Efeito do cloro no desenvolvimento e na tiróide da Til��pia Moçambicana (Oreochromis mossambicus)

Dissertação mest., Biotecnologia, Universidade do Algarve, 2009

Chemical communication in the Mozambique tilapia: a role for amino acids

The Mozambique tilapia (Oreochromis mossambicus) is a maternal mouthbrooding cichlid from the southern Africa. The olfactory sensitivity of the species to 20 amino acids was assessed using the electro-olfactogram (EOG). We estimated whether the olfactory potency of the polar fraction of male urine can be explained by the presence of identified amino acids. In addition, filtrate and amino acid mixture of the urine of Nile tilapia were used to estimate their olfactory potency for O.mossambicus. Finally, concentrations of the main amino acids were measured in the urine of males of different social status and the correlations between amino acid concentration and hierarchical status were explored. L-cysteine, L-glutamine and L-threonine were the most potent stimuli at M while L-proline and L-aspartate were the least potent. Four groups of amino acids were identified according to their thresholds of detection and three groups – according to the similarity of their ɣ-factors. The estimated threshold of detection for O.mossambicus mixture was higher than that for the filtrate. On the contrary, the threshold of detection for the mixture of Nile tilapia was lower than that for the filtrate The concentration of L-arginine in the urine was positively correlated with fish dominance index. Both L-arginine and L-glutamic acid concentrations had much greater variability in dominant males (DI˃0.5) than in subordinate males (DI˂0.5). The urinary concentrations of L-phenylalanine had similar variability in dominant and subordinate groups. The Mozambique tilapia has olfactory sensitivity to all twenty amino acids tested. The fish showed more acute sensitivity to conspecific urine filtrate than to the heterospecific. Olfactory potency of O.mossambicus filtrate can be largely but not fully explained by the presence of L-arginine, L-glutamic acid and L-phenylalanine. Larginine and L-glutamic acid may indicate the dominance status of the fish and, possibly, individual identity.

‘Biochemical Responses to Heavy Metals in Oreochromis mossambicus with special reference to Metal Detoxifying Mechanism

The present work is focused on the organelle and biochemical responses to heavy metal exposure in the fish Oreochromis mossambicus giving particular importance to the metal detoxifying machinery of the organism. The thesis is an outcome of the effort aimed at developing practicable monitoring techniques to deliver guidelines for biological effect monitoring and the need for specific biochemical methods to detect biological effects of heavy metals that can be interpreted in terms of the health status of the individual organism and eventually alterations in vital processes as growth and reproduction. The efficiency of the metal detoxifying metallothioneins which is an attractive tool for biological monitoring, their role as scavengers of trace metal ions and thus in relieving the biological machinery from their toxicity effects are important themes of this study. Efforts have also been made to test the reliability of the spill over hypothesis of the action of metallothioneins (Winge et a1.,1973) and their use as a biological barometer of heavy metal stress.

Caracterização da reprodução e ensaios de crescimento da Til��pia Moçambicana (Oreochromis mossambicus, Peters 1852)

Três grupos constituídos por indivíduos de til��pia da espécie Oreochromis mossambicus foram observados por um período de 6 meses e registado os seus comportamentos reprodutivos, número de fêmeas em incubação e o número de fry que nasceram durante este tempo. Cada grupo apresentava proporções sexuais distintas (macho:fêmea), nomeadamente, 1:3, 1:4 e 2:2. Após a evolução do estágio das fry a alevins, foram testados nestes indivíduos 3 dietas experimentais: a dieta RT (ração para til��pia), a dieta RD (dieta para douradas) e a Mix (uma mistura de 50% de cada uma das rações anteriormente referidas). Os alevins foram distribuídos em 9 tanques, 20 indivíduos/tanque, existindo três réplicas por dieta e todos se encontravam a uma temperatura de 28 ± 1ºC. Foram alimentados 3 vezes por dia durante 11 semanas, fazendo jejum 1 dia por semana. A cada 2 semanas, os indivíduos eram pesados e medidos e a quantidade de ração era ajustada de acordo com o seu crescimento. Como forma de se reduzir o stress neste procedimento de medição e pesagem, utilizaram-se três anestésicos a diferentes concentrações: MS-222 (0,15, 0,25 e 0,35ml L-1), óleo de cravo (0,10, 0,15 e 1,2ml L-1) e 2-fenoxietanol (0,40, 0,60, 0,80 e 1,00ml L-1). Registaram-se os tempos de indução e recuperação e avaliou-se qual o anestésico mais eficaz. No final do ensaio, os indivíduos foram mortos por choque térmico, filetados e sujeitados a estudos para avaliação do teor de proteína, l��pidos, humidade e cinzas. No final de todo este trabalho experimental verificou-se que existiu reprodução nos Grupos 1 e 2 durante os 6 meses e que a melhor proporção sexual é 1:3 (macho:fêmea). Observou-se que as fêmeas que produzem mais posturas seguidas têm um menor número de fry por postura e as que fazem um maior intervalo de tempo entre cada postura, produzem posturas com um maior número de fry. Para qualquer uma destas opções das fêmeas, a taxa de mortalidade das fry é muito reduzida. No ensaio das dietas, os alevins aceitaram com boa aceitabilidade as três dietas mas com o decorrer do tempo, os indivíduos da dieta RD começaram a ganhar hemorragias em algumas partes do corpo. Não existiram diferenças significativas entre as dietas. A dieta Mix foi a que mostrou melhores resultados finais com um peso e comprimento máximos de 4,51 ± 3,39g e 3,36 ± 1,81cm, respetivamente. Para os valores de WG, SGR e FCR também não existiram diferenças significativas para as três iv dietas, sendo a dieta Mix a obter os valores máximos para WG (4,71g) e SGR (2,97% dia-1) mas com o FCR baixo (12,45 g/g). Para os resultados da composição química obtiveram-se diferenças estatisticamente significativas (P < 0,05) nos dados da proteína e humidade. A dieta RT foi a que apresentou um maior teor de proteína (18,53%) e os valores máximos para a humidade foram nas dietas RT (80.54%) e Mix (80,57%). Os l��pidos e as cinzas não tiveram diferenças significativas e os valores máximos para estes dois parâmetros foram 1,38% e 1,50% na RT, respetivamente. Para os anestésicos estudados existiram diferenças significativas (P < 0,05) para os tempos de anestesia e recuperação pertencentes ao MS-222 e 2-fenoxietanol; o óleo de cravo apenas apresentou diferenças significativas no tempo de indução. As concentrações que mais eficazes se mostraram para anestesiar Til��pias Moçambicanas foram: 0,25ml L-1 para o MS-222, 0,10ml L-1 para o óleo de cravo e 0,80ml L-1 e 1,00ml L-1 para o 2-fenoxietanol. Os resultados deste trabalho sugerem que a reprodução de Til��pia Moçambicana se consegue com bastante sucesso quando se proporcionam condições ótimas, principalmente, a temperatura que é um dos fatores mais importantes; é uma espécie que aceita com facilidade variados tipos de rações; e os anestésicos utilizados mostraram-se eficazes a anestesiar os juvenis desta espécie apesar de ser necessário continuar o estudo com mais concentrações.

Reduction of the “ngege”, Oreochromis esculentus (Teleostei: Cichlidae) populations, and resultant population genetic status in the Lake Victoria region

Ngege, Oreochromis esculentus, originally formed the mainstay of the Lake Victoria Region (LVR) fisheries. Together with its indigenous congener O. variabilis, it was displaced from Lakes Victoria and Kyoga of LVR and was found to survive as isolated small populations within the peripheral minor lakes and reservoirs around the two lakes. Displacement of the two LVR indigenous tilapiines was thought to be principally driven by changed lake environment and predation by the introduced Nile perch, but also competition and genetic swamping by the closely related introduced and comparatively more ecologically versatile tilapine species. In a study carried out in the LVR between 1993 and 2003, micro satellites and RAPD markers were used to analyse the remnant populations so as to establish the population structure and extant genetic diversity of O. esculentus. Analyses indicated that the surviving O. esculentus retained a high proportion of genetic diversity with high differentiation between units an indication of genetic exchange between indigenous and introduced Nile tilapia where the two forms co-existed. While this heightened concern for genetic swamping of the remnant population units by the introduced tilapiines it was noteworthy that in a few of the satellite lakes where the O. esculentus was dominant evidence for introgression was weak.

Investigations of the present factors affecting the population characteristics and relative abundance of nile perch (Lates niloticus) at selected trawling sites of western part of Lake Victoria, Uganda, Kagegi Gulf

This report is based on the investigation of the factors affecting population characteristics and relative abundance of Nile perch in selected sites of Kagegi Gulf Lake Victoria Uganda in the month of November 2006. Nine (9) stations were sampled at depth strata of 0-10, 10-20, 20-30 and 30-40 m the mean catch rates were as follows; 8.75±5.5, 4.77±2.3, 6.33±0.3 and 1.34±1.1 tonnes per square kilometer respectively. The catch rates differed at various depth levels with p-value of 0.2940 at 5% level of significance. Limnological parameters were temperature 25.15±0.28, 23.68±0.20, 24.74±0.13 and 25.3±0.20°C; pH of 8.0±0.00, 7.7±0.11; 7.66±0.33 and 6.32±0.14, dissolved oxygen 7.37±0.24, 6.44±0.30, 6.32±0.14 and 6.22±0.14 mg/l; Total nitrogen 589.82±97.2, 514.34±68.8, 690.44±257.8 and 809.03±45.02 µgL-respectively with a p-value of 0.4392 at 5% level of significance. Prey type of Nile perch indicated 65.2% of haplochromine in 0-10 m depth and other strata >10 metre were dominated by Caridina nilotica. Generally investigations indicated that the catch rates of Nile perch at Kagegi gulf in various depth strata probably depended on both the physical and chemical parameters mentioned above.

A multi-component pheromone in the urine of dominant male tilapia (Oreochromis mossambicus) reduces aggression in rivals

Males often use scent to communicate their domi- nance, and to mediate aggressive and breeding behaviors. In teleost fish, however, the chemical composition of male pher- omones is poorly understood. Male Mozambique tilapia, Oreochromis mossambicus, use urine that signals social status and primes females to spawn. The urinary sex pheromone di- rected at females consists of 5β-pregnane-3α,17α,20β-triol 3- glucuronate and its 20α-epimer. The concentration of these is positively correlated with male social rank. This study tested whether dominant male urine reduces aggression in receiver males, and whether the pregnanetriol 3-glucuronates also re- duce male-male aggression. Males were allowed to fight their mirror image when exposed to either: i) water control or a chemical stimulus; ii) dominant male urine (DMU); iii) C18- solid phase (C18-SPE) DMU eluate; iv) C18-SPE DMU eluate plus filtrate; v) the two pregnanetriol 3-glucuronates (P3Gs); or vi) P3Gs plus DMU filtrate. Control males mounted an increas- ingly aggressive fight against their image over time. However, DMU significantly reduced this aggressive response. The two urinary P3Gs did not replicate the effect of whole DMU. Neither did the C18-SPE DMU eluate, containing the P3Gs, alone, nor the C18-SPE DMU filtrate to which the two P3Gs were added. Only exposure to reconstituted DMU (C18-SPE eluate plus filtrate) restored the aggression-reducing effect of whole DMU. Olfactory activity was present in the eluate and the polar filtrate in electro-olfactogram studies. We conclude that P3Gs alone have no reducing effect on aggression and that the urinary signal driving off male competition is likely to be a multi-component pheromone, with components present in both the polar and non-polar urine fractions.

Towards executable specification : combining i* and AgentSpeak(L).

Agent-oriented conceptual modelling (AoCM) approaches in Requirements Engineering (RE) have received considerable attention recently. Semi-formal modeling frameworks such as i* assist analysts in requirements elicitation and reasoning of early-phase RE. AgentSpeak(L) is a widely accepted agent programming language. The Strategic Rationale (SR) model of the i* framework naturally lends itself to AgentSpeak(L) programs. Furthermore, the Strategic Dependency (SD) component of the i* framework prescribes the interaction between the agents in a multi-agent environment. This paper proposes a formal methodology for transforming a SR model to an AgentS- peak(L) agent. The constructed AgentSpeak(L) agents will then form the essential components of a multi-agent system, MAS.

Enhanced human bone marrow stromal cell affinity for modified poly(L-lactide) surfaces by the upregulation of adhesion molecular genes

To enhance and regulate cell affinity for poly (l-lactic acid) (PLLA) based materials, two hydrophilic ligands, poly (ethylene glycol) (PEG) and poly (l-lysine) (PLL), were used to develop triblock copolymers: methoxy-terminated poly (ethylene glycol)-block-poly (l-lactide)-block-poly (l-lysine) (MPEG-b-PLLA-b-PLL) in order to regulate protein absorption and cell adhesion. Bone marrow stromal cells (BMSCs) were cultured on different composition of MPEG-b-PLLA-b-PLL copolymer films to determine the effect of modified polymer surfaces on BMSC attachment. To understand the molecular mechanism governing the initial cell adhesion on difference polymer surfaces, the mRNA expression of 84 human extracellular matrix (ECM) and adhesion molecules was analysed using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). It was found that down regulation of adhesion molecules was responsible for the impaired BMSC attachment on PLLA surface. MPEG-b-PLLA-b-PLL copolymer films improved significantly the cell adhesion and cytoskeleton expression by upregulation of relevant molecule genes significantly. Six adhesion genes (CDH1, ITGL, NCAM1, SGCE, COL16A1, and LAMA3) were most significantly influenced by the modified PLLA surfaces. In summary, polymer surfaces altered adhesion molecule gene expression of BMSCs, which consequently regulated cell initial attachment on modified PLLA surfaces.

Synthesis of 4-arm star poly(L-Lactide) oligomers using an in situ-generated calcium-based initiator

Using an in situ-generated calcium-based initiating species derived from pentaerythritol, the bulk synthesis of well-defined 4-arm star poly(L-lactide) oligomers has been studied in detail. The substitution of the traditional initiator, stannous octoate with calcium hydride allowed the synthesis of oligomers that had both low PDIs and a comparable number of polymeric arms (3.7 – 3.9) to oligomers of similar molecular weight. Investigations into the degree of control observed during the course of the polymerization found that the insolubility of pentaerythritol in molten L-lactide resulted in an uncontrolled polymerization only when the feed mole ratio of L-lactide to pentaerythritol was 13. At feed ratios of 40 and greater, a pseudo-living polymerization was observed. As part of this study, in situ FT-Raman spectroscopy was demonstrated to be a suitable method to monitor the kinetics of the ring-opening polymerization (ROP) of lactide. The advantages of using this technique rather than FT-IR-ATR and 1H NMR for monitoring L-lactide consumption during polymerization are discussed.

L'étendue internationale des nouvelles firmes de hautes technologies: le rôle du capital humain et de l'intention stratégique des fondateurs

De récentes recherches ont mis l���accent sur l���importance pour les nouvelles entreprises internationales de l���existence de ressources et de compétences spécifiques. La présente recherche, qui s’inscrit dans ce courant, montre en particulier l���importance du capital humain acquis par les entrepreneurs sur base de leur expérience internationale passée. Mais nous montrons en même temps que ces organisations sont soutenues par une intention délibérée d’internationalisation dès l���origine. Notre recherche empirique est basée sur l���analyse d’un échantillon de 466 nouvelles entreprises de hautes technologies anglaises et allemandes. Nous montrons que ce capital humain est un actif qui facilite la pénétration rapide des marchés étrangers, et plus encore quand l���entreprise nouvelle est accompagnée d’une intention stratégique délibérée d’internationalisation. Des conclusions similaires peuvent être étendues au niveau des ressources que l���entrepreneur consacre à la start-up : plus ces ressources sont importantes, plus le processus d’internationalisation tend à se faire à grande échelle ; et l�� aussi, l���influence de ces ressources est augmenté par l���intention stratégique d’internationalisation. Dans le cadre des études empiriques sur les born-globals (entreprises qui démarrent sur un marché globalisé), cette recherche fournit une des premières études empiriques reliant l���influence des conditions initiales de création aux probabilités de croissance internationale rapide.