The most sensitive cellular indicators of autolytic/degenerative change are the mitochondria and endoplasmic reticulum, both of which may show signs of swelling (a reflection of osmotic imbalance) only a few minutes after the cells are separated from a blood supply. In order to preserve the ultrastructure of the cell it is crucial that samples are fixed as soon as possible after the biopsy is taken. Although flaws in lens design restrict this potential, contemporary transmission electron microscopes are capable of resolving structures of 0.2 nm or less. For example, the limit of resolution of a bright-field microscope using glass lenses and white light is around 200 nm, whereas a fluorescence microscope operating with shorter wavelength ultraviolet light is capable of resolving objects around 100 nm apart.īy comparison, using electromagnetic lenses and a beam of electrons accelerated to a potential of 100 kV, an electron microscope is theoretically capable of resolving approximately 0.001 nm. Where R, the resolution, represents the capacity of the optical system to produce separate images of objects very close together, λ is the wavelength of the incident illumination, and NA is the numerical aperture of the lens.Ĭritically, for any given lens, resolution is directly related to the wavelength of the source radiation. The physical basis of this benefit lies in the formula: ![]() ![]() With this greater resolving power the transmission electron microscope is able to reveal the substructure or ultrastructure of individual cells. The fundamental advantage of transmission electron microscopy (TEM) over conventional light microscopy is that the electron microscope has a resolution approximately 1000 times better than the light microscope.
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