306
J . A . L U C Y
uptake of leucine and methionine by the epidermis, indicating that it
had little action on the total amount of protein synthesized in the deeper
layers of the epidermis; however, it reduced the incorporation of
tyrosine in the superficial layers and greatly diminished that of cystine
throughout the epithelium.
Robertson, Hagerman, Richardson and Villee (1961) have published
a preliminary report on the effects of oestradiol on human endometrium
in tissue culture. Their observations indicated that oestradiol increased
the uptake of glycine from the medium and the incorporation of this
amino acid into the tissue.
An interesting observation that radioactive tyrosine and leucine
were incorporated into serum albumin and into a-, j8-, and y-globulins
by chick mesenchyme was reported by Abdel-Samie, Broda and Kellner
(1960). Similar results were obtained with HeLa cells and human
transformed liver cells ( H L M ) . The identity of the labelled serum
albumin was confirmed immunologically; the authors concluded that
some extra-hepatic tissues have the ability to synthesize serum albumin.
Saunders, Quevedo, Pierro and Morbeck (1955), using explants of
embryonic chick skin in "natural" medium containing added tyrosine
or phenylalanine, showed that explants cultured with tyrosine, were
in general, more intensely pigmented than explants without tyrosine.
O n the other hand, addition of phenylalanine resulted in a reduced
pigment production which could, however, be restored by tyrosine,
thus indicating that synthesis of melanin by embryonic chick melanoblasts is inhibited by phenylalanine.
Kruse and White (1961) have studied changes in protein content
during the growth cycle of primary cultures of mammalian cells
obtained from two different tumours. The protein-nitrogen content
per cell decreased in the lag phase that occurred during the initial
period of cultivation, and then subsequently increased to a higher and
approximately constant value in the logarithmic phase of growth.
These results were in contrast to those obtained by other workers in
experiments with several established cell lines in which an increase of
protein occurred in the lag phase, followed by a decrease during the
logarithmic phase.
Tissue-Culture techniques can be combined with methods in which
sub-cellular particles are used in studies on the mechanism of protein
synthesis. Cell fractionation studies have been made on cultures of
osteoblasts which were grown in the presence of labelled proline and
then homogenized prior to differential centrifugation in sucrose
solution (Jackson, 1958, 1960). The object of these experiments
was to find whether the site of incorporation of free proline into the
proteins of the cell was the same as that of the formation of the protein-
J . A . L U C Y
uptake of leucine and methionine by the epidermis, indicating that it
had little action on the total amount of protein synthesized in the deeper
layers of the epidermis; however, it reduced the incorporation of
tyrosine in the superficial layers and greatly diminished that of cystine
throughout the epithelium.
Robertson, Hagerman, Richardson and Villee (1961) have published
a preliminary report on the effects of oestradiol on human endometrium
in tissue culture. Their observations indicated that oestradiol increased
the uptake of glycine from the medium and the incorporation of this
amino acid into the tissue.
An interesting observation that radioactive tyrosine and leucine
were incorporated into serum albumin and into a-, j8-, and y-globulins
by chick mesenchyme was reported by Abdel-Samie, Broda and Kellner
(1960). Similar results were obtained with HeLa cells and human
transformed liver cells ( H L M ) . The identity of the labelled serum
albumin was confirmed immunologically; the authors concluded that
some extra-hepatic tissues have the ability to synthesize serum albumin.
Saunders, Quevedo, Pierro and Morbeck (1955), using explants of
embryonic chick skin in "natural" medium containing added tyrosine
or phenylalanine, showed that explants cultured with tyrosine, were
in general, more intensely pigmented than explants without tyrosine.
O n the other hand, addition of phenylalanine resulted in a reduced
pigment production which could, however, be restored by tyrosine,
thus indicating that synthesis of melanin by embryonic chick melanoblasts is inhibited by phenylalanine.
Kruse and White (1961) have studied changes in protein content
during the growth cycle of primary cultures of mammalian cells
obtained from two different tumours. The protein-nitrogen content
per cell decreased in the lag phase that occurred during the initial
period of cultivation, and then subsequently increased to a higher and
approximately constant value in the logarithmic phase of growth.
These results were in contrast to those obtained by other workers in
experiments with several established cell lines in which an increase of
protein occurred in the lag phase, followed by a decrease during the
logarithmic phase.
Tissue-Culture techniques can be combined with methods in which
sub-cellular particles are used in studies on the mechanism of protein
synthesis. Cell fractionation studies have been made on cultures of
osteoblasts which were grown in the presence of labelled proline and
then homogenized prior to differential centrifugation in sucrose
solution (Jackson, 1958, 1960). The object of these experiments
was to find whether the site of incorporation of free proline into the
proteins of the cell was the same as that of the formation of the protein-