Biomedical Engineering Reference
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which he named 'hyalomucine', and which behaved differently from
the other mucoids in the cornea and in cartilage [6]. In 1934, Meyer
and Palmer isolated and identified a polysaccharide from the vitreous
body and named it HA [7]. It was first isolated as an acid, but under
physiological conditions it behaved like a salt (e.g., sodium salt of
the hyaluronate) [8].
Ac
H
H
OH
NH
COOH
OH
C
O
C
C
C
O
HO
O
O
HO
O
O
HO
HO
O
O
OH
NH
HOOC
OH
Ac
Figure 5.1
Chemical structure of HA
The term 'hyaluronan' was introduced in 1986 to conform to the
international nomenclature of polysaccharides and it is attributed to
Endre Balazs and co-workers [9], who coined it to encompass the
different forms of the molecule, e.g, the acid form such as HA, and the
salts, such as sodium hyaluronate, which forms at physiological pH.
HA can be found in all tissues and body fluids of vertebrates as
well as in some bacteria. Higher content of HA is found in the skin,
synovial fluid, umbilical cord, dermis, lung, brain, renal papillae and
the vitreous body of the eye [10-12]. It was estimated that in the
body of a person of 70 kg, about 15 g hyaluronan is found, of which
one third is turned over every day. The human skin contains over
50% of the hyaluronan in the body [5, 13]. Rooster combs contain
the highest concentrations of hyaluronan ever reported for animal
tissues (7.5 mg/g) [14]. Hyaluronan is also present in the capsule of a
small number of microbial pathogens such as
Pasteurella multocida
and group A and C streptococci among which are
Streptococcus
pyogenes
(a human pathogen) and the animal pathogens
S. equi
and
S. uberis
. These microorganisms use hyaluronan to encapsulate their
cells, forming a perfect disguise against the animal defence system and
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