2 Basic Information and Overview
17
than twofold of the regular medium.
Some insect cell culture media contain so-called micro elements or
trace metals. Usually Fe, Cu, Mn, Co, Zn and Mo are used. The necessity
of these metals in the culture medium has not been studied well. Usually,
these metals are used at a concentration of 10-7 M, which is comparable
to the vitamin concentration commonly used. It may be difficult to avoid
contamination of these metals as impurities of other components of the
medium, and this makes elucidation of their necessity to the culture difficult. It has been reported that AICl 3 and ZnS0 4 ·7H 2 0 enhance the cellular adhesiveness and growth in culture of the fall armyworm Spodoptera
frugiperda cell line (Weiss et aI., 1980). The effect of Se, which has been
used in mammalian cell cultures sometimes, on the growth of insect cells
is not known.
Carbohydrates are important as a source of energy. Most carbohydrates Sugars
are digested to glucose and this is then taken up by cells. Glucose can be
used as the sole sugar source, although fructose, maltose, trehalose, mannose, and sucrose can also be utilized (Mitsuhashi, 1989). Many investigators believe that insect cells, like vertebrate cells, cannot consume sucrose; however, some cell lines can definitely consume sucrose. Grace
and Brzostowski (1966) have reported that cells from the emperor gum
moth Antheraea eucalypti consumed 23% of the sucrose in the medium.
Some cell lines can be cultured in a medium containing sucrose as the
sole carbohydrate (Mitsuhashi, 1987). It is known that some insect cells
liberate a-glucosidase into the culture media, and this seems to convert
sucrose to glucose and fructose (Kimura and Mitsuhashi, 1983). The ability to consume sucrose may depend on the production of a-glucosidase
by the cells. Sucrose is sometimes used to control the osmotic pressure
of the media (Grace, 1962). Trehalose is the main blood sugar of insects,
and can be taken up by cells. However, in general, incorporation of trehalose does not bring any benefits to the cells over the incorporation of
glucose.
Amino acids are necessary as a source of nitrogen. Since Wyatt (1956) Amino
formulated a mixture of free amino acids based on chemical analyses of acids
several insect hemolymphs, many investigators have adopted the same
amino acid composition for their media. These amino acids are 20 protein-constituting amino acids and ~-alanine. ~-Alanine has been incorporated into the culture media because insect hemolymph contains significant amounts of ~-alanine. By investigating the amino acid requirements of cultured insect cells, it is now evident that approximately 15
amino acids are essential. Most insect cells do not require a-alanine, ~alanine, aspartic acid, asparagine, glutamic acid, and, in the case of some
cell lines, glycine. The precise amino acid requirements fluctuate somewhat according to the cell line used. In general, the essential amino acids
are arginine, cystine, glutamine, glycine, histidine, isoleucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine
and valine (Mitsuhashi, 1980). It is believed that only the L-isomer of
17
than twofold of the regular medium.
Some insect cell culture media contain so-called micro elements or
trace metals. Usually Fe, Cu, Mn, Co, Zn and Mo are used. The necessity
of these metals in the culture medium has not been studied well. Usually,
these metals are used at a concentration of 10-7 M, which is comparable
to the vitamin concentration commonly used. It may be difficult to avoid
contamination of these metals as impurities of other components of the
medium, and this makes elucidation of their necessity to the culture difficult. It has been reported that AICl 3 and ZnS0 4 ·7H 2 0 enhance the cellular adhesiveness and growth in culture of the fall armyworm Spodoptera
frugiperda cell line (Weiss et aI., 1980). The effect of Se, which has been
used in mammalian cell cultures sometimes, on the growth of insect cells
is not known.
Carbohydrates are important as a source of energy. Most carbohydrates Sugars
are digested to glucose and this is then taken up by cells. Glucose can be
used as the sole sugar source, although fructose, maltose, trehalose, mannose, and sucrose can also be utilized (Mitsuhashi, 1989). Many investigators believe that insect cells, like vertebrate cells, cannot consume sucrose; however, some cell lines can definitely consume sucrose. Grace
and Brzostowski (1966) have reported that cells from the emperor gum
moth Antheraea eucalypti consumed 23% of the sucrose in the medium.
Some cell lines can be cultured in a medium containing sucrose as the
sole carbohydrate (Mitsuhashi, 1987). It is known that some insect cells
liberate a-glucosidase into the culture media, and this seems to convert
sucrose to glucose and fructose (Kimura and Mitsuhashi, 1983). The ability to consume sucrose may depend on the production of a-glucosidase
by the cells. Sucrose is sometimes used to control the osmotic pressure
of the media (Grace, 1962). Trehalose is the main blood sugar of insects,
and can be taken up by cells. However, in general, incorporation of trehalose does not bring any benefits to the cells over the incorporation of
glucose.
Amino acids are necessary as a source of nitrogen. Since Wyatt (1956) Amino
formulated a mixture of free amino acids based on chemical analyses of acids
several insect hemolymphs, many investigators have adopted the same
amino acid composition for their media. These amino acids are 20 protein-constituting amino acids and ~-alanine. ~-Alanine has been incorporated into the culture media because insect hemolymph contains significant amounts of ~-alanine. By investigating the amino acid requirements of cultured insect cells, it is now evident that approximately 15
amino acids are essential. Most insect cells do not require a-alanine, ~alanine, aspartic acid, asparagine, glutamic acid, and, in the case of some
cell lines, glycine. The precise amino acid requirements fluctuate somewhat according to the cell line used. In general, the essential amino acids
are arginine, cystine, glutamine, glycine, histidine, isoleucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine
and valine (Mitsuhashi, 1980). It is believed that only the L-isomer of