28
A . M O S C O N A , O . A . T R O W E L L A N D E . N . W l L L M E R
is likely to produce some degree of disharmony, and therefore of
abnormal behaviour. Since the centre of a rapidly metabolizing tissue
fragment may become anaerobic, because diffusion of oxygen may not
be able to keep pace with its utilization, to slow it down by reducing the
temperature could be advantageous. As against this, however, if
oxidative metabolism is reduced too far, the operation of the various
ionic and water pumps in the cell may be jeopardized. (See also
p. 81.)
Activity can be reduced to an apparent standstill by lowering the
temperature sufficiently, and the process is sometimes reversible.
Cultures of chick periosteal fibroblasts can be preserved in a more or
less dormant condition for days or even weeks by suitable lowering of
the temperature, e.g. to 15°C or thereabouts. Other cells are readily
damaged by such procedures.
Rapid freezing in dry ice or even liquid nitrogen can be used for
maintaining tissues in a viable state provided that glycerol (30%) or
di-methyl sulphoxide (10%) is present in the medium and tissue while
it is being cooled, and provided that the cells are allowed to regain
normal temperatures sufficiently rapidly. There is an optimum rate
both for freezing and thawing. Cultures of such cells may be stored
apparently indefinitely at — 78°C, and it seems likely that the lower the
temperature, even down to — 190°C, the more efficient the storage
(Rey, 1957; Swim, Haff and Parker, 1958; Hauschka, Mitchell and
Niederpruem, 1959; Naginton and Greaves, 1962).
I. SIZE OF TISSUE
In simple media, constructed on the basis just outlined and kept at
the right temperature, cells and tissues can survive and function for
a time. Since, however, there are no added proteins, amino acids or
other nitrogenous food supplies, activity must inevitably be limited, but,
apart from that, the duration of survival depends greatly on the nature
and size of the tissue explanted. In general and within limits set by
the absence of any circulation, larger pieces of tissue tend to survive
better than smaller ones, and smaller pieces of tissue are again usually
more viable than isolated cells, especially when the medium is not
exactly to their liking. Cells can to some extent adapt both themselves
to the medium and the medium to themselves, but obviously the smaller
the number of cells or the larger the volume of medium the more
difficult will it be for them to do so. When fragments of tissue are
explanted, the tissue fluids actually within the tissue may remain
relatively normal and for a time unchanged by the fluid bathing the
tissue as a whole. The extent to which this can happen depends on the
A . M O S C O N A , O . A . T R O W E L L A N D E . N . W l L L M E R
is likely to produce some degree of disharmony, and therefore of
abnormal behaviour. Since the centre of a rapidly metabolizing tissue
fragment may become anaerobic, because diffusion of oxygen may not
be able to keep pace with its utilization, to slow it down by reducing the
temperature could be advantageous. As against this, however, if
oxidative metabolism is reduced too far, the operation of the various
ionic and water pumps in the cell may be jeopardized. (See also
p. 81.)
Activity can be reduced to an apparent standstill by lowering the
temperature sufficiently, and the process is sometimes reversible.
Cultures of chick periosteal fibroblasts can be preserved in a more or
less dormant condition for days or even weeks by suitable lowering of
the temperature, e.g. to 15°C or thereabouts. Other cells are readily
damaged by such procedures.
Rapid freezing in dry ice or even liquid nitrogen can be used for
maintaining tissues in a viable state provided that glycerol (30%) or
di-methyl sulphoxide (10%) is present in the medium and tissue while
it is being cooled, and provided that the cells are allowed to regain
normal temperatures sufficiently rapidly. There is an optimum rate
both for freezing and thawing. Cultures of such cells may be stored
apparently indefinitely at — 78°C, and it seems likely that the lower the
temperature, even down to — 190°C, the more efficient the storage
(Rey, 1957; Swim, Haff and Parker, 1958; Hauschka, Mitchell and
Niederpruem, 1959; Naginton and Greaves, 1962).
I. SIZE OF TISSUE
In simple media, constructed on the basis just outlined and kept at
the right temperature, cells and tissues can survive and function for
a time. Since, however, there are no added proteins, amino acids or
other nitrogenous food supplies, activity must inevitably be limited, but,
apart from that, the duration of survival depends greatly on the nature
and size of the tissue explanted. In general and within limits set by
the absence of any circulation, larger pieces of tissue tend to survive
better than smaller ones, and smaller pieces of tissue are again usually
more viable than isolated cells, especially when the medium is not
exactly to their liking. Cells can to some extent adapt both themselves
to the medium and the medium to themselves, but obviously the smaller
the number of cells or the larger the volume of medium the more
difficult will it be for them to do so. When fragments of tissue are
explanted, the tissue fluids actually within the tissue may remain
relatively normal and for a time unchanged by the fluid bathing the
tissue as a whole. The extent to which this can happen depends on the