254
J O H N P A U L
found that up to 5% of the dry weight of HeLa cells consisted of
glycogen while Peppers et al. (1959) and Westfall, Evans, Shannon and
Earle (1953) and Westfall, Evans, Peppers, Hawkins, Bryant, Schilling
and Earle (1958) found three epithelial lines, including two from liver,
capable of storing glycogen. Since, in the animal, carbohydrate storage
is profoundly influenced by hormones the significance of these results is
not clear beyond the fact that they refute the generalization that cultured cells lose the capacity to store carbohydrate as glycogen.
I V . R E L A T I O N S H I P S B E T W E E N E N E R G Y M E T A B O L I S M
A N D O T H E R F U N C T I O N S
A. G E N E R A L M E T A B O L I C S T A T E A N D M E T A B O L I C P A T T E R N
M . Harris (1958) observed that when a population of chick embryonic
heart cells was allowed to grow through a complete growth cycle from
lag phase, through logarithmic phase to stationary phase, a systematic
change in the pattern of metabolism occurred. A high glycolytic rate
was observed during rapid growth and this diminished as the population
became stationary. These results seemed to be in good agreement with
the hypothesis that glycolytic metabolism is associated with rapid
growth whereas aerobic metabolism is associated with conditions
which might be expected to predispose to differentiation. Harris's
observation was confirmed in other systems (Adebonojo, Bensch and
King, 1961; Etingof and Krichevskaya, 1960; Paul, 1959; Munyon
and Merchant, 1959) but it was later found that the fluctuations could
be almost entirely accounted for by three factors: initial leakage of
Krebs cycle intermediates, which occurs from cells of fibroblastic type;
shift of pH, due to accumulation of acid metabolites; and fall in
glucose concentration (Danes and Paul, 1961b; Paul, 1961). When
allowance is made for these factors it is doubtful whether any true
correlation between glycolytic metabolism and rapid growth remains.
B. D E P E N D E N C E OF SPECIFIC M E T A B O L I C F U N C T I O N S
ON SPECIFIC E N E R G Y P A T H W A Y S
This question arises directly out of the one which has just been
considered and three functions are of particular interest: protein
synthesis; nucleic acid synthesis; and cell division. As has already been
pointed out, the formation of some amino acids and the synthesis of
nucleosides are usually dependent on the Krebs cycle and pentose
phosphate shunt pathways respectively, both of which, it may be noted,
are aerobic. The process of mitosis itself is the third function and it must
J O H N P A U L
found that up to 5% of the dry weight of HeLa cells consisted of
glycogen while Peppers et al. (1959) and Westfall, Evans, Shannon and
Earle (1953) and Westfall, Evans, Peppers, Hawkins, Bryant, Schilling
and Earle (1958) found three epithelial lines, including two from liver,
capable of storing glycogen. Since, in the animal, carbohydrate storage
is profoundly influenced by hormones the significance of these results is
not clear beyond the fact that they refute the generalization that cultured cells lose the capacity to store carbohydrate as glycogen.
I V . R E L A T I O N S H I P S B E T W E E N E N E R G Y M E T A B O L I S M
A N D O T H E R F U N C T I O N S
A. G E N E R A L M E T A B O L I C S T A T E A N D M E T A B O L I C P A T T E R N
M . Harris (1958) observed that when a population of chick embryonic
heart cells was allowed to grow through a complete growth cycle from
lag phase, through logarithmic phase to stationary phase, a systematic
change in the pattern of metabolism occurred. A high glycolytic rate
was observed during rapid growth and this diminished as the population
became stationary. These results seemed to be in good agreement with
the hypothesis that glycolytic metabolism is associated with rapid
growth whereas aerobic metabolism is associated with conditions
which might be expected to predispose to differentiation. Harris's
observation was confirmed in other systems (Adebonojo, Bensch and
King, 1961; Etingof and Krichevskaya, 1960; Paul, 1959; Munyon
and Merchant, 1959) but it was later found that the fluctuations could
be almost entirely accounted for by three factors: initial leakage of
Krebs cycle intermediates, which occurs from cells of fibroblastic type;
shift of pH, due to accumulation of acid metabolites; and fall in
glucose concentration (Danes and Paul, 1961b; Paul, 1961). When
allowance is made for these factors it is doubtful whether any true
correlation between glycolytic metabolism and rapid growth remains.
B. D E P E N D E N C E OF SPECIFIC M E T A B O L I C F U N C T I O N S
ON SPECIFIC E N E R G Y P A T H W A Y S
This question arises directly out of the one which has just been
considered and three functions are of particular interest: protein
synthesis; nucleic acid synthesis; and cell division. As has already been
pointed out, the formation of some amino acids and the synthesis of
nucleosides are usually dependent on the Krebs cycle and pentose
phosphate shunt pathways respectively, both of which, it may be noted,
are aerobic. The process of mitosis itself is the third function and it must