Tuesday, January 16, 2018

Fluorescence microscopy



Fluorescence microscopy
In this microscopy, microscopy is stained with fluorescent dye. Fluorescent dye is such kind of substance which absorbs light with particular wavelength and energy then emits light of different wavelength and energy i.e. lower or higher. After staining with dye then substance illuminate with blue light. The blue light is absorbed and green light emits by the dye. Exciter filter used in microscope block blue light and allow green light to pass through and reach the eye.

The fluorescent antibody technique- immunofluorescennce
The bacterial cell is incubated with specific antibody that is conjugated with a fluorescent dye; the dye antibody will cover the surface of the cell. This is a slide technique performed on slide; excess fluorescent dye antibody conjugated is washed off. This preparation is examined by ultraviolet light microscopy. Any bacterial cell which is not covered by the dye does not fluorescence and hence is not visible by this technique.
Specimen seen: Bright and colored; color of the fluorescent dye.
Commonly used for: detecting infectious agents in tissue, detecting immunological reactions.
Advantages
·         Enhances; subcellular anatomy; allows observation of motility.
·         It is more accurate and faster to examine.

Disadvantages
·         Inability to evaluate staining.
·         It is not flexible in all area, expensive and technical complexity.



Wednesday, January 10, 2018

Phase-Contrast Microscopy



Phase-Contrast Microscopy


It is very much difficult to obtain sufficient contrast when living material examined, which has a refractive index not far from that of liquid. This microscope has special optical system which makes it possible to distinguish unstained structures within a cell which differ slightly in their refractive index or thickness. It has special phase-contrast objective with phase contrast condenser. Appearances of specimen varying degree of “darkness”.

Advantages
  • ·         Observing living unstained cell
  • ·         Revealing intracellular structures

Disadvantages
  • ·         Inability to evaluate staining reactions.
  • ·         Difficult to observe thick specimens/ distorted image for thick specimen.

(Note: Refractive index)