266
J O H N P A U L
with cell cultures and the only positive finding is that thyroxine promotes increased glycolysis (Halevy and Avivi, 1958, 1960; Leslie and
Sinclair, 1959).
V I . S T A B L E D I F F E R E N C E S A M O N G C E L L S
A. C H A R A C T E R I S T I C S OF C E L L STRAINS
Although most studies on the enzyme content of cultured cells
indicate that there is a loss of distinctive features (Auerbach and
Walker, 1959; Lieberman and Ove, 1958b) there are numerous exceptions and, for instance, it has already been mentioned that individual
cell strains may present peculiarities, such as the capacity to use xylose
preferentially as a carbohydrate source or the inability to utilize
galactose.
Differences of a more general kind also persist in vitro. For instance
glucose-6-phosphatase is claimed to be present in greater amounts in
epithelial cells than in fibroblastic ones (Paul, 1959) and some rather
general quantitative differences in the respiration and utilization of
carbohydrate pathways in several cell strains have been found. Thus,
when allowance is made for the influence of environmental factors,
differences in respiration can still be observed between cell strains
(Table I V ) . The most marked differences are between large cells, like
HeLa, with a respiration of about 10~
5 ^1 0 2 /h/cell and small ones like
the mouse ascites tumour lymphoma L5178 which has a respiration of
the order of 10~
6 /d/h/cell. Most other cells fall within these limits and
in general the values found seem to be roughly related to the amount
of cytoplasmic material (e.g. Phillips, Andrews and Skank, 1960.
found that the best reference material for respiration is dry weight).
Glycolysis is more variable and it is more difficult to generalize
about it. Nevertheless it has been claimed that the rate of glucose
utilization is a characteristic feature of each cell strain (Bryant et al.,
1958). Particularly if glycolysis is measured in anaerobic conditions,
marked and constant differences are found from one strain to another
(Woods et al., 1959). Furthermore, if aerobic glycolysis is determined at
different pHs, other factors being kept constant, the amount of glycolysis persisting at acid p H varies from strain to strain (Paul et al., 1965).
Some, like strain L, oxidize lactic acid more rapidly than they produce
it below p H 7-2 whereas others, like a hamster fibroblast ( C I 3 ) , still
produce large amounts of lactic acid at p H 6-5. This behaviour is
relatively constant for any strain.
A few other characteristic differences in carbohydrate metabolism
have been described. For instance, the effect on respiration of varying
J O H N P A U L
with cell cultures and the only positive finding is that thyroxine promotes increased glycolysis (Halevy and Avivi, 1958, 1960; Leslie and
Sinclair, 1959).
V I . S T A B L E D I F F E R E N C E S A M O N G C E L L S
A. C H A R A C T E R I S T I C S OF C E L L STRAINS
Although most studies on the enzyme content of cultured cells
indicate that there is a loss of distinctive features (Auerbach and
Walker, 1959; Lieberman and Ove, 1958b) there are numerous exceptions and, for instance, it has already been mentioned that individual
cell strains may present peculiarities, such as the capacity to use xylose
preferentially as a carbohydrate source or the inability to utilize
galactose.
Differences of a more general kind also persist in vitro. For instance
glucose-6-phosphatase is claimed to be present in greater amounts in
epithelial cells than in fibroblastic ones (Paul, 1959) and some rather
general quantitative differences in the respiration and utilization of
carbohydrate pathways in several cell strains have been found. Thus,
when allowance is made for the influence of environmental factors,
differences in respiration can still be observed between cell strains
(Table I V ) . The most marked differences are between large cells, like
HeLa, with a respiration of about 10~
5 ^1 0 2 /h/cell and small ones like
the mouse ascites tumour lymphoma L5178 which has a respiration of
the order of 10~
6 /d/h/cell. Most other cells fall within these limits and
in general the values found seem to be roughly related to the amount
of cytoplasmic material (e.g. Phillips, Andrews and Skank, 1960.
found that the best reference material for respiration is dry weight).
Glycolysis is more variable and it is more difficult to generalize
about it. Nevertheless it has been claimed that the rate of glucose
utilization is a characteristic feature of each cell strain (Bryant et al.,
1958). Particularly if glycolysis is measured in anaerobic conditions,
marked and constant differences are found from one strain to another
(Woods et al., 1959). Furthermore, if aerobic glycolysis is determined at
different pHs, other factors being kept constant, the amount of glycolysis persisting at acid p H varies from strain to strain (Paul et al., 1965).
Some, like strain L, oxidize lactic acid more rapidly than they produce
it below p H 7-2 whereas others, like a hamster fibroblast ( C I 3 ) , still
produce large amounts of lactic acid at p H 6-5. This behaviour is
relatively constant for any strain.
A few other characteristic differences in carbohydrate metabolism
have been described. For instance, the effect on respiration of varying