104
C H A R I T Y W A Y M O U T H
been consistent, but cells may differ widely in their dependence on,
or independence of, extraneous protein (Lucy, 1960; see also Chapter 9). It has long been known that cells grow better on some types
of glass than on others, and these differences show up more markedly
in protein-free media. The first cultures in completely defined media,
of embryonic chick cells, made by White (1946) were made directly
on glass. Those of Morgan, Morton and Parker (1950) were also, but
they at first adopted the method of supplying a protein-containing
feeding solution for the first 3-5 days, before the synthetic nutrient
was applied (Morton, Morgan and Parker, 1951). For a time, the
practice of using an inert substrate, e.g. perforated Cellophane (Evans
and Earle, 1947) was taken up, until it was found that certain cells
in biological fluid media could grow directly on glass. It was only a
short step further to the demonstration that some cells in defined media
could also adhere to glass, though with varying degrees of success.
Recently, since the development of satisfactory defined growth media,
and the decline in the practice of adding a small amount of serum,
studies of the conditions governing the attachment of cells to surfaces
have been made (Weiss, 1959a,b, 1961; Lieberman, Lamy and
Ove, 1959; Rappaport, Poole and Rappaport, 1960). Critical investigations of these matters had to await satisfactory protein-free
media, because protein monolayers on glass or other substrates, and
on the surface of the cells themselves, certainly create conditions
with respect to adhesion different from those where the surfaces are
not so coated. Most cells attach to protein-coated surfaces, as we must
suppose it is their natural habit to do in vivo, though it is also reported
that some cells attach and spread less readily on glass coated with proteins (the basic protamine, salmine, being an exception), than on
chemically-clean glass itself (Taylor, 1961, 1962; Holmes and Wolfe,
1961). Even in protein-free and chemically-defined media, studies of
surface interactions must take into account the fact that many cells
produce extracellular protein, which turns a protein-free medium
into a protein-containing one more or less rapidly. Rappaport, Poole
and Rappaport (1960), Rappaport (1960) and Rappaport and Bishop
(1960), on the hypothesis that protein plays an important role in surface
interactions, studied the characteristics of glass surfaces which would
permit adhesion and growth of cells in an initially protein-free system.
They postulate that such a system must (1) provide sufficient charge
per unit area of surface to permit cell attachment; (2) provide for
protection of the attachment sites from protons excreted by the cells
after attachment; and (3) provide an expanded surface matrix permitting diffusion at the cell-glass interface. High total negative charge,
and high Na content and proton-exchange capacity of the glass, were
C H A R I T Y W A Y M O U T H
been consistent, but cells may differ widely in their dependence on,
or independence of, extraneous protein (Lucy, 1960; see also Chapter 9). It has long been known that cells grow better on some types
of glass than on others, and these differences show up more markedly
in protein-free media. The first cultures in completely defined media,
of embryonic chick cells, made by White (1946) were made directly
on glass. Those of Morgan, Morton and Parker (1950) were also, but
they at first adopted the method of supplying a protein-containing
feeding solution for the first 3-5 days, before the synthetic nutrient
was applied (Morton, Morgan and Parker, 1951). For a time, the
practice of using an inert substrate, e.g. perforated Cellophane (Evans
and Earle, 1947) was taken up, until it was found that certain cells
in biological fluid media could grow directly on glass. It was only a
short step further to the demonstration that some cells in defined media
could also adhere to glass, though with varying degrees of success.
Recently, since the development of satisfactory defined growth media,
and the decline in the practice of adding a small amount of serum,
studies of the conditions governing the attachment of cells to surfaces
have been made (Weiss, 1959a,b, 1961; Lieberman, Lamy and
Ove, 1959; Rappaport, Poole and Rappaport, 1960). Critical investigations of these matters had to await satisfactory protein-free
media, because protein monolayers on glass or other substrates, and
on the surface of the cells themselves, certainly create conditions
with respect to adhesion different from those where the surfaces are
not so coated. Most cells attach to protein-coated surfaces, as we must
suppose it is their natural habit to do in vivo, though it is also reported
that some cells attach and spread less readily on glass coated with proteins (the basic protamine, salmine, being an exception), than on
chemically-clean glass itself (Taylor, 1961, 1962; Holmes and Wolfe,
1961). Even in protein-free and chemically-defined media, studies of
surface interactions must take into account the fact that many cells
produce extracellular protein, which turns a protein-free medium
into a protein-containing one more or less rapidly. Rappaport, Poole
and Rappaport (1960), Rappaport (1960) and Rappaport and Bishop
(1960), on the hypothesis that protein plays an important role in surface
interactions, studied the characteristics of glass surfaces which would
permit adhesion and growth of cells in an initially protein-free system.
They postulate that such a system must (1) provide sufficient charge
per unit area of surface to permit cell attachment; (2) provide for
protection of the attachment sites from protons excreted by the cells
after attachment; and (3) provide an expanded surface matrix permitting diffusion at the cell-glass interface. High total negative charge,
and high Na content and proton-exchange capacity of the glass, were