SELECTING THE MICROSCOPE

The microinjection is carried out on an inverted microscope at a magnification of 200–400×. It is essential to equip the microscope with some form of contrast optics. Originally, only differential interference contrast (DIC) optics (Nomarski) was available. One of the most widely used optics systems is now Hoffman Optics' Modulation Contrast Optics, although Carl Zeiss introduced its low-cost ‘Varel’ system in 1996. The advantage of the latter two optical systems is that they can be used with plastic dishes, whereas DIC optics are optimized for working with glass. Dishes with a glass base are now available from, for example, WillCo Wells B.V. in Amsterdam, allowing DIC to be used as originally intended.

The microscope itself should be of the inverted type. The IX-71 from Olympus, the DM IRB/E from Leica, the Axiovert 200 from Zeiss, and the TE 2000 from Nikon are all good examples. These microscopes are available with a bewildering array of accessories and options. Those options considered important would be a camera port, allowing a simple camera and monitor to be attached (useful for teaching), and a movable stage.

Essential specifications for the microscope are:

• inverted microscope (Zeiss Axiovert series, Olympus IX series, Nikon TE series, Leica DM-IR series);

• 10×, 20×and 40×objectives;

• Nomarski (DIC) or Hoffman optics (note that Nomarski optics are not optimized for use with plastic dishes);

• long or ultra-long working distance condenser;

• mechanical stage, with a long-arm coaxial control;

• heated stage insert.

Recommended options include:

• camera port;

• basic closed-circuit TV camera and monitor;

• anti-vibration plate or table (depending on the level of ambient vibration).