Several experiments were performed to determine the effect of confinement stress,
Cortisol, and pulp mill effluent on phagocyte function in juvenile salmonids. Phagocytosis
and superoxide production of anterior kidney phagocytes as well as plasma Cortisol and
plasma glucose concentrations were measured. Five different confinement experiments
and a disease challenge were performed, but only a combination of confinement and
increased temperature resulted in a decrease in phagocytosis at 3 d. However, superoxide
production was increased at the same time and at two other times in separate experiments.
In a disease challenge experiment, confinement had no effect on mortality due to
vibriosis, however, mortalities due to an opportunistic infection of tail rot were
significantly higher in unconfined, sham-challenged fish suggesting that in this case
confinement was protective. Plasma glucose concentration was also significantly elevated
in unconfined, sham-challenged fish 2 d post challenge while plasma Cortisol
concentration was elevated in both confined and unconfined disease-challenged fish.
Phagocytosis was increased in unconfined disease-challenged fish at 2 d post challenge
while superoxide production was increased in both confined and unconfined sham-challenged
fish. These results indicate that the relationship between stress, immune
function, and disease resistance is complex, and requires the measurement of many
aspects of immune function.
Injection of a Cortisol analog (prednisolone) and implantation of Cortisol into coho
salmon (Oncorhynchus kisutch) resulted in decreased phagocytosis. Cortisol implantation
in chinook salmon (O. tshawytscha), however, resulted in increased phagocytosis and had
no effect on superoxide production. Cortisol had no effect on phagocytosis or superoxide
production in vitro at a physiological concentration, however, phagocytes incubated in
vitro with 10% pooled serum from fish stressed for 1 h or 3 d resulted in a significant
reduction in phagocytosis and an increase in superoxide production compared to
phagocytes incubated with serum from control fish. This combined with the Cortisol
results from the confinement experiments indicate that the effect of Cortisol is not direct
and that plasma Cortisol concentration is not a good predictor of phagocyte function.
Pulp mill effluent caused significant increases in superoxide production and
decreases in phagocytosis especially at low concentrations. Hypoxia also caused an
increase in superoxide production, but had no effect on phagocytosis.
It was concluded that stress and Cortisol do not have a general suppressive effect
on immune function. Some aspects of immune function may be suppressed while others
are stimulated to compensate. Pulp mill effluent exposure had a significant effect on
phagocyte function, and like stress and Cortisol, both suppressive and stimulatory effects
were observed. / Land and Food Systems, Faculty of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/6031 |
| Date | 11 1900 |
| Creators | Pegg, James R. |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 3683976 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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