Face down Embedding technique II

THE DISPENSING SLIDE

These simple transparent vinyl slides provide an easy way to precisely place tissues into the embedding wells. The slides allow placement in any orientation to the desired site in the well. They are also a safe conveyance to carry tissue to the cryostat.

The set up

-These are best kept conveniently next to the cutting board standing in a container such as a jar or pencil holder.
-It is handy to keep a large flat paper towel between the cutting board and cryostat to place the slides on when loaded with a specimen. I call this a launch pad. If the cryostat is a distance from the cutting board it would be useful to have a small tray to place the loaded slides on.

The how to

-There are two different size slides. Each with two different sized tips. Choose the tip which best accommodates the tissue and well size.

Place a thin layer of embedding medium at the end of the dispensing slide. Don't omit the medium because it creates a clean plane of separation of the tissue and the well floor an will prevent residual sticking of tissue..
Place a drop of medium at the end of the slide. Gently glide of the slide over a paper towel. This produces a thin uniform layer of medium on the dispensing slide. When the slide is pulled out from under the tissue it leaves a thin layer on the tissue which will give us the flattest surface when embedded.

-Place the tissue at the end of the slide. Orient the tissue so the most important aspect can be addressed optimally. This may mean that a critical margin may be just at the edge so that it can be pressed to adhere immediately on first touch on the well. It may be better to have the critical area such as the epidermis of a thin strip of skin leave the slide longitudinally and slowly pressed into position as in the above pictorial. Consider these things and remember the process of pulling the dispensing slide away can be done very slowly while the tissue is manipulated into precise position.

Looking through the slide

This maneuver allows a great deal of control of the tissue so that we can embed the precise face. Looking through the back of the slide adjust the tissue into the desired position. This may be such that the epidermis or margin is visible or to have a tissue on edge. Then as the tissue leaves the slide, guide it to adhere in the desired position.
-When high precision is a factor use a size larger well. It is easier to manipulate the tissues with the extra room.

Friction and the flimsy

When very flimsy loosely adherent membranous tissues are moved along the slide, friction may create a tendency for the flimsy parts to be dragged out of position or run beneath the specimen. Consider this. If this is a critical part of the tissue such as a margin of a breast biopsy, position the tissue such that this flimsy aspect is right at the edge of the slide, or have it come off the slide longitudinally and manipulate this flimsy aspect into position.
Precision can be maximized using Paper embedding with flimsy tissues.

Dealing with the multitudes

When using multiple slides for multiple specimens place them in order on your launch pad so you don’t confuse the specimens. The dispensing slides can be labeled with a marker if confusion is a consideration. If you're working in a small sub-optimal space (like so many of us) it is a good idea to have pre-labeled areas on the launch pad to place the slides. Create a routine way in which you handle multiples. Routines keep us out of trouble.
- Always use a separate slide for different specimens to avoid cross contamination. Multiple pieces from the same specimen can go on the same slide.

Use your imagination

The dispensing slides allow a lot of creativity. The thick embedding medium allows us to fold tissues, stand them on edge, or make membrane rolls that stand nicely on edge when pulled off the slide. Using the narrow tipped slides allows a great deal of articulation within the larger wells. Tissues can be neatly arranged or maneuvered in a variety of situations that you never considered. Try experimenting with different tips on the slides. You may find having one with a finer point for the tiny biopsies is useful. They can be cut easily with a scissor. My first ones were made from rulers.

And if you don't

If you try to avoid using the dispensing slides and just use forceps, you will find yourself touching the tissue to places you don’t want it to. It will adhere. Adherent tissue can be pushed off with the forceps when this happens. The dispensing slides also provide a means of transporting the tissue to the cryostat. The embedding medium adheres tissue to the slide so it will not easily fall off. I would hate to see you try carrying tissue with forceps, drop it, step on it, crush the tissue, fall and hit your head. It could happen!

Care and feeding of dispensing slides
- I find a fast way to clean these is to have a stack of paper towels next to my cutting board. I give the used slide a quick rinse with water and then quickly pull the slide under the top of the stack of towels while pressing on the towel over the slide. This takes only a few seconds. But do it right away. If you let the medium dry on the slide it will need a bit more soaking to clean it off. Don’t use abrasive cleaners on these vinyl slides or they will loose there transparency.