Labelled metabolites in the study of immune expulsion of Nippostrongylus brasiliensis

MacLean, John MacPhee (1977) Labelled metabolites in the study of immune expulsion of Nippostrongylus brasiliensis. MSc(R) thesis, University of Glasgow.

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One of the features of Nippostrongylus brasiliensis infections in the rat is the sudden expulsion of the worm population commencing at about day 11 of infection, the rats subsequently being highly resistant to further infection. It has been known for some time that the parasites depend for their nutrition on the uptake of metabolites from the tissue fluids of the host. It was thought that measurements of the uptake of metabolites by the adult N. brasiliensis from the host's tissue fluids might provide an index of immunological damage sustained by the parasites. A method using metabolites trace labelled with radio-isotopes was employed. The substances used were 32P - sodium phosphate, 75Se- selenomethionine and 14C- glucose. The labelled materials were injected intravenously into the host and the levels of radioactivity in the worms at necropsy, five hours later, were ascertained. Such measurements do not of course represent "net" uptakes of labelled material but allow changes in the rate of transfer of labelled metabolites between the adult N. brasiliensis and the tissue fluids of the host to be measured. The relationship between these changes (or metabolite uptake), other changes known to occur in the parasites prior to their expulsion and the timing of the immune expulsion was examined. In the initial experiment described in Chapter I, it was observed that the rate of uptake of 32P from the host, following injection with 32P labelled phosphate, appeared to be related to the age of the infection, i.e. there was a greater uptake of 32P in a day 6 compared with a day 9 infection. Following this interesting observation the uptake of 32P by the parasites was measured between day 6 and 13 of Infection. After day 8 there was a rapid decline in the uptake of 32P by the worms, the significant point being that the decline in worm metabolic activity as measured in this way preceded worm expulsion by several days. It is known that worms transferred surgically to "clean" hosts on or before day 9 of infection are able to re-establish and continue normal reproductive activity but parasites transplanted after this time are less able to establish and resume normal functions. In order to investigate whether or not "transplanted" worms were able to recover their original capacity to take up metabolites a series of measurements were made in worms which had been surgically transferred to "clean" hosts between days 6 and 13 of infection. The results of this experiment indicated that worms transplanted after day 9 of infection were progressively less able to recover their ability to take up the labelled metabolite, presumably as a result of irreversible immune damage sustained in the first host. It is well established that if certain cortisone derivatives are administered to N. brasiliensis infected rats worm expulsion is prevented. When a series of measurements of uptake of 32P by parasites from host rats which had been injected with cortisone were made it was obvious that the ability of the worms to take up labelled metabolites was unimpaired, i.e. the reduced uptake of labelled metabolites observed in N. brasiliensis as an infection progresses appears to be related to the immune response of the host which also causes the expulsion of the parasites. In case the results obtained up to this point were peculiar to phosphate metabolism only, a series of measurements were carried out with a labelled amino acid (75Se- selenomethionine). The pattern of uptake of 75Se by the worms bore a remarkable similarity to that previously observed when 32P-sodium phosphate was used as the test metabolite. It seemed likely that the impairment in the uptake by the worms of both phosphate and amino acid, as an infection progressed, was related to developing immunity in the host. Chapter II described improvements in the procedures used for measuring the uptake of radioisotopically labelled metabolites by N. brasiliensis and the tests carried out to confirm the validity of the techniques. Using these improved methods, the uptake of metabolites by N. brasiliensis was measured in two experiments described in Chapter III. Where a mixture of 32P-sodium phosphate and 75Se-selenomethionine was injected into the host it was shown that the timing and magnitude of the depression of each metabolite was remarkably similar as immunity developed in a normal infection. The uptake of 14C-glucose was similarly measured and the pattern of 14C uptake observed corresponded closely to that seen when the uptakes of 32P or 75Se was measured. The results of these experiments confirmed that there was a dramatic fall in worm metabolic activity after day 8 of infection. (Abstract shortened by ProQuest.).

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Additional Information: Adviser: W Mulligan
Keywords: Parasitology
Date of Award: 1977
Depositing User: Enlighten Team
Unique ID: glathesis:1977-73130
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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