3=Turgeon|first3=Robert|date=2001-02-01|title=Phloem Loading in the Tulip Tree. Mechanisms and Evolutionary Implications|journal=Plant Physiology|volume=125|issue=2|pages=891β899|doi=10.1104/pp.125.2.891|pmid=11161046|pmc=64890|issn=0032-0889}}</ref> Sugar accumulation, as it relates to autoradiography, can described the [[Phloem loading|phloem-loading strategy]] used in a plant.<ref>{{Cite journal|last=Van Bel|first=A J E|date=June 1993|title=Strategies of Phloem Loading|journal=Annual Review of Plant Physiology and Plant Molecular Biology|volume=44|issue=1|pages=253β281|doi=10.1146/annurev.pp.44.060193.001345|issn=1040-2519}}</ref> For example, if sugars accumulate in the [[Leaf|minor veins]] of a leaf, it is expected that the leaves have few [[plasmodesma]]tal connections which is indicative of [[apoplast]]ic movement, or an active phloem-loading strategy. Sugars, such as [[sucrose]], [[fructose]], or [[mannitol]], are [[Radio-labeled|radiolabeled]] with [<nowiki/>[[Carbon-14|14-C]]], and then absorbed into leaf tissue by simple [[diffusion]].<ref>{{Cite journal|last1=Turgeon|first1=R.|last2=Medville|first2=R.|date=1998-09-29|title=The absence of phloem loading in willow leaves|journal=Proceedings of the National Academy of Sciences|volume=95|issue=20|pages=12055β12060|doi=10.1073/pnas.95.20.12055|pmid=9751789|pmc=21764|bibcode=1998PNAS...9512055T |issn=0027-8424|doi-access=free}}</ref> The leaf tissue is then exposed to autoradiographic film (or emulsion) to produce an image. Images will show distinct vein patterns if sugar accumulation is concentrated in leaf veins (apoplastic movement), or images will show a static-like pattern if sugar accumulation is uniform throughout the leaf ([[symplast]]ic movement). ===Other techniques=== This autoradiographic approach contrasts to techniques such as [[positron emission tomography|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. [[Krypton-85]] is used to inspect aircraft components for small defects. Krypton-85 is allowed to penetrate small cracks, and then its presence is detected by autoradiography. The method is called "krypton gas penetrant imaging". The gas penetrates smaller openings than the liquids used in [[dye penetrant inspection]] and [[fluorescent penetrant inspection]].<ref>{{Cite web|url=http://www.asnt.org/publications/materialseval/solution/decsolutions/decsolutions.htm|archiveurl=https://web.archive.org/web/20080720084341/http://www.asnt.org/publications/materialseval/solution/decsolutions/decsolutions.htm|url-status=dead|title=Krypton Gas Penetrant Imaging - A Valuable Tool for Ensuring Structural Integrity in Aircraft Engine Components|archivedate=July 20, 2008}}</ref>
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