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Studies on the granulocyte cell surface oxidase.

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Dewar, Catharine Lynne (1979) Studies on the granulocyte cell surface oxidase. PhD thesis, University of Tasmania.

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Abstract

This thesis examined the possible role of the microfilaments and
microtubules in controlling the activity of the granulocyte plasma membrane
oxidase. There have not been any detailed investigations of this topic
published to date.
The conflicting literature on the nucleotide specificity and
location of the oxidase within the granulocyte was examined. In vitro
techniques for isolating granulocytes from human peripheral blood and for
quantitating the initial rate of plasma membrane oxidase activity were developed
and used for these investigations. The involvement of microfilaments
and microtubules in oxidase activity was studied by using pharmacological
agents known to disrupt these structures in vitro (cytochalasin B, and
colchicine, vinblastine and vincristine, respectively). Control experiments
were also performed to ensure that microfilament and microtubule disruption
by these agents provided the best explanation for the results presented herein.
Correlative experiments were conducted to determine if a change in
hexose monophosphate shunt activity was associated with the observed
changes in plasma membrane oxidase activity brought about by the drug
treatments.
Experiments on non-phagocytic granulocytes showed that microfilament
disruption led to enhanced oxidase activity, while microtubule disruption produced
a dual effect : a paradoxical enhancement (with low doses or brief
exposures to the agents) and an impairment in oxidase activity. These
results suggested that microfilaments act as a constraint against, while
microtubules are required for plasma membrane oxidase activity. The requirement
for microtubules was highlighted in experiments where the usual
enhancement in oxidase activity with cytochalasin B was ablated when the
granulocytes were concomitantly incubated with a microtubule-disrupting
agent. (With phagocytic granulocytes qualitatively similar results were
observed. However, those experiments were not suitable for studying cell
surface oxidase activity because the presence of ingestable. Particles made
it impossible to determine whether plasma membrane and/or granule oxidase
activity was being measured.)
Based on the spectrophotometric and electron microscopic results
presented and the relevant findings from other investigators, a scheme
concerning the participation of the cytoskeletal elements in granulocyte
plasma membrane oxidase activity was devised. In this scheme the microfilaments
physically constrain the oxidase within the plasma membrane,
and thereby hold the activity of the oxidase in check. Thus, microfilament
disruption is envisaged to result in enhanced oxidase activity by freeing the
enzyme. However, the oxidase is viewed as optimally active only as long as
the microtubules are present to maintain the plasma membrane topography
suitable for the enzyme's activity.

Item Type: Thesis (PhD)
Keywords: Granulocytes, Cell membranes, Oxidases, Microtubules
Copyright Holders: The Author
Copyright Information:

Copyright 1979 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1981. Bibliography: l. 184-202

Date Deposited: 08 Dec 2014 23:54
Last Modified: 19 Jul 2016 23:58
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