Investigations of the infection by schistosome parasites of their molluscan intermediate hosts
Targett, G. A;
(1961)
Investigations of the infection by schistosome parasites of their molluscan intermediate hosts.
PhD thesis, London School of Hygiene & Tropical Medicine.
DOI: https://doi.org/10.17037/PUBS.00682401
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The respiratory pigments
and
the
amino
acid
composition of planorbid
snails
which
act
as
intermediate hosts for
human
schistosomes
were
compared
with those of insusceptible snail
species.
The absorption spectra
of
haemoglobins from
different snail species were similar
to
one
another
and
closely related to those of mammalian
haemoglobins.
The occasional appearance
of
additional
absorption
bands
suggested that substances
other
than the
pigment
protein
appear infrequently in snail
blood.
Electrophoresis showed
that, in
general,
the
respiratory pigment was
the
only
protein
present
in the
blood. The mobility
of
haemoglobin
and
haemocyanin
pigments was not affected by
change
in
pH, and
the
rates
of movement of haemoglobins from twelve
different
snail
species were the same.
Other
proteins
occurred
occasionally
in the blood of most species examined,
and
these
additional
fractions seemed to form a
common pattern
in four
species.
The factors determining their
appearance
were
investigated.
No qualitative differences
were
observed
in the
amino acid content of haemoglobins from
different snails,
but quantitative differences were
demonstrated.
The free amino acids of snail
blood
were
in low
concentration but were qualitatively similar
in three
snail species, which also contained
similar
bound
and
free amino acids in the digestive
glands
and
ovotestes.
Australorbis glabratus,
however,
differed from
Planorbarius corneus and Lymnaea stagnalis
since
free
methionine was found in its
anterior
tissues.
The
methionine was not present
in
glabratus
snails
infected
with Schistosoma mansoni, and
they
contained
lower
concentrations of free amino
acids
than
uninfected
snails.
It was shown that methionine was
one
of
the
seventeen
amino acids identified in the
protein
of
S. mansoni cercariae.