The distinct structure of the Central Complex (CC) spanning the midline is one of the most prominent features of the <i>Drosophila </i>brain. The CC is highly conserved across insect species and is involved in multimodal information processing and coordination of locomotion. By employing a combination of immunohistochemical techniques, enhancer trap technology and mutant analysis, this thesis has analysed the structural development of the CC. In this study the expression patterns from a subset of genes encoding Cell adhesion molecules generated three developmental series’ from which a development timeline for the CC was determined. The <i>echinoid </i>gene displayed elevated expression in the Horizontal fibre system allowing a detailed developmental characterisation of this set of isomorphic neurons. Further analysis using enhancer trap lines revealed genetic subdivision of neurons and isolation of isomorphic sets. These lines were subsequently used to assess the development of several identified CC neurons. These experiments determined CC development to be in the first 48-52 hours after puparium formation. The F<i>l</i> neurons and neurons of the Horizontal and Vertical fibre systems were established first followed by a second wave of outgrowth from Pontine, <i>fb-eb </i>and R neurons. This study infers details of gross CC structure indicated by projection patterns of neurons and mutant analysis. One of the genes involved in development, <i>echinoid, </i>is further analysed for a potential pathfinding function using the model of the Optic lobe. Finally, this thesis presents the advantages conferred by the use of enhancer trap lines for developmental study of the CC and has isolated a novel set of these lines that will be beneficial for future studies into both development and behaviour of the CC.

The intention of this work was to investigate the problems concerned with transferring rainbow trout 'Salmo gairdneri' directly from fresh water into sea water with reference to this procedure on a marine trout farm. A laboratory study of some of the physiological changes that occur following direct transfer of rainbow trout to sea water was undertaken. The effect of size and salinity on the osmoregulatory ability of the fish was investigated. Field trials involving sea cages were also performed with fish of different sizes and varying salinities. The results obtained from the field were used to produce a nomogram relating size and salinity with expected levels of mortality; this nomogram is thought to have considerable applications in the marine trout farming industry. The results from the field and the laboratory were compared and they indicated a considerable detrimental effect of prior transportation. Two methods for alleviating the osmotic shock following transfer were investigated in the hope of lowering mortalities. The first method investigated was the feeding of a wet diet containing 50% fresh water following transfer with the intention of reducing the dehydration and high plasma concentrations. This method was shown to be ineffective and possible reasons for this are discussed. The second method examined in an attempt to reduce mortalities was the prior feeding of a high salt diet. It was found that the feeding of a diet containing 10% NaCl for a period prior to seawater transfer significantly reduced mortalities during the first few days in the marine environment. The optimum period of prior feeding of the high salt diet was found to be about 2 weeks as longer periods did not improve the beneficial results and resulted in poorer growth rates. Those fish fed on the high salt diet were found to have significantly lower plasma osmotic concentrations following transfer and this finding is discussed in relation to known mechanisms of salt excretion. A study of the "chloride cells" in the gills was undertaken but no attributable effect was found following the feeding of the high salt diet.

Diseases of the digestive tract account for nearly half the deaths which occur in horses; despite this, very few investigations have been made into the functions of this system. The work described here was undertaken with the object of providing some information on this subject. It is hoped that the information obtained will be of value in understanding some of the pathalogical conditions and will also advance knowledge of digestion in herbivorous mammals. In this last respect, studies on the horse provide a useful comparison with those on the ruminant. Since the size and cost of horses made acute experiments impracticable, it was necessary to devise other methods of investigation. The supply of fresh intestines was available from horses slaughtered for food. This was utilized and a technioue developed for the perfusion of isolated segments of intestine (Alexander, 1949). The movements of the ileum and small colon were studied in this fashion and also the effect on them of various humoral agents. When the ileum was perfused with isotonic solutions containing oxygenated red blood cells, it showed propulsive movements. This was studied in more detail (Alexander, 1950) and it was found that the magnitude of the movements varied with the supply of oxygen. The effects of the inorganic constituents of the perfusion fluid were investigated and, of these, only sodium ions seemed to have a specific effect. During the course of these experiments a fast propelling mechanism was observed which propelled balloons through the ileum at rates of 1-4 cm./sec. This mechanism could be shown only in a small proportion of preparations and differed from the slow propulsion described in the first paper. The movements of the horse stomach were investigated (Alexander, 1951a) and it was found that the perfused isolated stomach did not contract strongly enough to expel its contents. Attention then turned to the living animal and a method devised to record gastric contractions by means of a tube passed down the oesophagus. Gastric contractions were unaffected by histamine, carbamylcholine or posterior pituitary extract. By mixing carbon granules of suitable size with food, it was possible to measure the rate of passage of food residues through the alimentary tract of the horse (Alexander, 1946). In view of the length and complexity of this system in the horse it was surprising to find that the time taken by digesta to traverse the tract was approximately the same as in man. A more detailed study became possible with the development of radiographic methods (Alexander and Benzie, 1951). So far as could be ascertained, this was the first publication of radiographs of the equine digestive tract. It was of particular interest to discover that digesta remained in the stomach and small intestine of the suckling foal for a longer time than in the weaned animal. Since abdominal surgery in the horse has been regarded as particularly hazardous, the study of digestion by means of permanent fistulae into the intestine had not been attempted. However, the development of a suitable technique seemed essential and a method was evolved for the fistulation of the caecum (Alexander and Donald,1944). The success of this procedure encouraged the extension of the intestinal surgery to include fistulation and exteriorisation of the small intestine (Alexander, 1951b) and now it has been found possible to fistulate the caecum, ventral and dorsal colons in the same animal (Alexander, 1952a). The ileal fistulae allowed the renstition on the living animal of some of the experiments on the perfused ileum. There appeared to be an association between ileal motility and blood flow (Alexander, 1952b) which supported the observations on the in vitro preparations. The fistulae of the large intestine were used to study movements, products of fermentation and cellulose digestion. Three types of movement were recognised but no evidence of antiperistalsis was obtained. Large amounts of the lower fatty acids were found in the caecum and large colon and the proportion of the various acids differed between the dorsal and ventral colon. It appeared that witholding food depressed cellulose digestion (Alexander, 1952a). The experiments on the small intestine had been confined to a study of the mechanical factors. However, by utilizing the fistulated animals it was possible to study absorption. It was found that feeding glucose produced a hyperglycaemia which was associated with the presence of a high glucose concentration in the ileum. Since no glucose or its j fermentation products appeared in the caecum, it seemed probable that it was completely absorbed in the small intestine. This may explain, in part, the finding that the concentration of glucose in horse blood is about 50% higher than in ruminants (Alexander,1954a). Since the horse is a good example of a. herbivore in which microbial digestion is carried out in the large intestine, studies of digestion in the horse are complementary to those on the ruminant, animals in which microbial digestion takes place in the stomach. The digestive processes in these species have been reviewed (Alexander, 1954b) and it is suggested that the horse is particularly suited for studies of cellulose digestion. During the development of the surgical techniques described, considerable experience was gained in anaesthetising ponies for long periods. A variety of anaesthetics were tried and eventually a satisfactory technique evolved. This has been described in detail and an account given of the anaesthetic deaths which occurred during the course of the operations (Alexander, 1954c). The development of the techniques described has encouraged investigation of the microbial activities of the horse's digestive tract. So far, a specific streptococcus, a lactate fermenting organism (Veillonella gazogenes) (Alexander, Macpherson and Oxford, 1952) and a glucuronide decomposing enzyme have been isolated from the horse colon. This enzyme resembled others which occurred at sites of cellulose in various herbivores (Marsh, Alexander and Levvy,1952). It has been suggested that the enzyme is concerned with the digestion of hemicellulose.

Each part of the hen's oviduct possesses to some extent, the properties of secretion and. moti- lity. Those secretions of the oviduct which contri bute to egg formation have been studied by several authors but the mechanics of egg formation have so far received little attention. The oviduct may be considered to show two types of movement: relatively slow, propulsive movements by means of which the egg is moved as far as the uterus, and relatively quick, expulsive movements which constitute the process of oviposition. The object of this work is to describe some aspects of the physiology of these latter movements, to suggest possible ways in which they are controlled and to compare them with similar movements observed during mammalian parturition.

The Cashmere goat has an annual cycle of hair growth and moulting, which is associated with changes in photoperiod. The first experiment was designed to determine if slow release melatonin implants could be used to delay the spring moult and initiation of hair follicle activity; as has been reported in mink and Blue-foxes and to investigate other endocrine changes associated with the onset of the moulting period. In the second experiment the association between the increase in plasma prolactin concentration and the onset of moulting and hair follicle activity was investigated. The final experiment was designed to determine whether a period of plasma prolactin suppression followed by a rapid increase in plasma prolactin concentration would accelerate the moult and thereby synchronise the onset of moulting within a group of animals. It is concluded that the timing of the spring moult in the cashmere goat can be altered by manipulating plasma prolactin concentrations. Factors other than prolactin may, however, be involved at the follicular level and controlling the response of individual follicles.

No description available.

No description available.

No description available.

No description available.

The experiments in this thesis employed the antibody microprobe technique to study, both in normal rats and in those with a peripheral mononeuropathy, the spinal release of extracellular immunoreactive neuropeptide Y and to determine the origin of such release. In the initial experiments, microprobes bearing immobilised antibodies to neuropeptide Y were inserted into the lumbar spinal cord of urethane anaesthetised normal rats. In the absence of peripheral stimuli microprobes detected a high basal presence of immunoreactive NPY throughout the entire dorsal and ventral horn. Electrical stimulator of large diameter afferents of the ipsilateral sciatic nerve and unmyelinated primary afferents did not significantly alter the spinal release of immunoreactive neuropeptide Y in the spinal cord. Transection of the spinal cord at a low thoracic level resulted in increased levels of immunoreactive neuropeptide Y only in the lower ventral horn. The predominant failure of electrical stimulation and of spinalisation to significantly alter the basal levels of immunoreactive neuropeptide Y suggests that the latter results from spontaneous activity in intrinsic neurones. For studies of rats with a peripheral mononeuropathy, the model of Bennett & Xie was used. Postoperatively the development of mechanical allodynia and hyperalgesia were assessed and animals used at 10-14 days only if they displayed the characteristic behavioural signs associated with this model. In sham animals both sides of the lumbar spinal cord showed a significant spinal release of immunoreactive neuropeptide Y throughout the entire dorsal horn. The site of greatest extracellular levels was the superficial dorsal horn. A similar distribution was also found in the neuropathic animal on the side contralateral to the nerve ligation. On the ipsilateral side of the neuropathic rat however there was a further zone of spontaneous release of immunoreactive neuropeptide Y in the mid and lower dorsal horn (approximately to laminae III, IV and V).