[Histonet] Revealing lymph nodes
Several correspondents report having trouble getting clearing fixatives to
work. Let's look at methods.
(For people new to this issue - we're talking about fixation methods that
render lymph nodes opaque while making the surrounding adipose tissue clear - for
finding lymph nodes in cancer resection specimens.)
1. Overnight fixation is needed.
2. You need an adequate volume of fixative for the amount of tissue to be
fixed, and that can be quite a lot.
3. Before you put the fatty mesenteries in the fixative, you have to slice
them thin enough for the fixative to penetrate them. It's helpful to stir the
container after an hour or so of fixation.
4. Looking for lymph nodes in the fixed tissue remains time-consuming, and it
requires good ventilation.
I've successfully used Davidson's fixative (three parts water, three parts
ethanol, two parts 37% formaldehyde [strong formalin, not buffered], and one
part glacial acetic acid. Of commercial products I've had good results with one
called O-Fix, not so good with at least one of the others.
In the immortal words of Herman Melville's Moby-Dick, chapter 95:
"mincing the horse-pieces of blubber for the pots; an operation which is
conducted at a curious wooden horse, planted endwise against the bulwarks, and
with a capacious tub beneath it, into which the minced pieces drop.... Bible
leaves! Bible leaves! This is the invariable cry from the mates to the
mincer. It enjoins him to be careful, and cut his work into as thin slices as
possible, inasmuch as by so doing the business of boiling out the oil is much
accelerated, and its quantity considerably increased, besides perhaps improving it
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