A more detailed understanding of the immune mechanisms involved in anti-inflammatory events in fish is required for effective disease control in aquaculture. Significant expansion of immune genes, often resulting from whole genome duplication events in teleost fish, adds complexity to their potentially anti-inflammatory pathways. This thesis contributes to a more complete insight into the suppressor of cytokine signalling (SOCS) and transforming growth factor-β1 (TGF-β1) gene system in fish by the discovery of paralogues and reporting of ways in which these potential negative regulators of immune responses can be induced in the the commercially valuable rainbow trout (Oncorhynchus mykiss). Gene expression analysis, revealed that a novel trout TGF-β1 paralogue (TGF-β1b) was more inducible by immune stimulants than the known TGF-β1a and likely represents an important intrinsic factor in macrophages. Both trout TGF-β type I and type II receptor (TGFBR1 and TGFBR2) genes identified encode highly conserved serine/threonine kinases and they are modulated during immune responses. Counter-regulation of the two receptor transcripts in immune stimulated macrophages may indicate regulatory mechanisms operating at the receptor level. Thorough phylogenetic and synteny analysis of the lower vertebrate SOCS system led to further paralogue discovery and uncovered that the proposed teleost-specific SOCS-8 and SOCS-9 members are more likely paralogues of cytokine inducible SH2-containing protein (CISH) and SOCS-5. The trout SOCS-2 subfamily was expanded to three members by cloning SOCS-2b and SOCS-2bRel in addition to SOCS-2a. I revealed for the first time that four paralogues in a SOCS subfamily exist in a teleost by cloning trout CISHa2, CISHb1 and CISHb2 in addition to the known CISHa1. In vivo and in vitro expression of the CISH paralogues suggest possible subfunctionalisation in immunity and development. Attempts to produce trout recombinant proteins of potentially anti-inflammatory cytokines in transiently transfected mammalian cells primed exploitation of these molecules in functional studies.

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published_or_final_version / Physiology / Master / Master of Philosophy

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When a formant transition (isolated transition) and the remainder (base) of a synthesized syllable are presented to opposite ears most subjects perceive two simultaneous sounds, a syllable and a nonspeech chirp. The isolated transition determines the identity of the syllable at one ear and, at the same time, is perceived as a chirp at the opposite ear. This phenomenon, called duplex perception, has been interpreted as the result of the independent operation of two perceptual modes, the phonetic and the auditory mode. In order to test this hypothesis, the isolated transition was preceded and followed by a series of identical transitions sent to the same ear. This streaming procedure weakened the contribution of the transition to the perceived phonetic identity of the syllable. This weakening effect could have been explained in terms of the habituation of an hypothetical phonetic feature detector sensitive to the repetition of identical transitions. For this reason, the same effect was replicated by capturing the isolated transition with others which were aligned on the same frequency-by-time trajectory as the isolated one. These findings are consistent with the idea that the integration of the transition with the base was affected by the operation of general-purpose auditory processes. This contrasts with the hypothesis that the phonetic mode integrated the dichotic stimuli independently of the auditory mode.

Estes (l962) has stated that there may be as many outcomes in the evaluation of a learning experiment as there are changes in performance. Since performance is the basic datum from which learning is inferred, the question arises as to when a performance measure ceases to reflect performance, per se, and when it begins to reflect learning. This thesis is concerned with the above problem as it relates to one form of simple learning, viz., classical conditioning, and one response system, namely the galvanic skin response (GSR). The assessment of learning through classical conditioning of the GSR involves three related issues. [...]