9. P R O T E I N M E T A B O L I S M IN C U L T U R E
307
bound hydroxyproline. Labelled proline was observed in the proteins
of the supernatant fraction and in the "small-granule" fraction.
Subsequently, part of the labelled proline appeared as hydroxyproline in a large-granule fraction (approximately 3000 A) and in
fractions of still larger particle size.
A useful technique has recently been described for the purification
and measurement of microgram quantities of radioactive proteins
and nucleic acids from cultured cells, in which the labelled materials
are first fractionated by abbreviated versions of standard methods and
then collected on membrane filters. The radioactivity of the protein
is measured directly after mounting the filters on stainless steel planchets with rubber cement (Kahan, 1960).
It is not possible to refer to all reports of experiments in which various
aspects of protein synthesis have been studied in Tissue Culture;
useful lists of references are to be found in the section entitled "Specialized functions in cell cultures" in a recent review by Levintow and
Eagle (1961). A survey of papers dealing specifically with the study
of the synthesis of keratin in tissues cultivated in vitro is given under
the section "Remarks on keratinization" in an article by Matoltsy
(1960). The amino-acid metabolism of the lens is discussed in Vol. 2,
Chapter 10.
B. I N D U C T I O N A N D R E P R E S S I O N
Although the phenomena of induced protein synthesis and the
inhibition of synthesis by repression are well-known in bacterial systems,
there is comparatively little information on induction or repression
in animal cells. Nevertheless, these phenomena may be responsible
for many processes that occur in animal cells and which are incompletely understood at present. Tissue Culture provides a means of
overcoming the difficulty encountered in experiments with whole
animals, of bringing the inducer or repressor in direct contact with the
cells concerned.
Kato and M o o g (1958) observed that phenylphosphate produced
a significant increase in the alkaline phosphatase content of isolated
fragments of chick duodenum in culture, as compared with fragments
cultured without substrate. Increases in the alkaline phosphatase
activity were also observed in the chick duodenum after direct injection
of phenylphosphate into eggs. It was inferred that the effects on the
duodenum in vivo were not dependent on the mediation of other organs.
Animal cells are freed from the controlling influences of the whole
body once they have been isolated in vitro. Though this is advantageous
in many respects, loss of control of the cells may also lead to simul-
307
bound hydroxyproline. Labelled proline was observed in the proteins
of the supernatant fraction and in the "small-granule" fraction.
Subsequently, part of the labelled proline appeared as hydroxyproline in a large-granule fraction (approximately 3000 A) and in
fractions of still larger particle size.
A useful technique has recently been described for the purification
and measurement of microgram quantities of radioactive proteins
and nucleic acids from cultured cells, in which the labelled materials
are first fractionated by abbreviated versions of standard methods and
then collected on membrane filters. The radioactivity of the protein
is measured directly after mounting the filters on stainless steel planchets with rubber cement (Kahan, 1960).
It is not possible to refer to all reports of experiments in which various
aspects of protein synthesis have been studied in Tissue Culture;
useful lists of references are to be found in the section entitled "Specialized functions in cell cultures" in a recent review by Levintow and
Eagle (1961). A survey of papers dealing specifically with the study
of the synthesis of keratin in tissues cultivated in vitro is given under
the section "Remarks on keratinization" in an article by Matoltsy
(1960). The amino-acid metabolism of the lens is discussed in Vol. 2,
Chapter 10.
B. I N D U C T I O N A N D R E P R E S S I O N
Although the phenomena of induced protein synthesis and the
inhibition of synthesis by repression are well-known in bacterial systems,
there is comparatively little information on induction or repression
in animal cells. Nevertheless, these phenomena may be responsible
for many processes that occur in animal cells and which are incompletely understood at present. Tissue Culture provides a means of
overcoming the difficulty encountered in experiments with whole
animals, of bringing the inducer or repressor in direct contact with the
cells concerned.
Kato and M o o g (1958) observed that phenylphosphate produced
a significant increase in the alkaline phosphatase content of isolated
fragments of chick duodenum in culture, as compared with fragments
cultured without substrate. Increases in the alkaline phosphatase
activity were also observed in the chick duodenum after direct injection
of phenylphosphate into eggs. It was inferred that the effects on the
duodenum in vivo were not dependent on the mediation of other organs.
Animal cells are freed from the controlling influences of the whole
body once they have been isolated in vitro. Though this is advantageous
in many respects, loss of control of the cells may also lead to simul-