4.7.
METHACRYLATE EMBEDDING
95
One of the most serious errors that the novice is apt to make in microtomy is to attempt to cut sections that are too wide. This is discussed
more fully later (Chapter 4.19), but the beginner is apt to blame his
troubles on all sorts of things including the embedment rather than on
the proper problem. If he has doubt about the quality of his blocks, he
should beg, borrow, or steal some of known quality from an experienced
laboratory and practice on them. If, however, his blocks are reasonably
hard and horny, and if small, thin, glassy shavings can be cut free-hand
with a sharp razor blade, then probably ultrathin sections can be cut
from them if other aspects of the technique are adequate.
It should be noted that embedded tissue may alter the characteristics
of the plastic to a greater or lesser extent. Then the tissue itself presumably re-enforces the plastic so that when shavings are taken with
a sharp razor, the tissue area may seem harder than its surround. Within
limits, differences of this sort are to be expected and are acceptable. It is
sometimes difficult, however, to distinguish this sort of an inhomogeneity
from those which may derive from inadequate impregnation or polymerization excepting that in the latter case the tissue area may be obviously much softer than its surround.
4.7. Methacrylate Embedding
Methacrylate embedding no longer is being used widely for electron
microscopy. This is partly because macromolecular structure is not as
well preserved as when cross-linked plastics are employed (Chapter 4.9).
It is also because methacrylate is not thermostable during electron bombardment, and fine structure is apt to collapse during specimen viewing
unless sections are "sandwiched" between two supporting films (Chapter
6.10). Nevertheless methacrylate has substantial virtues to recommend
it for some types of work, and it is partly changing fashions that have
brought it to ill repute rather than just its own intrinsic limitations
(Fig. 7).
Admittedly, methacrylate should no longer be used if one's interest
is in macromolecular structure, or even if one's objective is cytological
detail. On the other hand, such large methacrylate sections can be obtained, and they can be stained so easily, that it should find a permanent
application for histological problems, including many pathological
studies, when relatively low magnifications are to be employed. Also, it
METHACRYLATE EMBEDDING
95
One of the most serious errors that the novice is apt to make in microtomy is to attempt to cut sections that are too wide. This is discussed
more fully later (Chapter 4.19), but the beginner is apt to blame his
troubles on all sorts of things including the embedment rather than on
the proper problem. If he has doubt about the quality of his blocks, he
should beg, borrow, or steal some of known quality from an experienced
laboratory and practice on them. If, however, his blocks are reasonably
hard and horny, and if small, thin, glassy shavings can be cut free-hand
with a sharp razor blade, then probably ultrathin sections can be cut
from them if other aspects of the technique are adequate.
It should be noted that embedded tissue may alter the characteristics
of the plastic to a greater or lesser extent. Then the tissue itself presumably re-enforces the plastic so that when shavings are taken with
a sharp razor, the tissue area may seem harder than its surround. Within
limits, differences of this sort are to be expected and are acceptable. It is
sometimes difficult, however, to distinguish this sort of an inhomogeneity
from those which may derive from inadequate impregnation or polymerization excepting that in the latter case the tissue area may be obviously much softer than its surround.
4.7. Methacrylate Embedding
Methacrylate embedding no longer is being used widely for electron
microscopy. This is partly because macromolecular structure is not as
well preserved as when cross-linked plastics are employed (Chapter 4.9).
It is also because methacrylate is not thermostable during electron bombardment, and fine structure is apt to collapse during specimen viewing
unless sections are "sandwiched" between two supporting films (Chapter
6.10). Nevertheless methacrylate has substantial virtues to recommend
it for some types of work, and it is partly changing fashions that have
brought it to ill repute rather than just its own intrinsic limitations
(Fig. 7).
Admittedly, methacrylate should no longer be used if one's interest
is in macromolecular structure, or even if one's objective is cytological
detail. On the other hand, such large methacrylate sections can be obtained, and they can be stained so easily, that it should find a permanent
application for histological problems, including many pathological
studies, when relatively low magnifications are to be employed. Also, it