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Fish are subject to a variety of long and short term environmental and physical insults during their life; however they manage to adapt, ensuring physiological processes remain effective, enabling the animal to thrive in a wide range of conditions. One major environmental fluctuation that can occur rapidly or over a long period of time is temperature. Teleost fish, such as the rainbow trout (Oncorhynchus mykiss) are ectothermic, meaning their body temperature is regulated by environmental temperature which can affect activity levels, oxygen availability, biochemical reactions, biophysical processes, and importantly, circulatory demand and cardiac output.Rainbow trout heart is a relatively simple structure consisting of a single atrium and a single, double layered ventricle in an enclosed circulatory system. Cardiac output in the trout is largely intrinsically regulated in the short term by stretch, which modulates stroke volume.Long term acclimation or adaptation to cold temperature in trout has been previously shown to cause a type of cardiac remodelling, cardiac hypertrophy: an increase in muscle mass of the heart. The increase in muscle mass is thought to mitigate against the increase in blood viscosity in cold conditions.The aim of the present study was to further characterise this cardiac remodelling by using histological, immuno and genetic techniques to assess temperature dependent changes in the ventricle and atrium at the structural, proteomic and genetic levels, including defining the potential triggering events and mechanisms behind the changes. Trout were acclimated to three different temperatures. There was extensive temperature dependent, chamber specific remodelling of the muscle, connective tissue, and gap junction conduction channels. Atrial changes largely opposed ventricular responses. Cold acclimation was associated with spongy layer hypertrophy, increased collagen throughout, and atrophy of the atria. The reverse was true in warm acclimation. Genetic and proteomic analysis revealed there to be significant muscle (e.g. VMHC and MLP) and collagen (e.g. MMP13 and TIMP2) gene regulation coupled with temperature dependent changes in gap junction levels (e.g. Cx43 and Cx30.9) and distribution. Moreover, markers for stretch (e.g. ANP and BNP), stress (e.g. GR1 and DNAJ2) and neuro-hormonal input (e.g. Beta-AR2 and Beta-AR3b), coupled with significant cell signalling protein activation (e.g. p38MAPK and PKB) revealed extensive cardiac remodelling from trigger to output.Results from this study led to the conclusion that temperature acclimation causes extensive structural remodelling of the heart in order to satisfy the circulatory demand requirements of the animal in extremes of temperature. Cold fish are relatively inactive as shown by decreases in VEGF, and the heart remodels to pump blood around the body at low pressure, as shown by decreased compact layer thickness and atrophy of the atrium, and at low ejection volume, as shown by increases in stiffening collagen and spongy layer hypertrophy. A key trigger for the remodelling response is likely to be the degree of stretch the heart muscle is subject to, probably due to increased blood viscosity as shown by increases in stretch markers ANP and BNP in cold ventricle. To help ensure electrical harmony, gap junction remodelling occurs, as shown by significant changes in connexins in acclimated hearts. Due to structural observations and observed activation of signalling pathways such as GSK/PKB/NFAT, it was concluded that cardiac remodelling in rainbow trout shares similarities with physiological eccentric cardiac hypertrophy in mammals.

Although trigeminal ganglion morphogenesis has been intensively studied in birds, less is known about the molecular markers controlling mammalian cranial nerve development. A previously unsuspected role of the transcription factor Pax6 in regulating trigeminal neuronal precursor specification was investigated. Unlike in chick, Pax6 expression was observed in a subset of cells in the mouse developing trigeminal ganglion, overlapping both Pax3 expression, a specific marker of the ophthalmic placode (opV), and Islet1, the earliest neuronal marker for the maxillomandibular placode (mmV). The number of Islet1-positive cells at E9.5 in Pax6 mutants was significantly decreased, though the number of Pax3-positive cells was unaffected, suggesting a specific deficit in the specification of some of the sensory neuronal precursors. Analysis of nerve branching revealed abnormalities mainly within the maxillary division of the trigeminal nerve. In particular, Pax6 mutants have defects in the encirclement of the sensory axons around the whisker follicles, the major peripheral target of the maxillary branch. Neuropilin 1 expression was downregulated in the developing trigeminal ganglion in Pax6-null mutants. Furthermore we showed that perinatal expression of Pax6 is required for differentiation of Merkel cells, skin mechanoreceptors that in rodents represent the main peripheral target of the sensory free endings axons derived from the maxillary branch of the trigeminal nerve. Cytoplasmic localisation of Pax6 in developing Merkel cells was shown to be modulated by oxidative stress, as it is in the corneal epithelium. The data show that Pax6 has multiple roles at different levels of the whisker follicles somatosensory pathway controlling various aspects of this intensively studied neuronal circuit.

Limits to sustained energy intake during lactation were investigated in MF1 mice.  The feeding of high protein to females at 21°C had negative effects on lactation performance.  This was because the females consumed much less food and energy at peak lactation but their mean daily energy expenditure (DEE) was higher than that of females fed  high carbohydrate diet, so the energy available for milk production was greatly reduced. The feeding of high and medium fat diets to lactating females at 21°C had positive effects on lactation performance.  The females consumed much more food and energy at peak lactation but their mean DEE was the same as that of females fed low fat, so the energy available for milk production was greatly increased.  The positive effects of feeding high and medium fat to the lactating mice were far greater than predicted by the heat dissipation limit hypothesis, suggesting that this hypothesis can not explain all the findings of the present study.  The fixed DEE of  high fat, medium fat and low fat fed females strongly support the heat dissipation limit hypothesis. Lactation significantly decreased pro-opiomelanocortin (POMC) and increased agouti-related peptide (AgRP) gene expression in the hypothalamic arcuate nucleus (ARC) despite the reduced neuropeptide Y (NPY) expression in the ARC.  Activated AgRP orexigenic pathways and attenuated anorexigenic POMC pathways in the hypothalamus probably promoted the hyperplagia of lactation.  The fact that AgRP increased while POMC decreased but SOCS-3 was unchanged in the lactating females exposed to 21°C indicates that the MF1 mice were sensitive to the action of leptin.  mTOR was not involved in lactation hyperphagia in MF1 mice.  Lactation significantly increased fat mass and obesity-associated gene (FTO) expression in the hypothalamic ventromedial nucleus.  There were no changes in the main anabolic and catabolic neuropeptides at 30°C.

Many theories have emerged to explain how ageing and longevity are mediated.  Two theories are the ‘Rate of Living’ (ROL) theory (the live fast, die young concept) and the uncoupling to survive hypothesis.  The ROL theory postulates a positive link between energy expenditure and longevity whereas the uncoupling hypothesis predicts a negative association.  For a given mass, birds tend to live longer than mammals despite having higher energy expenditures. This study began by re-examining the relationship between body mass, energy expenditure and longevity in birds using published accounts of resting metabolic rate (RMR), daily energy expenditure (DEE) and maximum lifespan potential (MLSP). It was found that, after removing the confounding effects of body mass and phylogeny, RMR and DEE were not significantly related to MLSP.  There was also a significant negative association between lifetime RMR and DEE per gram, which contradicts the suggestion that this should be body mass independent.  The study then elucidated the age-related changes in energy expenditure in two long-lived companion birds, budgerigars (<i>Melopsittacus undulates</i>) and cockatiels (<i>Nymphicus hollandicus</i>).  Using indirect calorimetry to determine RMR and the doubly labelled water technique to estimate DEE, it was fond that these birds did not have age-related decreases in energy expenditure.  These two species, along with free-living fulmars (<i>Fulmarus glacialis</i>) do not have increased oxidative damage during ageing and no age-related changes in antioxidant protection.  It was also found that dietary fatty acids have no effect on oxidative damage but possibly influence antioxidant protection in fulmars.

The haemocytes of Patella were examined living and fixed and stained, by light microscopy and scanning electron microscopy. Similarities between haemocytes and vertebrate macrophages are probably a result of their similar functions, not of homology. The activity of the haemolymph was examined and found to contain no lytic factors or agglutinins to vertebrate red cells or to bacteria. A haemagglutinin-inhibition factor was found to be present, this inhibited the agglutination of human red blood cells (HRBC) by human anti-sera, but not that of sheep red cells by guinea-pig anti-sheep serum. Cultured in vitro, the haemocytes were found to lyse HRBC. This was quantified and found to be unaffected by prior opsonisation of the HRBC in Patella haemolymph. The haemocytes of pre-injected animals were found to be more avid. The haemocytes were able to phagocytose bacteria, when cultured with them in vitro. Opsonisation in haemolymph depressed bacterial uptake, but the haemolymph of pre-injected animals slightly enhanced uptake. Acid phosphatase was found to be naturally present in the haemocytes and haemolymph. Injection with bacteria resulted in elevated acid phosphatase levels and haemocyte numbers. Sea water injection did not cause elevation of haemocyte acid phosphatase or haemocyte number. Enhanced lysin synthesis is possibly a response to the foreign particles. Culture of haemocytes in vitro with bacteria did not cause detectable changes of acid phosphatase in the culture medium, although cellular levels changed. It is suggested that the haemocytes are not the primary source of this enzyme in the haemolymph. Since the haemolymph is not bactericidal it is suggested that haemolymph lysins may have an opsonic function. The results are discussed with reference to similar work which has been done on other molluscs.

Some aspects of the metabolism of Artemia have been investigated. Experiments have been made with animals of different stocks, obtained from different localities. The growth of Artemia is influenced not only by the sex of the animal, but also by the stock from which it is derived. Likewise, the effect of the salinity of the medium on growth varies with sex and stock. The growth of Artemia is retarded in brine with a low dissolved oxygen content. Changes in body proportions occur with increase in size of Artemia: in particular, the abdomen becomes relatively longer. Body form is also influenced by the salinity of the external medium. The extent to which this occurs varies with the sex of the animal and the stock from which it is derived. The oxygen consumption of Artemia has been measured in relation to the size and sex of the animal and also to the salinity of the medium and its dissolved oxygen content. Females have the same rate of oxygen uptake in sea water as in more concentrated brine. Malesin sea water have a higher rate of oxygen uptake than in concentratedbrine. This difference has been related to the greater area of the second antennae of males in sea water. The colours of Artemia are due mainly to haem compounds andcarotenoids. Haemoglobin occurs in solution in the blood; the role of this pigment in the life of Artemia has been investigated. The colours of the eggs are due to differences in total haem content of the egg shell. The red colour of the nauplius and of certain adults is due to carotenoids; some of these have been identified.

The integument of the minnow phoxinus phoxinus (L.) was studied using both light and electron microscopy and found to be similar in general structure to that of other teleosts. The various types of chromatophores and their location in the integument are described. In general, melanophores have well organized microtubule systems and their possible roles in the mechanism of pigment granule movement are discussed. Fine structural and histochemical studies of melanophores suggest that their innervation is single and is probably adrenergic. A continuous observation apparatus was employed to study in the living fish the responses to black and white background reversals of melanophores with intact innervation and of similar cells disconnected from the central nervous system by spinal nerve section. Results indicate that both pigment aggregation and pigment dispersion are active processes. Electrical stimulation of the spinal cord, which has been shown to result in pigment aggregation, evoked pigment dispersion in paled chromatically spinal fish pretreated with bretylium, an adrenergic neuron blocking agent. The effects of alpha- and beta-adrenoceptor agonists and antagonists on chromatically normal and chromatically spinal fish were studied. Noradrenaline, adrenaline (alpha agonists) and, in relatively higher concentrations, isoproterenol (a beta agonist) were found to be potent pigment-aggregating agents on melanophores of chromatically normal and chromatically spinal black-adapted fish. Neither isopro-terenol nor the more specific beta agonists fenoterol and isoxsuprine, injected in various concentrations were able to evoke pigment dispersion in chromatically normal white-adapted fish. However, they resulted in marked pigment dispersion (isoproterenol in relatively lower concentrations) in melanophores of chromatically spinal, prolonged white-adapted fish. It is generally concluded that the melanophores of the minnows have only an adrenergic innervation and that the mechanisms of pigment aggregation and pigment dispersion are mediated by alpha-and beta-adrenoceptors respectively. The effects of the incident light intensity on the rate and magnitude of the fish's response to black and white background reversals were also studied. The response of the fish was found to be constant over a wide range of incident light intensities. In the complete absence of light, or under very dim overhead illumination, melanophores in the lateral stripe showed some primary response. The fine structure of the minnow retina was studied. The various types of photoreceptor and their responses in different conditions of illumination are described.