The

transmission electron microscope Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a gr ...

(TEM) is used as an important

diagnostic tool Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine "cause and effect". In systems engineer ...

to screen human tissues at high magnification (the ultrastructural level), often in conjunction with other methods, particularly light microscopy and immunofluorescence techniques. The TEM was first used extensively for this purpose in the 1980s, especially for identifying the markers of cell differentiation to identify tumours, and in

renal disease Kidney disease, or renal disease, technically referred to as nephropathy, is damage to or disease of a kidney. Nephritis is an inflammatory kidney disease and has several types according to the location of the inflammation. Inflammation can b ...

. Immunolabelling techniques are now generally used instead of the TEM for tumour diagnosis but the technique retains a critical role in the diagnosis of renal disease and a range of other conditions. Specifically, TEM should be used for diagnostic purposes when it: (1) provides useful (complementary) information in the context of a carefully considered differential diagnosis; (2) provides an ‘improved’ diagnosis that results in better treatment strategies and; (3) is time &

cost effective Cost-effectiveness analysis (CEA) is a form of economic analysis that compares the relative costs and outcomes (effects) of different courses of action. Cost-effectiveness analysis is distinct from cost–benefit analysis, which assigns a monetar ...

in respect to alternative techniques. For diagnostic purposes solid tissues are prepared for TEM in the same way as other biological tissues, they are fixed in glutaraldehyde and

osmium tetroxide Osmium tetroxide (also osmium(VIII) oxide) is the chemical compound with the formula OsO4. The compound is noteworthy for its many uses, despite its toxicity and the rarity of osmium. It also has a number of unusual properties, one being that the ...

then dehydrated and embedded in epoxy resin. The epoxy resin block is trimmed and the target tissue is selected using a light microscope by viewing semithin sections stained with toluidine blue. The block is then retrimmed and the specific area for observation is ultrathin sectioned, preferably using a diamond knife. The ultrathin sections are collected on 3mm copper (mesh) grids and stained with

uranyl acetate Uranyl acetate is the acetate salt of uranium oxide, a toxic yellow-green powder useful in certain laboratory tests. Structurally, it is a coordination polymer with formula UO2(CH3CO2)2(H2O)·H2O. Structure In the polymer, uranyl (UO22+) ...

and lead citrate to make the contents of the tissue electron dense (and thus visible in the

electron microscope An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...

References

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External links

The Association of Clinical Electron Microscopists (UK)
Microscopy