682
H O N O R B . F E L L A N D L . M . R I N A L D I N I
enzymatically converted to ASA in the cell particles (Mapson, Isherwood and Chen, 1954), especially in the microsomes (Burns et al., 1956;
Hassan and Lehninger, 1956; Isherwood et al., 1960; Chatterjee et al.,
1961). Synthesis from earlier precursors such as glucuronate or gulonate
requires additional enzymes present in the supernatant (Kanfer et al.,
1959; Yamada et al., 1959; Isherwood and Mapson, 1961; Chatterjee
etal, 1961).
C. R E Q U I R E M E N T S OF V I T A M I N C IN C U L T U R E S A N D ITS
E F F E C T ON G R O W T H
We know little about the requirements for vitamin C of cultivated
cells and tissues and next to nothing about their synthetic abilities.
In a brief but penetrating review of ASA in relation to bacteria,
Eddy and Ingram (1953) concluded that there was no satisfactory
evidence for synthesis of true ASA by bacteria and suggested the use
of more specific methods, such as chromatography, to settle this point.
I have not found later reports on this question. On the whole, it seems
probable that ASA is not a growth factor for micro-organisms, and
it would therefore be interesting to find out whether this is because
they can synthesize it, or because they do not utilize it. Some strains,
however, can reduce dehydroascorbic acid (DHA) (Eddy, Ingram and
Mapson, 1952), and ASA can influence unspecifically the growth of
some bacteria, either favourably or unfavourably, due to its acidity,
its effect on redox potentials and the oxidative production of hydrogen
peroxide. It may conceivably act also as a carbon source. These considerations are pertinent to the evaluation of its effects on cultures of
higher cells.
Possibly the best evidence we have of a relation between requirements
and synthesis in tissue cultures comes from the early work of Bonner
and Bonner (1938) on explanted pea embryos. Out of nine varieties
tested, those showing a high growth-response to added ASA were the
ones that contained less endogenous vitamin. Requirement was therefore considered to be inversely related to synthetic capacity. This
interpretation is supported by the work of Virtanen (1949) who showed,
again in peas, that if the cotyledons were removed, the explanted
seedlings became ASA dependent. An interesting feature of this work
is that after a while the cultures became autotrophic. The specificity
of the requirement, however, may be questioned since growth in the
absence of ASA improved by supplying ammonium instead of nitrate
as a nitrogen source. Virtanen concluded that ASA promoted nitrate
reduction by lowering the redox potential. Bonner and Devirian (1939)
cultivated root tips of the seedlings of several defined varieties of peas,
radish, flax and tomatoes and found that none required vitamin C.
H O N O R B . F E L L A N D L . M . R I N A L D I N I
enzymatically converted to ASA in the cell particles (Mapson, Isherwood and Chen, 1954), especially in the microsomes (Burns et al., 1956;
Hassan and Lehninger, 1956; Isherwood et al., 1960; Chatterjee et al.,
1961). Synthesis from earlier precursors such as glucuronate or gulonate
requires additional enzymes present in the supernatant (Kanfer et al.,
1959; Yamada et al., 1959; Isherwood and Mapson, 1961; Chatterjee
etal, 1961).
C. R E Q U I R E M E N T S OF V I T A M I N C IN C U L T U R E S A N D ITS
E F F E C T ON G R O W T H
We know little about the requirements for vitamin C of cultivated
cells and tissues and next to nothing about their synthetic abilities.
In a brief but penetrating review of ASA in relation to bacteria,
Eddy and Ingram (1953) concluded that there was no satisfactory
evidence for synthesis of true ASA by bacteria and suggested the use
of more specific methods, such as chromatography, to settle this point.
I have not found later reports on this question. On the whole, it seems
probable that ASA is not a growth factor for micro-organisms, and
it would therefore be interesting to find out whether this is because
they can synthesize it, or because they do not utilize it. Some strains,
however, can reduce dehydroascorbic acid (DHA) (Eddy, Ingram and
Mapson, 1952), and ASA can influence unspecifically the growth of
some bacteria, either favourably or unfavourably, due to its acidity,
its effect on redox potentials and the oxidative production of hydrogen
peroxide. It may conceivably act also as a carbon source. These considerations are pertinent to the evaluation of its effects on cultures of
higher cells.
Possibly the best evidence we have of a relation between requirements
and synthesis in tissue cultures comes from the early work of Bonner
and Bonner (1938) on explanted pea embryos. Out of nine varieties
tested, those showing a high growth-response to added ASA were the
ones that contained less endogenous vitamin. Requirement was therefore considered to be inversely related to synthetic capacity. This
interpretation is supported by the work of Virtanen (1949) who showed,
again in peas, that if the cotyledons were removed, the explanted
seedlings became ASA dependent. An interesting feature of this work
is that after a while the cultures became autotrophic. The specificity
of the requirement, however, may be questioned since growth in the
absence of ASA improved by supplying ammonium instead of nitrate
as a nitrogen source. Virtanen concluded that ASA promoted nitrate
reduction by lowering the redox potential. Bonner and Devirian (1939)
cultivated root tips of the seedlings of several defined varieties of peas,
radish, flax and tomatoes and found that none required vitamin C.