2 Basic Information and Overview
19
unless sterols are provided. Insects cannot synthesize sterols, but some
insect cell lines can proliferate in a lipid-free medium (Mitsuhashi et aI.,
1983). Therefore, sterols are not essential, at least for some insect cell
lines.
Insect cells seem to synthesize very small amounts of linoleic acid
and linolenic acid, or cannot synthesize them. However, some insect cell
lines can multiply in lipid-free medium. Other fatty acids, neutral lipids,
and phospholipids are not essential for the multiplication of insect cells.
Other than amino acids, several organic acids that are mostly substrates
of the enzymes of the tricarboxylic acid (TeA) cycle have been incorporated in insect cell culture media. Since Wyatt (1956) first used four organic acids in her medium, organic acids are commonly used in culture
media and include malic acid, fumaric acid, u-ketoglutaric acid, and succinic acid. The organic acids may have growth-promoting ability; however, they are not essential for the multiplication of insect cells.
Various protein products, such as peptone, bovine plasma albumin, and
tryptose phosphate broth, fetuin, and transferrin, have been used in insect cell culture media. However, they are all non -essential, although some
show a growth-promoting action.
Protein hydrolysates are often used as sources of amino acids. The
most frequently used is lactalbumin hydrolysate. The digests of egg albumin, bovine fibrin, milk casein, and liver are sometimes used. They
contain peptides of various sizes in addition to free amino acids. They
also contain many unknown substances.
Some insect cell culture media contain bases and sugars that constitute
nucleic acids. However, they are not essential. Of these nucleic acid-related compounds, hypoxanthine is used frequently.
Insect hormones, such as ecdysone, juvenile hormone, and
prothoracicotropic hormone, are reportedly growth stimulating. However, none is essential for cell growth. In vertebrate cell culture, insulin is
known as a growth factor, but it has no effect on insect cell growth, except in cultures of Drosophila melanogaster cells.
Insect hemolymph is an additive used widely in insect cell culture media. Most insect cells require insect hemolymph or fetal bovine serum
(FBS) as an additive in synthetic media. The insect hemolymph should
contain some growth factor(s). Notwithstanding the many attempts to
clarify this growth factor(s), the active substance(s) in hemolymph has
not been isolated. Usually, the growth-promoting action of insect
hemolymph is not species specific. In general, the blood of invertebrates
is used for the culture of their tissues or cells commonly.
Of the vertebrate sera used for insect cell culture, FBS is the most effective. The FBS should contain growth-promoting substance(s). Like inOrganic
acids
Proteins
and
peptides
Nucleic acidrelated
compounds
Hormones
Hemolymph
Vertebrate
sera
19
unless sterols are provided. Insects cannot synthesize sterols, but some
insect cell lines can proliferate in a lipid-free medium (Mitsuhashi et aI.,
1983). Therefore, sterols are not essential, at least for some insect cell
lines.
Insect cells seem to synthesize very small amounts of linoleic acid
and linolenic acid, or cannot synthesize them. However, some insect cell
lines can multiply in lipid-free medium. Other fatty acids, neutral lipids,
and phospholipids are not essential for the multiplication of insect cells.
Other than amino acids, several organic acids that are mostly substrates
of the enzymes of the tricarboxylic acid (TeA) cycle have been incorporated in insect cell culture media. Since Wyatt (1956) first used four organic acids in her medium, organic acids are commonly used in culture
media and include malic acid, fumaric acid, u-ketoglutaric acid, and succinic acid. The organic acids may have growth-promoting ability; however, they are not essential for the multiplication of insect cells.
Various protein products, such as peptone, bovine plasma albumin, and
tryptose phosphate broth, fetuin, and transferrin, have been used in insect cell culture media. However, they are all non -essential, although some
show a growth-promoting action.
Protein hydrolysates are often used as sources of amino acids. The
most frequently used is lactalbumin hydrolysate. The digests of egg albumin, bovine fibrin, milk casein, and liver are sometimes used. They
contain peptides of various sizes in addition to free amino acids. They
also contain many unknown substances.
Some insect cell culture media contain bases and sugars that constitute
nucleic acids. However, they are not essential. Of these nucleic acid-related compounds, hypoxanthine is used frequently.
Insect hormones, such as ecdysone, juvenile hormone, and
prothoracicotropic hormone, are reportedly growth stimulating. However, none is essential for cell growth. In vertebrate cell culture, insulin is
known as a growth factor, but it has no effect on insect cell growth, except in cultures of Drosophila melanogaster cells.
Insect hemolymph is an additive used widely in insect cell culture media. Most insect cells require insect hemolymph or fetal bovine serum
(FBS) as an additive in synthetic media. The insect hemolymph should
contain some growth factor(s). Notwithstanding the many attempts to
clarify this growth factor(s), the active substance(s) in hemolymph has
not been isolated. Usually, the growth-promoting action of insect
hemolymph is not species specific. In general, the blood of invertebrates
is used for the culture of their tissues or cells commonly.
Of the vertebrate sera used for insect cell culture, FBS is the most effective. The FBS should contain growth-promoting substance(s). Like inOrganic
acids
Proteins
and
peptides
Nucleic acidrelated
compounds
Hormones
Hemolymph
Vertebrate
sera