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Reconsideration of resolution in EM autoradiography using a biological line source
Author(s) -
Gupta Brij L.,
Moreton Roger B.,
Cooper N. C.
Publication year - 1973
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1973.tb03848.x
Subject(s) - cuticle (hair) , chitin , resolution (logic) , chemistry , materials science , anatomy , biology , biochemistry , artificial intelligence , chitosan , computer science
SUMMARY Pieces of integument containing cuticle and hypodermal cells from the desert locust Schistocerca gregaria were pulse‐labelled to produce very narrow bands of radioactive chitin or resilin in the cuticle. Araldite sections of such cuticle were used as a radioactive line source to test the resolution and the possible effect of self‐absorption due to heavy metal staining of tissue‐sections in EM autoradiographs. The approximate position of the source and the half‐distance of resolution (HD) in EM autoradiographs were determined by replotting the grain‐distribution in integrated form, producing a sigmoid‐shaped curve. The values of HD, the position of the source and the total number of grains were then used to superimpose a theoretical grain‐density distribution function on the experimental grain‐distribution histograms. The results confirm the line or very narrow band nature of the radioactive chitin or resilin in the tissue‐sections used. When the source was resilin situated in the cuticle at about 1 μm from the cell‐surface, the values for HD were 130–180 nm in Ilford L4 and about 100 nm in Agfa‐Gevaert NUC 307. When the source was chitin situated just outside the cell surface, the corresponding value for HD in Ilford L4 was 85–125 nm. Possible adverse effects of electron beam damage on resolution in resilin‐containing samples are discussed. In sections with radioactive chitin at the cell surface, the total number of grains in the cell‐side of the histogram was always significantly lower than that in the cuticle‐side. This marked asymmetry in grain distribution is considered to be indicative of much greater self absorption of beta‐particles from the tritium source, in heavily stained areas of the sections.