Chapter 1
Laboratory Equipment

Laboratory equipment

The variety of sophisticated laboratory equipment in a veterinary practice will depend largely on the size and scope of the practice itself. There are several pieces of core equipment that are standard in every practice that performs in-house testing and analysis.

Microscope

Purpose

The microscope is the most important piece of equipment in the veterinary clinic laboratory (Figure 1.1). The microscope is used to review fecal, urine, blood, and cytology samples on a daily basis. Understanding how the microscope functions, how it operates, and how to care for it will improve the reliability of your results and prolong the life of this valuable piece of equipment.

Parts and functions of a compound microscope

1. Arm: Used to carry the microscope.
2. Base: Supports the microscope and houses the light source.
3. Oculars (or eyepieces): The lens of the microscope you look through. The ocular also magnifies the image. The total magnification can be calculated by multiplying the objective power by the ocular power. Oculars come in different magnifications, but 10× magnification is common.
4. Diopter adjustment: The purpose of the diopter adjustment is to correct the differences in vision an individual may have between their left and right eyes.
5. Interpupillary adjustment: This allows the oculars to move closer or further away from one another to match the width of the space between an individual's eyes. When looking through the microscope, one should see only a single field of view. When viewing a sample, always use both eyes. Using one eye can cause eye strain over time.
6. Nosepiece: The nosepiece holds the objective lenses. The objectives are mounted on a rotating turret so they can be moved into place as needed. Most nosepieces can hold up to five objectives.

   Figure 1.1 Parts of a compound microscope.

7. Objective lenses: The objective lens is the lens closest to the object being viewed, and its function is to magnify the object. Objective lenses are available in many powers, but 4×, 10×, 40×, and 100× are standard. The 4× objective is used mainly for scanning. The 10× objective is considered "low power", 40× is "high power" and the 100× objective is referred to as "oil immersion." When the 10× and 40× objectives are used to view images, the terms "low-power field" (LPF) for 10× and "high-power field" (HPF) for 40× are often used. Once magnified by the objective lens, the image is viewed through the oculars, which magnify it further. Total magnification can be calculated by multiplying the objective power by the ocular lens power.

   Example: 10× (ocular lens) × 100× (objective lens) = 1000× total magnification of the specimen

8. Stage: The platform on which the slide or object is placed for viewing.
9. Stage brackets: Spring-loaded brackets, or clips, hold the slide or specimen in place on the stage.
10. Stage control knobs: Located just below the stage are the stage control knobs. These knobs move the slide or specimen either horizontally (x axis) or vertically (y axis) when it is being viewed.
11. Condenser: The condenser is located under the stage. As light travels from the illuminator, it passes through the condenser, where it is focused and directed at the specimen.
12. Condenser control knob: Allows the condenser to be raised or lowered.
13. Condenser centering screws: These screws center the condenser and, therefore, the beam of light. Generally, they do not need much adjustment unless the microscope is moved or transported frequently.
14. Iris diaphragm: This structure controls the amount of light that reaches the specimen. Opening and closing the iris diaphragm adjusts the diameter of the light beam.
15. Coarse and fine focus adjustment knobs: These knobs bring the object into focus by raising and lowering the stage. Care should be taken when adjusting the stage height. When a higher-power objective is in place (100× objective, for example), there is a risk of raising the stage and slide and hitting the objective lens. This can break the slide and scratch the lens surface.

    Coarse adjustment is used for finding focus under low power and adjusting the stage height. Fine adjustment is used for more delicate, high-power adjustments.

16. Illuminator: The illuminator is the light source for the microscope, usually situated in the base. The brightness of the light from the illuminator can be adjusted to suit your preference and the object you are viewing.

Kohler illumination

What is Kohler illumination?

Kohler illumination is a method of adjusting a microscope in order to provide optimal illumination by focusing the light on the specimen. When a microscope is set up in Kohler illumination, specimens will appear clearer and in more detail (Procedure 1.1).

Procedure 1.1 Setting Kohler

Materials

• Specimen slide (need to focus under 10× power)
• Compound microscope.

Procedure

1. Mount the specimen slide on the stage and focus under 10×.
2. Close the iris diaphragm completely.
3. If the ball of light is not in the center, use the condenser centering screws to move it so that it is centered.
4. Using the condenser adjustment knobs, raise or lower the condenser until the edges of the field become sharp. (See Figures 1.2 and 1.3.)
5. Open the iris diaphragm until the entire field is illuminated.

Figure 1.2 Appearance of image prior to setting the condenser. Note the softer edges of unfocused light.

Figure 1.3 Sharpened edges following condenser adjustment.

When should you set/check Kohler?

• During regular microscope maintenance
• After the microscope is moved/transported
• Whenever you suspect objects do not appear as sharp as they could be

Microscope care and maintenance

Routine care and proper maintenance of the microscope will ensure good performance over the years. In addition to this, a properly maintained and clean microscope will always be ready for use at any time (Figure 1.4). Professional cleaning and maintenance should be considered when routine techniques fail to produce optimal performance of the microscope.

Cleaning and maintenance supplies

Dust cover: When not in use, a microscope should be covered to protect it from dust, hair, and any other possible sources of dirt. A dust cover should never be placed over a microscope while the illuminator is still on.

Lens tissue: Lint-free lens tissues are delicate wipes that will not scratch the surface of the oculars or objective. Always ensure that you are using these types of tissues. Never substitute facial tissues or paper towels, as they are too abrasive.

Lens cleaner: Lens cleaning solution assists in removing fingerprints and smudges from lenses and objectives. Apply the lens cleaner to the lens tissue paper and clean/polish the surface.

Compressed-air duster: Using compressed air to rid the microscope of dust particles is far superior to using your own breath and blowing onto the microscope. Compressed air is clean and avoids possible contamination from moisture.

Figure 1.4 Examples of recommended cleaning supplies for the compound microscope.

Microscope cleanup procedure

When the use of the microscope is complete, following proper cleanup procedures will improve the quality of images that are viewed and extend the life of the microscope and its components.

1. Remove the slide from the stage and dispose of it properly.
2. Clean any oil residue or sample material that may have contaminated the stage surface.
3. Lower the stage and move the smallest objective into place.
4. Clean the objective lens and oculars after every use. The order in which they are cleaned is important. Cleaning the 100× objective first and then moving onto other parts will result in immersion oil being spread onto all other components. Using lens tissue and lens cleaner, begin with cleaning the oculars, then the 4× objective, the 10× objective, 40× objective, and finish with the 100× objective lens.

Maintenance tips

1. Whenever the microscope is not in use, turn off the illuminator. This will greatly extend the life of the bulb, as well as keeping the temperature down during extended periods of laboratory work.
2. When cleaning the microscope, use distilled water or lens cleaner. Avoid using other chemicals or solvents, as they may be corrosive to the rubber or lens mounts.
3. After using immersion oil, clean off any residue immediately. Avoid rotating the 40× objective through immersion oil. If this should occur, immediately clean the...