364
the slow accumulation of point mutations observed with globular proteins,” (Sage and
Gray 1977 ). Faury ( 2001 ) gives more detailed explanation:
“Evolution of species has led to the appearance of circulatory systems. These include blood
vessels and one or more pulsatile pumps, typically resulting in a low-pressurised open circulation in most invertebrates and a high-pressurised closed circulation in vertebrates. In
both open and closed circulations, the large elastic arteries proximal to the heart damp out
the pulsatile fl ow and blood pressure delivered by the heart, in order to limit distal shear
stress and to allow regular irrigation of downstream organs.
To achieve this goal, networks of resilient and stiff proteins adapted to each situation –
i.e. low or high blood pressure -have been developed in the arterial wall to provide it with
non-linear elasticity. In the low-pressurised circulation of some invertebrates, the mechanical properties of arteries can almost be entirely microfi bril-based. In high-pressurised circulations, they are due to an interplay between a highly resilient protein, an elastomer in the
octopus and elastin in most vertebrates, and the rather stiff protein collagen.
In vertebrate development, elastin is incorporated in elastic fi bres, on pre-deposited
scaffold of microfi brils. The elastic fi bres are then arranged in functional concentric elastic
lamellae and, with the smooth muscle cells, lamellar units. The microfi brils may also play
a direct functional role in all mature arteries of high- and low-pressurised circulations.
Finally, blood pressure regularly increases with developmental stages it appears possible
that the early deposition of microfi brils, which are highly-conserved in evolution, corresponds at least in part, to an early microfi bril-driven elasticity in low-pressurised arteries,
present across species. In vertebrates, when pressure developmentally rises above a threshold value, the vascular wall stress may turn on the expression of other resilient protein
genes, including the elastin gene. Elastin would then be deposited on microfi brils, resulting
in the elastic fi bre network and elastic lamellae whose mechanical properties are adapted to
allow for proper arterial work at higher pressures,” (Faury 2001 ).
Therefore, below, I would like to discuss in particular data reported on the elastin
properties of arteries in marine fi sh and mammals, including cetaceans. Intriguingly,
elastin-based arteria of giant whale species are examples of the largest elastincontaining blood vessels known in Nature. In these large marine species, “this
rubber- like protein forms a highly extensible tissue that has an elastic modulus of
approximately 1 MPa, comparable with that of an ordinary rubber band,” (Shadwick
1999 ; see also Aaron and Gosline 1980 ).
10.1 Elastin-Like Proteins in Lamprey
In contrast to gnathostomes with cartilage of fi brillar collagen origin, the same tissue in lampreys possesses elastin-like proteins as the dominant matrix components
(Wright et al. 1988 ). So called lamprin has been identifi ed as example of the elastinlike protein of lamprey trabecular cartilage (Robson et al. 1993 ; McBurney et al.
1996 ), although that of the pharyngeal cartilage has not been characterized (Robson
et al. 1997 ). There are some elastin-like sequences reported for defi nitively noncollagenous lamprin (Robson et al. 2000 ). For example, the repetitive sequence
GGLGY that was found in lamprin, appear also in other proteins, i.e. elastin, spidroin, spider minor ampullate silk proteins, in matrix proteins of the chorion, or the
egg shell membrane of insects (Bochicchio et al. 2001 ).
10 Marine Elastin
the slow accumulation of point mutations observed with globular proteins,” (Sage and
Gray 1977 ). Faury ( 2001 ) gives more detailed explanation:
“Evolution of species has led to the appearance of circulatory systems. These include blood
vessels and one or more pulsatile pumps, typically resulting in a low-pressurised open circulation in most invertebrates and a high-pressurised closed circulation in vertebrates. In
both open and closed circulations, the large elastic arteries proximal to the heart damp out
the pulsatile fl ow and blood pressure delivered by the heart, in order to limit distal shear
stress and to allow regular irrigation of downstream organs.
To achieve this goal, networks of resilient and stiff proteins adapted to each situation –
i.e. low or high blood pressure -have been developed in the arterial wall to provide it with
non-linear elasticity. In the low-pressurised circulation of some invertebrates, the mechanical properties of arteries can almost be entirely microfi bril-based. In high-pressurised circulations, they are due to an interplay between a highly resilient protein, an elastomer in the
octopus and elastin in most vertebrates, and the rather stiff protein collagen.
In vertebrate development, elastin is incorporated in elastic fi bres, on pre-deposited
scaffold of microfi brils. The elastic fi bres are then arranged in functional concentric elastic
lamellae and, with the smooth muscle cells, lamellar units. The microfi brils may also play
a direct functional role in all mature arteries of high- and low-pressurised circulations.
Finally, blood pressure regularly increases with developmental stages it appears possible
that the early deposition of microfi brils, which are highly-conserved in evolution, corresponds at least in part, to an early microfi bril-driven elasticity in low-pressurised arteries,
present across species. In vertebrates, when pressure developmentally rises above a threshold value, the vascular wall stress may turn on the expression of other resilient protein
genes, including the elastin gene. Elastin would then be deposited on microfi brils, resulting
in the elastic fi bre network and elastic lamellae whose mechanical properties are adapted to
allow for proper arterial work at higher pressures,” (Faury 2001 ).
Therefore, below, I would like to discuss in particular data reported on the elastin
properties of arteries in marine fi sh and mammals, including cetaceans. Intriguingly,
elastin-based arteria of giant whale species are examples of the largest elastincontaining blood vessels known in Nature. In these large marine species, “this
rubber- like protein forms a highly extensible tissue that has an elastic modulus of
approximately 1 MPa, comparable with that of an ordinary rubber band,” (Shadwick
1999 ; see also Aaron and Gosline 1980 ).
10.1 Elastin-Like Proteins in Lamprey
In contrast to gnathostomes with cartilage of fi brillar collagen origin, the same tissue in lampreys possesses elastin-like proteins as the dominant matrix components
(Wright et al. 1988 ). So called lamprin has been identifi ed as example of the elastinlike protein of lamprey trabecular cartilage (Robson et al. 1993 ; McBurney et al.
1996 ), although that of the pharyngeal cartilage has not been characterized (Robson
et al. 1997 ). There are some elastin-like sequences reported for defi nitively noncollagenous lamprin (Robson et al. 2000 ). For example, the repetitive sequence
GGLGY that was found in lamprin, appear also in other proteins, i.e. elastin, spidroin, spider minor ampullate silk proteins, in matrix proteins of the chorion, or the
egg shell membrane of insects (Bochicchio et al. 2001 ).
10 Marine Elastin