VITELLINE MEMBRANE AND CORTICAL PARTICLES 283
and a molar sucrose solution the eggs remained more spherical than the
nontreated eggs. The effect may also reside in the vitelline membrane,
which was not removed in these assays. It remains undecided as to
whether the inhibitors are able to penetrate also through the plasma
membrane into the inside region of the cortex. The ease with which the
inhibitors are removed by washing does not speak in favor of an intracortical penetration. Moreover, the inhibition of sperm attachment
is not an absolute one; rather, the inhibitors cause a considerate prolongation of the 50% fertilization time.
Fucoidin isolated from the alga Fucus vesiculosus
was tested with
respect to fertilization-impairing effect on eggs of Psammechinus
miliaris.
The result was negative. However, a fraction obtained as a byproduct
in the isolation procedure had a high inhibitory action. This fraction
was purified by Vasseur, and his work was continued by Esping (1957a).
A homogenous product was, however, never obtained. The "fertilization
inhibitor from Fucus" [Felnh(Fu)] has, however, been used by several
workers as a convenient inhibitor in the study of fertilization in sea
urchins (Harding, 1951; Wicklund, 1954a; Runnström and Hagström,
1955; Branham and Metz, 1960, 1962; see also the comprehensive review of fertilization inhibitors by Metz, 1961).
Β. Lindberg (1953) isolated a phenolic substance from Fucus. Wicklund found that this is also an active fertilization inhibitor. It is, therefore, tempting to believe that the active substance in Felnh(Fu) is the
phenolic substance of Lindberg. However, Wicklund (1954a) divided
the fertilization inhibitors examined by her into two different groups. The
first consisted of Felnh(Fu), human H substance, and chitindisulfuric
acid. The action of these is removed or decreased when periodate is
added to the test system. The hyaline layer brought into solution by
Nakano (1956) belongs to this group. The action of the second group of
substances (consisting of the phenolic substance from Fucus,
the
flavonols, germanin, homarine, and alloxan) was not removed by the
presence of periodate. Thus the phenolic substance and the Felnh(Fu)
belong to two different groups according to this classification. Besides
the phenolic substance there may be another more heparin-like substance present in Felnh(Fu). Its action and its partial removal by
periodate is illustrated in Fig. 26.
Branham and Metz (1960) made the interesting observation that pretreatment of the eggs with a rather high dose of trypsin renders the eggs
insensitive to a Felnh(Fu) prepared by them. This raises the question
of the site of action of this inhibitor. According to G. Lundblad
(1954) it inhibits the enzyme Ε 2 and shows, in this respect,
also a similarity to heparin. Trypsin pretreatment of the eggs in-
and a molar sucrose solution the eggs remained more spherical than the
nontreated eggs. The effect may also reside in the vitelline membrane,
which was not removed in these assays. It remains undecided as to
whether the inhibitors are able to penetrate also through the plasma
membrane into the inside region of the cortex. The ease with which the
inhibitors are removed by washing does not speak in favor of an intracortical penetration. Moreover, the inhibition of sperm attachment
is not an absolute one; rather, the inhibitors cause a considerate prolongation of the 50% fertilization time.
Fucoidin isolated from the alga Fucus vesiculosus
was tested with
respect to fertilization-impairing effect on eggs of Psammechinus
miliaris.
The result was negative. However, a fraction obtained as a byproduct
in the isolation procedure had a high inhibitory action. This fraction
was purified by Vasseur, and his work was continued by Esping (1957a).
A homogenous product was, however, never obtained. The "fertilization
inhibitor from Fucus" [Felnh(Fu)] has, however, been used by several
workers as a convenient inhibitor in the study of fertilization in sea
urchins (Harding, 1951; Wicklund, 1954a; Runnström and Hagström,
1955; Branham and Metz, 1960, 1962; see also the comprehensive review of fertilization inhibitors by Metz, 1961).
Β. Lindberg (1953) isolated a phenolic substance from Fucus. Wicklund found that this is also an active fertilization inhibitor. It is, therefore, tempting to believe that the active substance in Felnh(Fu) is the
phenolic substance of Lindberg. However, Wicklund (1954a) divided
the fertilization inhibitors examined by her into two different groups. The
first consisted of Felnh(Fu), human H substance, and chitindisulfuric
acid. The action of these is removed or decreased when periodate is
added to the test system. The hyaline layer brought into solution by
Nakano (1956) belongs to this group. The action of the second group of
substances (consisting of the phenolic substance from Fucus,
the
flavonols, germanin, homarine, and alloxan) was not removed by the
presence of periodate. Thus the phenolic substance and the Felnh(Fu)
belong to two different groups according to this classification. Besides
the phenolic substance there may be another more heparin-like substance present in Felnh(Fu). Its action and its partial removal by
periodate is illustrated in Fig. 26.
Branham and Metz (1960) made the interesting observation that pretreatment of the eggs with a rather high dose of trypsin renders the eggs
insensitive to a Felnh(Fu) prepared by them. This raises the question
of the site of action of this inhibitor. According to G. Lundblad
(1954) it inhibits the enzyme Ε 2 and shows, in this respect,
also a similarity to heparin. Trypsin pretreatment of the eggs in-