Aspects carbohydrate metabolism in the plerocercoid of Schistocephalus solidus.
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Three spined sticklebacks infected with Schistocephalus solidus
plerocercoids were used for in-vivo experiments to determine the
relative distribution of 14C-labelled sugars (D-glucose and 3-0-M D-glucose) in fish and worm tissues.
A maximum of 23.6% labelled material from D-glucose was
found in plerocercoids after 4.5 hours and a maximum of 2.8%
labelled material from 3-0-M glucose after 24 hours. Comparison
of distribution levels between the two sugars and between infected
and uninfected fish tissues did not show significant differences
except in a few cases.
In-vitro studies with plerocercoids demonstrate D-glucose
uptake to be sodium dependent, saturable with an apparent Kt of
O.66mM, inversely related to dry weight and absorbed against a
concentration gradient. Uptake is also affected by temperature
with high rates at 200 and 400C and lower rates at 100 and 30°C.
Uptake is inhibited (non-competitively) by phlorizin and to
a lesser extent by ouabain and DNP. The nature of inhibition
caused by the latter two compounds was not determined.
THe effect of 3-O-M glucose on D-glucose uptake was
inconclusive. Similarly the effect of D-galactose was inconclusive
and also inconsistent,causing both stimulation and inhibition of
D-glucose uptake.
A gradient of glucose absorption is present along the length
of the plerocercoid; the lowest rate being found at the anterior
section and the highest at the posterior end.
Plerocercoids incubated under aerobic conditions in 14C-D-glucose
produced insignificant amounts of labelled CO2.
Under aerobic conditions lactate is produced by plerocercoids at
the rate of O.13mg/ml/hour but no detectable amounts of pyruvate
were found under similar conditions.
Glycogen extracts from plerocercoids incubated in-vivo
contain increasing levels of 14C-labelled material with increased
incubation periods.
Host metabolism is significantly affected by the presence
of plerocercoids. Lower levels of glycogen are found in the liver
tissue of infected fish compared to uninfected fish. Also the rate
of D-glucose uptake by fish stomach and intestinal tissues is
considerably reduced in infected fish.
Authors
Burns, MichaelCollections
- Theses [3834]