OAR@UM Collection:

Interferon-ɑ and sickness behaviour : a study of the dose and time dependency of interferon-ɑ-induced anhedonia and fever

2023-07-05T07:23:29Z

Title: Interferon-ɑ and sickness behaviour : a study of the dose and time dependency of interferon-ɑ-induced anhedonia and fever Abstract: The use of recombinant human Interferon-ɑ2A for the treatment of more than 14 malignancies and virologic diseases is acknowledged world-wide, in over 40 countries. However, its use has been hampered by the many side effects accompanying its therapy, of which depression and suicidal ideations are the extreme cases. Significant research effort has gone into understanding the neural and molecular mechanisms of action of this cytokine, but to date there exist gaps in our understanding of the underlying fine mechanistic details. The side effects of Interferon-a can be described as typical Sickness Behaviour (a coordinated set of behavioural changes that develop in sick individuals during the course of an infection). A Model of Anhedonia was used as the paradigm within which to test and investigate the dose and time dependency of the effects of recombinant human Interferon-a2A (rHIFN-ɑ2A)· The species-specificity of rHIFN-ɑ2A in rats was also studied within this paradigm. The effects of IFN on temperature were used to monitor the activity of the drug in the rats, while anhedonia (measured as a change in the consumption and preference for 1%, 8% and 32% sucrose solutions) was used to assess the impact of IFN on positive reinforcement. From the results obtained rHIFN-ɑ2A was confirmed to be 100 to 1000 times less potent than rat interferon-ɑA (RIFN-ɑA) in rats. More importantly, new insights into the mechanisms of action of rHIFN-ɑ2A on anhedonia and fever were suggested. However, the whole picture is far from complete and this project just represents a first attempt to improve our knowledge of Interferon neurochemistry. This and future studies could eventually lead to the development of appropriate drugs that dampen the undesirable side effects of Interferon-ɑ therapy, allowing patients to make full use of an otherwise effective therapy. Description: B.SC.(HONS)CHEMISTRY&BIOLOGY

The use of remote sensing and GIS-models in assessing the impact of levels of suspended solids in coastal waters on environmental quality and marine life

2022-09-26T11:11:09Z

Title: The use of remote sensing and GIS-models in assessing the impact of levels of suspended solids in coastal waters on environmental quality and marine life Abstract: The aim of the present work was to apply remote sensing and GIS-models in the assessment of suspended solids in coastal surface waters, as arising from non-point land-based sources. Furthermore, the effect of turbidity arising from suspended solids on the marine benthos in particular, Posidonia oceanica (L.) Delile meadows was investigated. The methodology was based upon modelling the route by which suspended solids can reach coastal surface waters from land. This involved creating a digital elevation map using triangulated irregular networks and deriving a baseline runoff model from it. The baseline runoff model and regression analysis for specific land covers were used in order to determine the sediment loading in the coastal areas. The water quality of coastal surface waters was mapped using archived Landsat TM data. Two different approaches were adopted: empirical analysis and the use of artificial neural networks. Benthic habitats in shallow coastal waters were mapped using archived Landsat TM data. This involved the use of principal components analysis and the use of artificial neural networks. Multi-criteria evaluation was used in order to identify coastal areas vulnerable to accumulation of solids and transferring them to the marine environment. This study showed that when annual total suspended solids loadings were taken into consideration, the highest loading was always recorded at Salina Bay whilst for storm events with precipitation levels lower than 17 mm, the highest suspended solids loading was recorded in Birzebbugia. More than 2 million kg of suspended solids can be discharged into the marine environment during a 15-year return period flash flood of 200 mm. These results were coherent with the results of multi-criteria evaluation which determined that the areas mostly vulnerable to accumulation of suspended solids and conveying them to the marine environment were localised to mouths of valleys. These areas corresponded to marine areas which showed significant levels of turbidity as established from Landsat TM imagery. Overlaying maps showing areas vulnerable to pollution due to turbidity on the benthic habitats maps showed that seagrasses are the benthic community found in shallow coastal waters mostly exposed to significantly high levels of suspended solids. This study indicated that reduced water transparency can affect Posidonfo oceanica meadows. The ecological significance of this was discussed. Description: PH.D.BIOLOGY

Investigations on feeding rates, feeding frequency and compensatory growth of gilthead sea bream, Sparus aurata (L.)

2022-09-27T06:56:07Z

Title: Investigations on feeding rates, feeding frequency and compensatory growth of gilthead sea bream, Sparus aurata (L.) Abstract: Three growth trials were performed on S. aurata, which is of importance to the aquaculture industry in the Mediterranean region. In the first investigation, a feeding trial was conducted to investigate the influence of feeding rates on the growth performance. Five feeding rates were employed, 0.5, 1.0, 1.35, 1.7 and 2.0% body weight (BW) /day. The fish increased in body weight, with time for all feeding regimes. At the end of the trial, the feeding rate of 1.7%BW/day gave the best growth performance in terms of SGR, but this growth was not significantly higher (p < 0.05) than that observed with 1.0%BW/day. The feeding regime of 1.0%BW/day gave the best performance and improved feed utilisation overall with regard to food conversion ratio (FCR), feeding efficiency (FE), protein efficiency ratio (PER), apparent net protein utilisation (ANPU) and apparent net lipid utilisation (ANLU). This should be seen both in the light of economical as well as environmental implications. No important differences were observed in the carcass and fillet composition or condition factor (K). Histological studies showed an increased lipid deposition in the liver with increased feeding rates. In the second experiment, a feeding trial was carried out to investigate the influence of feeding frequency on growth performance and food utilisation. Five feeding regimes were employed, once/day (morning), once/day (afternoon), twice/day, 3 times/day and 4 times/day. The best growth performance with improved food utilisation was obtained in feeding frequencies once a day (in the morning) and 4 times a day. SGR, FCR, FE, PER and ANPU were significantly similar (p < 0.05) for both these feeding regimes. From the point of view of food utilisation, feeding once a day in the morning may be considered the optimum feeding frequency. No important differences were noted in the carcass and fillet composition or the condition factor and hepatosomatic index. Histological studies showed an increased of lipid deposition in the liver with increased growth performance. In the third study compensatory growth was investigated. A feeding trial was carried out to investigate the possibility of using the phenomenon of compensatory growth to improve growth and food utilisation. Five feeding cycles were employed: daily feeding, one week of starvation followed by one week feeding (1:1), two weeks of starvation followed by two weeks of feeding (2:2), three weeks of starvation followed by three weeks of feeding (3:3) and six weeks of starvation followed by six weeks of feeding (6:6). By the end of the trial, fish subjected to a feeding cycle of 3 weeks starvation followed by 3 weeks satiation feeding produced comparable results in terms of growth performance to fish that were fed daily. These showed improved food utilisation in terms of FCR, FE, PER, ANPU and ANLU compared to those on the other treatments. Carcass and fillet analysis of protein, lipid, moisture and ash showed some differences with the most notable being the relatively higher moisture levels in both carcass and fillet, as well as the relatively lower crude lipid levels in both carcass and fillet. Histological studies showed that lipid deposition in the liver of fish fed on 3:3 and on the basis of daily satiation was higher than in the rest of the fish. The studies provide evidence of the adaptation of the fish to starvation followed by what may be termed compensatory growth, once feeding was resumed. Description: PH.D.BIOLOGY

The structure of the molluscan assemblages of sea-grass beds in the Maltese Islands

2022-09-12T10:15:14Z

Title: The structure of the molluscan assemblages of sea-grass beds in the Maltese Islands Abstract: Macrobenthic molluscs associated with meadows of the sea-grasses Posidonia oceanica and Cymodocea nodosa were sampled between November 1993 and November 1995 at about bimonthly intervals. Samples were collected from the Posidonia meadow at four depths (6m, 11m, 16m and 21m) using a suction sampler and a hand-towed net. Samples were collected from the Cymodoce.&meadow at two depths (4m and 8m) using a suction sampler. Phenology of both sea-grasses was studied, and sediment granulometry and other sediment parameters were measured. Species composition, abundance, and biomass of Mollusca were determined for each sample, and community parameters (species richness, diversity, evenness, and dominance) were estimated. The molluscan assemblages were analysed using classification and ordination, analysis of similarities (ANOSIM), and similarity percentages (SIMPER). The structure of the P. oceanica and C. nodosa meadows appeared to be influenced by water depth, resulting in distinct types of meadows at different depths. Shoot density of Posidonia decreased steadily with depth. The number of leaves per shoot varied more with season than with depth. Leaf length and width changed significantly with season but not with depth. The leaf area index (LAI) and leaf standing crop (LSC) showed significant seasonal changes; higher values were recorded in the warmer than in the cooler months. Only LAI showed significant variation with depth. For Cymodocea, shoot density varied significantly with depth, but not with season; the LAI and LSC were higher at the shallow (4m) station than at the deeper (8m) one. Seasonal changes in LSC were significant between but not within stations. Sediment granulometry of the substratum of both Posidonia and Cymodocea meadows was very similar at all depths, and the near absence of mud and of very fine sand indicates that the areas appear to be under the influence of considerable water movement, and little influenced by the presence of the sea-grasses. The organic carbon content of the sediment was not significantly different between stations for either meadow. The Mollusca of the Posidonia meadow were differentiated into foliar, and rhizome layer/matte assemblages. Altogether, five polyplacophorans, 99 gastropods, and 28 bivalve species, represented by 7559 individuals, were collected. Of this, about 65% of the total individuals were inhabitants of the rhizome layer/matte. Only 16 species of molluscs were widespread and abundant, most of them gastropods of the leaf stratum. Molluscan species richness, abundance, and distribution along the depth gradient were influenced mainly by the structure of Posidonia meadows and by water movement. The biomass of Mollusca (totalling 22878.3mg AFDW) was essentially contributed by gastropods (72-99.8%). Significant changes in biomass generally occurred with season and with depth. The use of multivariate analyses delimited the molluscan taxocene into: (1) a shallow water (6m and 1 lm) assemblage; and (2) a deep water (16m and 21m) one. A comparison between the two sampling methods used showed that the suction sampler collected twice the number of species and half the number of individuals of the handtowed net. The suction sampler is probably a better method for qualitative and quantitative sampling of the molluscan assemblages associated with Posidoma meadows. [...] Description: PH.D