Phillips, Angela (1985) Hymenolepis diminuta: monosaccharide absorption by the cysticercoid. Doctoral thesis, Keele University.

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Abstract

The cysticercoid of Hymenolepis diminuta was shown to absorb a limited number of monosaccharides by mediated transport. The monosaccharides transported were: glucose, galactose, mannose, l-deoxyglucose, 2-deoxyglucose, 2 deoxygalactose, 3-0-methylglucose and ~-methylglucoside. Other similar monosaccharides i.e. glucose analogues, were not absorbed and it was suggested that they do not possess the minimal structural requirements of actively absorbed compounds. Uptake studies on the recently excysted adult illustrated that it, too, absorbed the same limited range of monosaccharides as the cysticercoid. Extensive inhibition studies were performed, which demonstrated that all of the above mentioned monosaccharides were competitive inhibitors. The Ki value calculated for each hexose was very similar to its own Kt value for the uptake locus. From these data it was concluded that all the hexoses transported were absorbed via the same locus in cysticercoids and recently excysted adults. Hexose absorption in all cases involved a negligible diffusion component and glucose and galactose uptake was also inhibited by phlorizin, several metabolic inhibitors, but not ouabain. The absorption of glucose and galactose by cysticercoids and recently excysted adults was predominantly Na+-sensitive, although 70% of control uptake in cysticercoids and 30% in recently excysted adults took place in Na+-free media. It was assumed that this Na+-insensitive uptake was a function of the uptake locus and therefore probably also occurs in the absorption of the other transported hexoses not tested. The possibilty of two monosaccharide uptake loci in the cysticercoid and recently excysted adult- one Na+-sensitive, the other Na+-insensitive- was discussed. This study has highlighted differences in the uptake specificities and characteristics of the adult and cysticercoid monosaccharide absorption loci. The recently excysted adult was shown to posses 'intermediate' characteristics between those of the cysticercoid and lO day-old adult worm. The differences between adult and cysticercoid monosaccharide uptake loci are thought to reflect both the difference in carbohydrate requirement of cysticercoids and adults and also the availability of absorbable carbohydrate in their environments.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Natural Sciences > School of Life Sciences
Depositing User: Lisa Bailey
Date Deposited: 11 Dec 2019 10:17
Last Modified: 11 Dec 2019 10:17
URI: https://eprints.keele.ac.uk/id/eprint/7389

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