(a) Hypotension was produced by quinuronium in rat, guinea pig, chicken, rabbit and sheep. In the rat this hypotension was antagonised by mepyramine; in rabbits only by atropine; in sheep partially by both atropine and mepyramine. In guinea pig and chicken neither antagonist was effective. (b) Experiments on the blood vessels of the rabbit's ear showed a muscarinic effect of quinuronium, whereas plethysmo- graphic studies on the hind-limb and small intestine of the sheep showed that both histaminic and muscarinic factors were involved in the vascular actions, with the latter predominating. (c) Quinuronium stimulated both the rate and amplitude of contraction of the isolated heart of guinea pig and rabbit. The effect was not muscarinic, but in the absence of a suitable antagonist it was not possible to determine the extent this might have been due to histamine or to histamine-like activity. The stimulant effect of quinuronium on the isolated heart suggested that such a cardiac action could play little part in inducing hypotension and it was concluded that peripheral vaso-dilatation was probably the more important factor. (d) The contractions of the smooth muscle of the intestine and bladder by quinuronium appeared to be muscarinic and the 89. specific potentiating effect of this agent on the action of acetylcholine was evidence of anticholinesterase activity. The findings supported clinical evidence of defaecation end urination produced by quinuronium and antagonised by atropine. (e) Excessive salivation after quinuronium appeared to be attributable to muscarinic effects, whereas the stimulation of gastric secretion by quinuronium was not entirely muscarinic. The potentiating action of quinuronium on acid production induced by acetylcholine was indicative of anticholinesterase activity. It was clear that part of the action of quinuronium on gastric acid secretion in rats was not muscarinic, but in the absence of antagonists of the gastric effects of histamine it was not possible to show whether or not this other action was histaminic. (f) Small doses of quinuronium potentiated the contraction of supra-maximally stimulated skeletal muscle in chicken and rabbit, whereas larger doses produced a neuromuscular block apparently similar to that produced by d-tubocurarine. The effect of quinuronium in depressing respiration in these species was much greater than that of d-tubocurarine at doses which were equi-potent in producing neuromuscular block. This sugnested that respiratory depression of quinuronium was only partially accounted for by neuromuscular blockade. (g) Anticholinesterase activity was shown in whole blood in vitro in a wide variety of species and was confirmed in the live sheep. There was evidence of substrate reversal of the action of quinuronium in vitro, whereas in the living sheep the cholinesteras 90, enzyme did not return to completely normal activity for two weeks, which suggested a partial irreversibility. Sheep were hyper- susceptible to a second dose of quinuronium when this was given within two weeks of the first dose. A number of explanations were proposed. Studies with the cholinesterase "reactivator" pyridine 2-aldoxime methiodide indicated that this agent did not protect or alleviate whole blood cholinesterase inhibition by quinuronium. (h) Quinuronium was shown to liberate histamine from rat skin in vitro and from the skin of rats and mice in vivo. In the rat the evidence for histamina-induced hypotension and gastric acid secretion was substantiated by direct evidence for histamine release; and it seemed that released histamine was at least as important as muscarinic activity in this species. Direct evidence of histamine release from sheep diaphragm in vitro and indirect evidence from increased capillary permeability ("bluedye" test) and from mast cell disruption and degranulation indicate that histamine release is an important part in the overall pharmacodynamic activity of quinuronium in sheep. (a) Experiments with the isolated rabbit ear showed that amicarbalide antagonised the action of acetylcholine on the blood vessels. (b) Further evidence of an atropine like action was obtained from studies on the smooth muscle of the bladder and intestine. c) Amicarbalide stimulated the secretion of gastric acid in the anaesthetised rat and neither atropine nor repyramine antago- nised this. Amicarbalide partially antagonised the action of acetylcholine on gastric acid secretion which was further evidence of an atropine like action. (d) The anticholinesterase activity of amicarbalide was weak by comparison with quinuronium. This result was probably not clinically significant. (e) The release of histamine by amicarbalide was most marked in rat tissue, absent in mice and weak in sheep in vitro and in vivo. The evidence suggests that in the rat, histamine release is a major factor in the toxicity of amicarbalide and in the sheep, histamine release is positive but of less significance.

Some respiratory and circulatory parameters were established for dogs during routine clinical anaesthesia. The possible effects on these parameters of positioning the animals in left lateral, right lateral and dorsal postures were also studied. One hundred clinical dogs and eight experimental dogs were included in this study. The clinical dogs were categorised into two equal groups; group A, for which complete physiological and biochemical data were available and group B, for which the biochemical data were not available. All dogs were anaesthetised by a minimal dose of thiopentone sodium followed by nitrous oxide and halothane throughout the anaesthetic period. PHYSIOLOGICAL PARAMETERS: The respiratory and circulatory parameters which were measured were minute volume, respiratory rate and pulse rate. A review of the literature of the workers noted a decrease in during anaesthesia associated with respiratory rate and tidal volume. showed that a majority minute volume of dogs a decrease in both In man, increases in tidal volume and respiratory rate were frequently observed but the net effect on minute volume was variable, depending on the degree of change in the two components. In this study, a significant positive corelation was found between tidal volume and body weight, and between minute volume and body weight, whilst a significant inverse corelation was established between respiratory rate and body weight. Changes in tidal volume during anaesthesia were not significant. However, respiratory rate and in consequence minute volume showed a significant increase. Minute volume values recorded in dorsal recumbency were found to be significantly higher than the values obtained in lateral postures. In dogs maintained in left lateral and right lateral postures respiratory rate values were comparable, but were significantly lower than the values recorded in dorsal posture. Thus the differences in the minute volume values were determined predominately by the differences observed in the respiratory rates. Pulse rate was found to fall during the interval from ten minutes following induction of anaesthesia until the end of the anaesthetic period. No significant corelation was evident between the pulse rate and body weight or between the pulse rate values obtained in left lateral, right lateral and dorsal postures. BIOCHEMICAL PARAMETERS: The biochemical parameters examined were pH, PaCO2 and Pa02' A review of the literature showed that all authors found an increase in the arterial blood carbon dioxide tension with a moderate to a severe respiratory acidosis in both man and animals. In the present study arterial carbon dioxide tension rose significantly above the preanaesthetic level, and this was associated with a considerable fall in arterial pH. The changes in the standard bicarbonate levels were not significant. The mean PaCO2 value recorded after ix sixty minutes of anaesthesia in dorsal posture was signifi- cantly higher than the mean values obtained in either of the left or right lateral postures. The fall in pH was proportionate to the retention of carbon dioxide. The mean pH values were significantly lower in dogs maintained in dorsal posture than in either of the lateral postures. The standard bicarbonate values recorded in dogs maintained in the three postures were not significantly different. Arterial oxygen tension rose significantly above the control levels. The mean Pa?2 values obtained in the left and right lateral postures were comparable and they were higher than those recorded in dorsal posture. Haemoglobin concentration decreased significantly during anaesthesia, but the extent of this fall did not differ in different postures. As a result of this investigation it is concluded that the exchange of respiratory gases is impaired in spontaneously breathing dogs under anaesthesia and the concomitant progressively developing acidosis is attributed mainly to this cause. The efficiency of ventilation is further reduced in the dorsal posture compared with the lateral. It is recommended that the respiratory blood gases should be intermittently monitored during the anaesthesia of clinical patients, particularly those having hypoxia or acid base abnormalities as part of their clinical syndrome. Adequate oxygenation can be maintained by administering oxygen rich mixtures with the anaesthetic gases but the elimination of carbon dioxide from those patients having high PaCO2 levels will require the animals to be artificially ventilated. It is suggested that the component of respiration most requiring supplementing is the tidal volume, an increase of rate by itself having been shown in the clinical cases which were breathing spontaneously to be inefficient as a compensatory measure.

This work is divided into two sections. The first deals with variations in the blood picture of normal dogs under a variety of conditions and the second with variations in two diseases. In the first section over three hundred dogs have been examined. These dogs came from several different sources and more of varying ages and breeds. The results obtained indicate that the blood picture is influenced to a considerable extent by the age of the clogs and by the environment in which it lives. The red cell counts are mainly affected by age and the total and differential white cell counts by environment. Pregnancy causes variations in both red and white cell counts and these changes are most ierked towards the end of gestation. Oestrus periods cause slight variations in the blood picture but false pregnancy does not. It is possible, in certain circumstances, to diagnose pregnancy by means of a blood picture. Breed does not influence the blood picture in dogs other then greyhounds. The blood picture is not altered appreciably by sex differences, or by exercise, feeding, travelling or work. Twelve different estimations have been investigated and a standard normal blood picture has been drawn up for dogs including all these estimations. The morphological characteristics of the various types of blood cells has been discussed and special staining techniques investigated with regard to eosinophils. The wide ranges of variations, given by other authors, for red and white cell estimations, have been shown to occur and the causes of these variations have been precisely defined. In the second section of this work two clinical conditions, pyometra and mammary tumours, have been investigated. Dogs suffering from pyometra have been shown to have alterations in their blood pictures and these changes have been correlated with the clinical signs and the condition of the uterus. No significant changes in the blood picture was observed in animals with mammary tumours unless necrosis was present.

hen a group of sheep were fed 1 gramme of copper sulphate daily there was no demonstrable effect on their blood copper levels. Three out of six may have shown a premonitary sign of poisoning in a form of photosensitisation. It was sixteen weeks before one died with the typical signs and. 'nost-mortem findings of copper poisoning, but this was followed by another in two weeks. Blood analyses indicated that there was a considerable rise of loosely- bound copper in the plasma in the terminal crisis. When two of the survivors were given 54 mg. molybdenum daily by mouth, their blood copper level rose while that of controls remained t7-! same. This increase was accounted for mainly in the plasma fraction but, in contrast to the findings in the haemolytic crisis of copper poisoning, the proportions of globulin-bound and loosely-bound copper remained approximately the same. The animals were not clinically affected and at the end of the period there was some evidence that their liver copper had been reduced. The distribution of copper within the liver was found to be different, in animals which had not died from copper poisoning, from that in animals which had. In a further experiment, five sheep were kept on a constant diet and their intake and output of copper was measured. 54 mg. molybdenum per day, given by mouth, was found to raise serum copper levels, depress urine copper and raise faecal copper output. The effect of 2.0 g. sulphate per day was to enhance these effects, but sulphate alone did not produce the same results. Post-mortem examination of the kidneys of two of these animals revealed tubular reabsorption of copper and damage to tubular epitheluim.

Aspects of the biology of the swimming crab, Portunus pe/agicus (Linnaeus, 1758). were investigated from trawl catches from offshore fishing grounds in Bahraini waters (designated areas A [northern], B [north-eastern] and C [southern], a total area of 1636 km2 ) and inshore grounds (traps) around Bahrain over 14 months. P. pe/agicus were found over a considerable range of temperatures (16-35 °C) and salinities (39-57%0). The abdomen of female crabs shows a distinct change in shape at about 7 cms carapace width (CW), when the pubertal moult takes place. In male crabs the shape of the abdomen remains unchanged throughout life. Breeding season lasts from March to November, with peck numbers of ovigerous females between June and September. Sex ratio analysis has shown that mature female crabs migrate from the shallow waters of areas A and C to the deeper water of area B. Since 73% of all ovigerous females caught were in area B, it was designated the major spawning ground. Females spawn at least twice throughout life and fecundity reaches as high as 1.54 million eggs brood-I. Larvae were found over a more restricted temperature (31-35 °C) and salinity range (40-48%0) than the adults. Certain regions of areas A, C and the whole of area D (west) have been identified as the major nursery grounds. Two recruitment periods were identified - a short period (June-July) and a much longer period (December-April). Relative abundance (crabs km-I trawled) varied spatially and seasonally being high during the summer months and low during winter through to spring. CW of crabs in areas A and B exhibits isometric growth with carapace length (CL). In area C, however, both dimensions indicated allometric growth with relatively shorter CL in the larger crabs. Male crabs were found to be relatively heavier than females at 2 cms CW, becoming more so above 6 cms CWo The growth rate for both genders ranged from 0.5 to 2.5 cms CW month-I. Base-line recommendations for the crab fishery management in Bahrain from this study include - minimum size limits, banning the capture of ovigerous crabs, banning fishing in the nursery areas as well as modifications to fishing gear.

Commercial fishing for Pecten maximus and Aequipecten opercularis has taken place in Shetland since the late 1960’s and early 1970’s, respectively, with fluctuations in landings of both species during this time. Recognition of the importance that shellfish fishing contributes towards maintaining a diverse economy in a rural area, coupled with concerns in the 1990’s about the potential for overfishing, prompted by reductions in the abundance of some shellfish species, the Shetland Shellfish Management Organisation Ltd. was formed, with a remit to implement local management of shellfish stocks, where necessary. The collection of biological data was started and the completion of log books begun in 1999 and 2000, respectively, to provide data to assess the species, with a view to their sustainable management. Von Bertalanffy growth parameters were determined for contemporary samples on both species and on historical samples of P. maximus. The asymptotic shell length, as a measure of growth, was examined in relation to the environmental variables of sediment composition and depth. Growth studies were carried out on juveniles to measure sub-annual growth. The gonadal condition through time in the adult stocks was assessed, changes in gonad condition were related to spawning activity by collection of spat on artificial collectors. Seasonal and spatial differences in yield of adductor muscle and gonad from experimentally derived, and commercial yield data, was analysed. The assessment of the fishery utilised fisher knowledge on the distribution of stocks. Catch Per Unit Effort and mortality rates data were calculated. The overall Spawning Stock Biomass was estimated for P. maximus using the swept area method. Long-term data from processing factories were incorporated into the fisheries assessment. The assessment indicates poor catches of A. opercularis for many years, and a recovery in abundance of P. maximus on some fishing grounds since the low catches experienced in 2000.

The experiments described in this thesis were performed to study and evaluate a number of relevant issues associated with the YY male technology. YY males are expected to produce all-male progeny. However, a small proportion of females have usually been observed in the progeny of XX x YY crosses. A series of experiments evaluating the effect of temperature and salinity on sex ratio in sexually undifferentiated putative all-female, all-male and YY males were conducted. High temperature (36°C) was observed to affect the sex ratio towards male and towards female in different circumstances. Purebred YY males (Egypt-Swansea strain) were found to be sensitive to high temperature. No effect of salinity on sex ratio was observed. Improving the growth of genetically male tilapia (GMT) through crossbreeding has been initiated. An initial study showed the hybrids had better growth than purebred progeny (Abucay, 1996). A follow up study evaluating the growth and sex ratio of progeny in a 2 x 2 diallele cross of Egypt-Swansea and Egypt-ICLARM strains using YY males as broodstock was performed. A parallel study was also conducted to determine the capacity of YY males in the Egypt-Swansea strain to sire all male progeny in crosses with females from a number of strains in O. niloticus. In the diallele cross, the reciprocal hybrids had a higher mean growth that the smaller parent and parental mean but not higher than the larger parent. In the parallel study, YY males were observed to be capable of siring high proportion of male progeny (93.12 to 100%) in the inter strain crosses. The growth of GMT, genetically female tilapia (GFT) and mixed-sex tilapia (MST) was evaluated; (i) during a period of androgen hormone treatment designed to alter the phenotypic sex, (ii) during the post-treatment period, and (iii) during the late life stages in monosex and mixed-sex culture environments. GMT was observed to exhibit faster growth at the early ages. No anabolic effect of the hormone was observed during the period of hormone treatment and posttreatment. The sex-reversed genetic females appeared to grow better than the genetic males during the late life stages. The culture of all females appears to have great potential. A series of experiments were performed to evaluate factors affecting sex reversal. The effect of not changing the water and increasing the temperature during hormone treatment was evaluated. The possible leaching out of hormone from hormone-treated feed was also investigated. Some of the sexually undifferentiated fry reared in water previously used for hormone treatment were sex-reversed indicating that hormone residues had accumulated during previous hormone treatment. Increasing the temperature during hormone treatment was observed to improve the efficiency of sex reversal, particularly feminisation. Results show that hormone leaches from hormone-treated feed suggesting that the observed accumulation of hormone residues could be partly due to leacheates.

The tilapiine cichids of the genus Oreochromis are an increasingly important component of aquaculture in many countries. Aquaculture in Malawi is expanding rapidly and its importance may increase if local cichlid fisheries continue to decline. There is concern that sympatric species (O. shiranus and O. karongae) are hybridizing in farm ponds. The ease with which Oreochromis species hybridize is of much concern to the maintenance of their biological diversity. Mate choice and courtship behaviour were investigated in the allopatric species, O. mossambicus and O. spilurus, and their hybrid. Pure-bred females largely mated assortatively and behaved differently to conspecific and heterospecific males. Females mated with heterospecifics if conspecific males were not available. Hybrid females showed a preference for O. mossambicus. Differences in behaviour largely predicted mate choice in pure-bred fish. O. karongae is one of three species belonging to the unique Oreochromis (Nyasalapia) species flock of Lake Malawi ('chambo'). The incidence of hybridization in farm ponds was examined using allozyme, RAPD and morphological analysis. Markers that distinguished between O. shiranus and chambo were found with both molecular genetic techniques. Markers for each chambo species were not detected. O. shiranus and chambo were discriminated using eight morphometric variables. Chambo species were discriminated using morphometries, meristics and colouration. Hybrids of O. shiranus and chambo were detected in all ponds sampled from three sites in Malawi. No F, hybrids were detected and introgression was common. Discrepancies in fish identification illustrates the merits of using several techniques when identifying post-F, hybrids. Morphological analysis was least effective in identifying hybrids. The implications of hybridization and possible escapes into the wild are discussed in relation to the impacts on aquaculture and on the unique cichlid species endemic to Lake Malawi. Recommendations for the management of Oreochromis in aquaculture are considered in relation to ecological and social issues. Processes that maintain reproductive isolation between Oreochromis species are discussed.

The purpose of this study was to determine the daily energy requirements of ponies native to the U.K., living on upland areas. This information can be used to improve the management of ponies kept under these conditions. The objectives of this thesis were to i) determine the effects of speed and terrain on the energy costs of ponies when walking, ii) measure seasonal differences in the hair coat, iii) estimate the effect of a wet winter coat on metabolic rate, iv) determine the proportion of a day spent by free-living ponies in feeding, walking, standing and lying, v) estimate the total distance moved daily by these ponies, and vi) describe the relationships between weather conditions and the behaviour and location of ponies. In the first study, the energy costs of walking were measured in four Shetland and two Exmoor ponies by using open-circuit, indirect calorimetry. The energy cost of activity, above that for standing, was independent of speed and averaged 1.02 J/kg liveweight/m travelled. An Oxylog, a portable breath-by-breath oxygen analyser, was used to determine effects of terrain on the energy cost of walking using five Shetland ponies. In the second study, physical parameters of the winter and summer hair coats of six Shetland ponies were compared. In the third study, six Exmoor pony mares, kept in an enclosed area of fell in Cumbria, were observed in later winter (W) when they were pregnant, and in summer (S) when they were lactating. The results showed that the energy costs of activity (walking and grazing) were greater in winter than in summer. Therefore, seasonal adjustments in energy requirements are needed to allow for changes in activity as well as changes in heat loss. Recommendations are made regarding the management strategies for ponies kept outdoors.

No description available.