30
L
TISSUE EXPOSURE
tion of the osmium tetroxide. Thus we have found this technique very
useful in handling brain tissue.
Needle biopsy specimens usually have proven disappointing, although
even experienced investigators report that one may prove poor while the
next can be fairly good for completely mysterious reasons. No doubt
speed is a limiting factor as well as mechanical disruption. In addition it
should be realized that needle biopsies are apt to contain much tissue
fluid and tissue debris. As indicated previously this can be expected to
destroy the properties of the fixative quickly. No doubt one should pass
the tissue quickly through one or two changes of fresh fixative to flush
away this material within the first few seconds. In this connection blood
samples and sternal puncture marrow do not preserve as well as one
would like because of the inevitably associated serum.
This writer knows of several pathologists, currently doing some of the
most beautiful work with human material, who have completely given
up needle biopsies, and insist upon surgical biopsies instead. Even the
collection of these under the best circumstances presents problems. The
surgeon quite naturally likes to block off circulation before removing
tissue. Yet this is apt to do irreparable damage from our point of view.
Furthermore, the surgeon must be educated not to maul the tissue or
leave it sitting on towels. The responsible investigator, rather than a
technician, had better be in the surgery himself, and must have discussed
the problem with the surgeon in advance. Then a small snip of otherwise
undamaged tissue, promptly minced, may yield satisfactory results.
One might think that satisfactory surgical biopsies of the skin or of the
mucous membranes of body orifices would be easy to obtain, yet experience has shown that there are great difficulties, and very few good micrographs have been published. It seems reasonable to think that a tissue
infiltrated with a local anesthetic will not be satisfactory, so emphasis
should be upon tissue obtained under general anesthesia. These regions
of the body, in general, have a dense connective tissue dermis or lamina
propria. Fixation might be improved with hyaluronidase pretreatment
as discussed in the previous section. However, a primary fixation with an
aldehyde fixative should suffice under most circumstances.
It is common knowledge and experience that tissues of young animals
can be preserved well more easily than those of old adults. The reasons
for this are not altogether clear, but in part, may be due to differences in
the amount and character of connective tissue elements. One can expect
these differences to be present also in dealing with human material, and,
L
TISSUE EXPOSURE
tion of the osmium tetroxide. Thus we have found this technique very
useful in handling brain tissue.
Needle biopsy specimens usually have proven disappointing, although
even experienced investigators report that one may prove poor while the
next can be fairly good for completely mysterious reasons. No doubt
speed is a limiting factor as well as mechanical disruption. In addition it
should be realized that needle biopsies are apt to contain much tissue
fluid and tissue debris. As indicated previously this can be expected to
destroy the properties of the fixative quickly. No doubt one should pass
the tissue quickly through one or two changes of fresh fixative to flush
away this material within the first few seconds. In this connection blood
samples and sternal puncture marrow do not preserve as well as one
would like because of the inevitably associated serum.
This writer knows of several pathologists, currently doing some of the
most beautiful work with human material, who have completely given
up needle biopsies, and insist upon surgical biopsies instead. Even the
collection of these under the best circumstances presents problems. The
surgeon quite naturally likes to block off circulation before removing
tissue. Yet this is apt to do irreparable damage from our point of view.
Furthermore, the surgeon must be educated not to maul the tissue or
leave it sitting on towels. The responsible investigator, rather than a
technician, had better be in the surgery himself, and must have discussed
the problem with the surgeon in advance. Then a small snip of otherwise
undamaged tissue, promptly minced, may yield satisfactory results.
One might think that satisfactory surgical biopsies of the skin or of the
mucous membranes of body orifices would be easy to obtain, yet experience has shown that there are great difficulties, and very few good micrographs have been published. It seems reasonable to think that a tissue
infiltrated with a local anesthetic will not be satisfactory, so emphasis
should be upon tissue obtained under general anesthesia. These regions
of the body, in general, have a dense connective tissue dermis or lamina
propria. Fixation might be improved with hyaluronidase pretreatment
as discussed in the previous section. However, a primary fixation with an
aldehyde fixative should suffice under most circumstances.
It is common knowledge and experience that tissues of young animals
can be preserved well more easily than those of old adults. The reasons
for this are not altogether clear, but in part, may be due to differences in
the amount and character of connective tissue elements. One can expect
these differences to be present also in dealing with human material, and,