2 . M E T H O D S
71
Organ cultures of this sort are used for nutritional, metabolic,
functional and pathological studies. For these purposes, long-term experiments are often unnecessary and usually a few days will suffice. In
this field, the organ-culture method competes with the Warburg
tissue-slice technique and the isolated blood-perfused organ-preparations. Over these it has the advantage that a steady metabolic state
can be maintained for several days instead of just a few hours. With
pure cell lines in culture, the metabolic state may be maintained
indefinitely, but these cells are already dedifferentiated and, in such
a propagating system, cell mutation and selection are occurring all the
time, so that the cells studied may be very different from those originally
removed from the animal. In organ culture it is at least certain that
the cells studied are those which were removed from the animal and in
most cases it can be shown that they have undergone no great morphological change.
Mature organs, in contrast to embryonic ones, obtain most of their
energy by respiration and an adequate oxygen supply is therefore
essential for their survival. For this reason they must always be cultured on the surface of the medium. If cultures of reasonable size
(1-5—2 mm in diameter) are to be maintained without central necrosis
it is essential to use an oxygen gas-phase (Trowell, 1952, 1959, 1961a),
except in the case of the retina which is poisoned by oxygen concentrations of 60°/o or more (Lucas and Trowell, 1958). Smaller cultures
can be maintained in air, but the limiting size is then only 0-5-1 -0 mm
in diameter and it is difficult to obtain or prepare cultures of this size
without excessive trauma.
Assuming that the organs are cultured in oxygen, the limiting size
for spherical organs is about 2 mm diameter, and the following organs
from young rats, adult mice or adult bats can be cultured whole: ovary,
adrenal, pituitary, pineal, thyroid, prostate, seminal vesicle, spinal
ganglia, lymph nodes. From the same animals, long narrow tubes
such as the ureter, ductus deferens, uterine horn, bile duct and arteries
can be cultured in infinite length, and thin sheets such as retina, skin,
diaphragm and mesentery in infinite width. But some organs, notably
the liver, lung, kidney and thymus are always much too big, and suitably sized pieces have to be cut out. The liver, lung and thymus have
lobes with attenuated edges and it is best to cut the pieces from these
edges, so as to produce wedge-shaped cultures covered with capsule
above and below. In point of fact, carefully cut pieces of organs usually
survive as well as whole organs (Trowell, 1959). No particular instruments or skill are required for the preparation of cultures of mature
organs. Standard cataract knives, iris forceps and iridectomy scissors
are the most convenient tools.
71
Organ cultures of this sort are used for nutritional, metabolic,
functional and pathological studies. For these purposes, long-term experiments are often unnecessary and usually a few days will suffice. In
this field, the organ-culture method competes with the Warburg
tissue-slice technique and the isolated blood-perfused organ-preparations. Over these it has the advantage that a steady metabolic state
can be maintained for several days instead of just a few hours. With
pure cell lines in culture, the metabolic state may be maintained
indefinitely, but these cells are already dedifferentiated and, in such
a propagating system, cell mutation and selection are occurring all the
time, so that the cells studied may be very different from those originally
removed from the animal. In organ culture it is at least certain that
the cells studied are those which were removed from the animal and in
most cases it can be shown that they have undergone no great morphological change.
Mature organs, in contrast to embryonic ones, obtain most of their
energy by respiration and an adequate oxygen supply is therefore
essential for their survival. For this reason they must always be cultured on the surface of the medium. If cultures of reasonable size
(1-5—2 mm in diameter) are to be maintained without central necrosis
it is essential to use an oxygen gas-phase (Trowell, 1952, 1959, 1961a),
except in the case of the retina which is poisoned by oxygen concentrations of 60°/o or more (Lucas and Trowell, 1958). Smaller cultures
can be maintained in air, but the limiting size is then only 0-5-1 -0 mm
in diameter and it is difficult to obtain or prepare cultures of this size
without excessive trauma.
Assuming that the organs are cultured in oxygen, the limiting size
for spherical organs is about 2 mm diameter, and the following organs
from young rats, adult mice or adult bats can be cultured whole: ovary,
adrenal, pituitary, pineal, thyroid, prostate, seminal vesicle, spinal
ganglia, lymph nodes. From the same animals, long narrow tubes
such as the ureter, ductus deferens, uterine horn, bile duct and arteries
can be cultured in infinite length, and thin sheets such as retina, skin,
diaphragm and mesentery in infinite width. But some organs, notably
the liver, lung, kidney and thymus are always much too big, and suitably sized pieces have to be cut out. The liver, lung and thymus have
lobes with attenuated edges and it is best to cut the pieces from these
edges, so as to produce wedge-shaped cultures covered with capsule
above and below. In point of fact, carefully cut pieces of organs usually
survive as well as whole organs (Trowell, 1959). No particular instruments or skill are required for the preparation of cultures of mature
organs. Standard cataract knives, iris forceps and iridectomy scissors
are the most convenient tools.