2 . M E T H O D S
27
to cells of the ionic balance in their surroundings, nor does the delicacy
of its control in the body suggest that it can be treated lightly in Tissue
Culture.
The specific roles of calcium in bone and tooth formation in vitro
and in the binding of epithelial cells into sheets have been well recognized, but there are few other studies in which the effects of varying
the concentration of this ion on cells in Tissue Culture have been
systematically investigated. In some tissue cultures (e.g. chick fibroblasts in Tyrode's solution with fowl plasma) precipitation of calcium
salts readily occurs in the vicinity of the tissues when the p H is not
controlled.
G. E N E R G Y SOURCE
In the construction of most artificial culture media a source of
energy is usually included. Naturally this tends to take the form of a
concentration of glucose equivalent to that found in the blood of the
animal from which the tissues are taken and it should be noted that
this concentration varies over quite wide limits from species to species
(e.g. rat and hen 200 mg/100 ml; man 100 mg/100 ml). However, since
the concentration of glucose in a culture medium must depend both
on its initial value and on the rate at which the sugar is used up, which
in turn depends on the type and size of culture and the initial volume
of fluid, the optimum concentration in the initial medium may have
to be determined ad hoc. Most cells will tolerate much higher concentrations than they normally have in their surroundings. Cultures of
epithelial cells in general, and particularly of epidermis (Parshley
and Simms, 1950), benefit from large concentrations of glucose and so
also do those of neural tissues (Vol. 2, Chapter 9). Further discussions
of the food supplies for cultures will be found in the chapter on synthetic
media (Chapter 3), in the special chapters on metabolism (Chapters 811), and often in connexion with the culture of specific tissues.
H. T E M P E R A T U R E
The study of the optimal temperature at which cells should be
kept is again only in its infancy and is a complex problem. Not much
damage is normally done by maintaining the cells at the body temperature of the animal from which they are derived, and this is the usual
practice, but the growth of cells is sometimes greater, or survival
longer at temperatures slightly lower than this.
T o alter the temperature of a biological system where numerous
enzymic and metabolic processes with definite and perhaps different
temperature optima are normally working harmoniously together,
27
to cells of the ionic balance in their surroundings, nor does the delicacy
of its control in the body suggest that it can be treated lightly in Tissue
Culture.
The specific roles of calcium in bone and tooth formation in vitro
and in the binding of epithelial cells into sheets have been well recognized, but there are few other studies in which the effects of varying
the concentration of this ion on cells in Tissue Culture have been
systematically investigated. In some tissue cultures (e.g. chick fibroblasts in Tyrode's solution with fowl plasma) precipitation of calcium
salts readily occurs in the vicinity of the tissues when the p H is not
controlled.
G. E N E R G Y SOURCE
In the construction of most artificial culture media a source of
energy is usually included. Naturally this tends to take the form of a
concentration of glucose equivalent to that found in the blood of the
animal from which the tissues are taken and it should be noted that
this concentration varies over quite wide limits from species to species
(e.g. rat and hen 200 mg/100 ml; man 100 mg/100 ml). However, since
the concentration of glucose in a culture medium must depend both
on its initial value and on the rate at which the sugar is used up, which
in turn depends on the type and size of culture and the initial volume
of fluid, the optimum concentration in the initial medium may have
to be determined ad hoc. Most cells will tolerate much higher concentrations than they normally have in their surroundings. Cultures of
epithelial cells in general, and particularly of epidermis (Parshley
and Simms, 1950), benefit from large concentrations of glucose and so
also do those of neural tissues (Vol. 2, Chapter 9). Further discussions
of the food supplies for cultures will be found in the chapter on synthetic
media (Chapter 3), in the special chapters on metabolism (Chapters 811), and often in connexion with the culture of specific tissues.
H. T E M P E R A T U R E
The study of the optimal temperature at which cells should be
kept is again only in its infancy and is a complex problem. Not much
damage is normally done by maintaining the cells at the body temperature of the animal from which they are derived, and this is the usual
practice, but the growth of cells is sometimes greater, or survival
longer at temperatures slightly lower than this.
T o alter the temperature of a biological system where numerous
enzymic and metabolic processes with definite and perhaps different
temperature optima are normally working harmoniously together,