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A . M O S C O N A , O . A . T R O W E L L A N D E . N. W I L L M E R
I V . O R G A N C U L T U R E
A. G E N E R A L COMMENTS
A distinction may first be drawn between the culture of embryonic
organs and that of mature organs. The difference is chiefly between
the ends in view.
1. Embryonic Organs
The embryonic rudiments of such organs as limb-bones, teeth, eyes,
gonads and various glands are generally cultured whole. The rudiment
is excised from the embryo (usually chick or mouse) with specially
sharpened knives and needles under a binocular dissecting microscope
(Fell, 1951), an operation requiring considerable skill and experience.
As a rule the purpose of the experiment is morphological; to study
the further growth and differentiation of the organ in vitro, which,
under proper conditions, usually proceeds much as it would have done
in the whole animal. In other words, the organ enlarges as a whole
without diffuse spreading of the tissues; the growth is "organised".
"Unorganized" growth from the surface of the explant and disorganization in the centre, such as occurs in tissue culture must therefore be
discouraged. This distinction between "unorganized" (histotypic or
cytotypic) growth and "organized" (organotypic) growth was first
clearly described by Maximow (1925) though it had been noticed by
Thomson (1914). In organ culture, the peripheral unorganized growth
is discouraged by culturing the organ on the surface of a solid medium
instead of within it, and by transplanting at frequent intervals.
Another reason for culturing the organ on the surface of the medium
is so that it can get enough oxygen, though this is not so important
for embryonic organs as for mature ones. Embryonic tissues, in general,
obtain most of their energy by glycolysis, so they can survive under
somewhat anoxic conditions and it is not necessary to provide an
oxygen gas-phase; air will do. Under these conditions embryonic
organs can grow to a size of about 3 mm, or more in the case of bones,
before central necrosis sets in.
2. Mature Organs
Since these are already fully differentiated, the object is simply to
maintain the status quo. Any sort of growth or de-differentiation must
again be discouraged. Here the term "culture" is not strictly applicable,
"in vitro maintenance" would be more exact, but conventionally the
method is regarded as a branch of organ culture.
A . M O S C O N A , O . A . T R O W E L L A N D E . N. W I L L M E R
I V . O R G A N C U L T U R E
A. G E N E R A L COMMENTS
A distinction may first be drawn between the culture of embryonic
organs and that of mature organs. The difference is chiefly between
the ends in view.
1. Embryonic Organs
The embryonic rudiments of such organs as limb-bones, teeth, eyes,
gonads and various glands are generally cultured whole. The rudiment
is excised from the embryo (usually chick or mouse) with specially
sharpened knives and needles under a binocular dissecting microscope
(Fell, 1951), an operation requiring considerable skill and experience.
As a rule the purpose of the experiment is morphological; to study
the further growth and differentiation of the organ in vitro, which,
under proper conditions, usually proceeds much as it would have done
in the whole animal. In other words, the organ enlarges as a whole
without diffuse spreading of the tissues; the growth is "organised".
"Unorganized" growth from the surface of the explant and disorganization in the centre, such as occurs in tissue culture must therefore be
discouraged. This distinction between "unorganized" (histotypic or
cytotypic) growth and "organized" (organotypic) growth was first
clearly described by Maximow (1925) though it had been noticed by
Thomson (1914). In organ culture, the peripheral unorganized growth
is discouraged by culturing the organ on the surface of a solid medium
instead of within it, and by transplanting at frequent intervals.
Another reason for culturing the organ on the surface of the medium
is so that it can get enough oxygen, though this is not so important
for embryonic organs as for mature ones. Embryonic tissues, in general,
obtain most of their energy by glycolysis, so they can survive under
somewhat anoxic conditions and it is not necessary to provide an
oxygen gas-phase; air will do. Under these conditions embryonic
organs can grow to a size of about 3 mm, or more in the case of bones,
before central necrosis sets in.
2. Mature Organs
Since these are already fully differentiated, the object is simply to
maintain the status quo. Any sort of growth or de-differentiation must
again be discouraged. Here the term "culture" is not strictly applicable,
"in vitro maintenance" would be more exact, but conventionally the
method is regarded as a branch of organ culture.