Biophotonics_Concepts_to_Applications

(Dana P.) #1

  • Brightfield microscopyis commonly used to observe color and light intensity
    (brightness) information from a stained specimen. The entire specimen section
    being examined is illuminated and appears bright to the viewer. Most specimens
    are fairly transparent under the microscope and consequently are difficult to
    analyze visually against a plain white background. Thus,cell stainingcan be
    used to add color to the picture, thereby making objects such as cells and their
    components much easier to see. Through the use of different stains, certain cell
    components (e.g., a nucleus, a cell wall, or the entire cell) can be selectively or
    preferentially stained to examine the component structure. Staining may also be
    used to highlight metabolic processes or to differentiate between live and dead
    cells in a sample. However, it is important to note that because the specimen is
    stained prior to being viewed under a microscope, the observed colors are not
    necessarily those of the actual specimen.


Turret with
objective lenses

Stage plate

Light source

Eyepiece

Specimen holder
(e.g., petri dish)

Light path

Fig. 8.3 Example of an
inverted microscope


Rotating objectives

Stage plate

Stereo
eyepiece

Specimen (plant,
zebra fish, mouse)

Bottom illumination

Top illumination

Stereo head

Fig. 8.4 Example of a
stereomicroscope


238 8 Microscopy

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