Selenium (Se) is an essential trace element to most living organisms, however when compared to other ingested essential trace elements Se has the lowest margin of safety between essential and toxic concentrations. Oviparous vertebrates, especially fishes, are highly susceptible to dietary Se toxicity. Greater incidences of deformities and/or mortalities have been observed in F1 generation larval fishes whose parents were exposed to excess dietary Se in the form of selenomethionine (SeMet), however little information is available on effects of chronic dietary SeMet exposure to adult fish and persistent effects of in ovo SeMet exposure to F1 generation fish. This thesis investigated effects of chronic dietary exposure of excess Se in the form of SeMet on swimming performance (Ucrit), oxygen consumption (MO2), stored energy (triglycerides and glycogen), and the physiological stress response (cortisol production) in adult zebrafish (Danio rerio), as well as immediate (incidence of deformities and mortality) and persistent (e.g. changes in Ucrit, MO2, bioenergetics, the physiological stress response and reproduction) effects of in ovo exposure to SeMet in F1 generation zebrafish. In addition, the study investigated potential underlying mechanisms of SeMet-induced developmental toxicities in early life stages of zebrafish using embryo microinjection. Two separate dietary SeMet exposure studies in adult zebrafish and two in ovo SeMet maternal transfer studies in F1 generation zebrafish were conducted. The first dietary or in ovo exposure study explored effects of excess SeMet exposure on adult zebrafish or the entire life cycle of F1 generation zebrafish. The second study investigated mechanisms of observed SeMet-induced effects on adult or F1 generation zebrafish. In the first feeding study, a significant reduction in Ucrit and greater accumulation of stored energy were observed in the excess dietary SeMet exposed groups when compared to the Se-sufficient dietary control group. The second feeding study showed a greater metabolic rate, and impaired aerobic energy metabolism and triglyceride homeostasis in adult fish fed excess dietary SeMet, which was associated with a reduction in swimming performance and accumulation of triglycerides. Embryos collected from adult zebrafish in both dietary SeMet exposure studies were used to investigate effects of in ovo SeMet exposure on the entire life cycle of F1 generation fish. The first study showed a greater incidence of mortality, an increasing trend for deformities in F1 generation larval zebrafish, and reduced Ucrit in F1 generation adult fish exposed to excess SeMet via in ovo maternal transfer. However, concentrations of stored energy, cortisol and reproduction were unaltered. The second study found that impaired aerobic performance might have been responsible for the reduction in Ucrit of F1 generation adult zebrafish exposed to excess SeMet. Since there is a high variability in Se deposition among eggs via natural maternal transfer, SeMet embryo microinjection was adopted to mimic maternal transfer and to investigate potential mechanisms of SeMet-induced developmental toxicities in early life stages of zebrafish. Greater gene expression of oxidant-inducible transcription factors and impairment in gene expression of an enzyme involved in methionine catabolism were observed in early life stages of zebrafish exposed to excess SeMet via in ovo microinjection. The research presented in this thesis suggests that environmentally relevant dietary SeMet exposure can alter physiological responses in adult fishes and reduce survivability of F1generation fishes, which could impact fitness and recruitment of wild fishes inhabiting Se-contaminated aquatic ecosystems. In addition, the study suggests that SeMet-induced developmental toxicities in early life stages of fishes might be related to oxidative stress or impaired methylation, or a combination of these mechanisms.

No description available.

Selenium (Se) is a contaminant of potential concern in aquatic systems due to its efficient incorporation into food webs, potential for bioaccumulation at higher trophic levels, and role as a developmental toxicant in oviparous vertebrates. While the presence of embryonic/larval deformities due to in ovo Se exposure is considered the most sensitive toxicological endpoint, elevated levels of dietary Se have also been associated with alterations to bioenergetic and hormonal status of adult female fishes, which consequently could lead to diminished fitness and impaired reproduction. Adverse reproductive effects in fishes have been the primary focus of Se research thus far, while studies focusing on Se toxicity in amphibians in any regard are severely lacking. The US EPA has recently proposed a new set of criteria for the protection of freshwater aquatic life with regards to acceptable Se tissue threshold levels; however, these values were generated based on effects observed in fishes with negligible existent data on amphibians to assist in this process. Thus, the overall goal of this thesis research was to characterize the reproductive and developmental effects of elevated dietary Se exposure in Xenopus laevis, in order to provide a foundation for amphibian related Se research that may assist in establishing effective regulatory guidelines that protect this highly vulnerable and ecologically valuable taxon. The research presented in this thesis was performed as one large generational bioassay with the analysis of experimental variables divided into three sections in order to evaluate the effects of elevated in ovo Se exposure via maternal transfer on early and late stages of larval development in addition to the overall fitness of adult X. laevis females after a dietary exposure. Adult X. laevis females were fed a diet augmented with L-selenomethionine (SeMet) for 68 days after which they were bred with untreated males. The resultant embryos were incubated up to 5 days post fertilization (dpf) to determine fertilization success, hatchability, mortality and frequency/severity of malformations. Subsamples of 5 dpf tadpoles were selected and raised to completion of metamorphosis for evaluation of mortality, growth and maturation rate. In addition, tissue and blood samples as well as morphometric indices were collected from X. laevis females, upon completion of the exposure period and subsequent breeding, to ascertain Se tissue distribution, triglyceride and glycogen levels, cortisol concentrations and the overall health status of SeMet-treated females. Within the data gathered throughout this research, a foundation of knowledge characterizing Se toxicity in amphibians was established along with the development of an early life stage toxicity threshold for the frequency of teratogenic abnormalities in X. laevis. The bioenergetic and stress status in addition to the overall body condition of adult females after a 68 day dietary exposure showed no significant differences among treatment groups. The concentrations of Se measured in the ovary, egg, liver and muscle samples increased with female dietary Se levels with strong positive relationships between egg Se concentrations and the other three tissues being illustrated. Elevated in ovo Se exposure had no biologically significant effect on fertilization success, hatchability or mortality within the first 5 dpf; however, the frequency and severity of morphological abnormalities was significantly greater in tadpoles from the highest dose group, with eye lens abnormalities most prominently observed. Late stage larval survival and growth was unaffected by in ovo Se exposure; however, the distribution of developmental stages observed at the set time point when 50% of tadpoles completed metamorphosis showed a larger portion of tadpoles at earlier stages of development in the highest dose group despite no overall change in time to metamorphosis. The results of this thesis research in its entirety suggest that amphibians, as represented by X. laevis, are potentially more tolerant to elevated in ovo and dietary Se exposures than other oviparous vertebrates studied to date; however, without sufficient data for comparison it is unknown whether X. laevis is a tolerant, average or sensitive species among amphibians.

Orientador: Rodrigo Yudi Fujimoto / Banca: Claudinei da Cruz / Banca: Eduardo Makoto Onaka / Resumo: O Selênio é um mineral constituinte de uma série de enzimas antioxidantes que atuam protegendo as membranas celulares dos danos causados pelo processo de oxidação. Sua deficiência ou excesso na dieta pode resultar em depressão do crescimento e aumento da taxa de mortalidade. O objetivo deste estudo foi avaliar o efeito da suplementação da dieta em jovens de tilápia do Nilo (Oreochromis niloticus) com quatro níveis de selenometionina (0,25; 0,50; 1,0; e 1,5 mg Se/kg) e um grupo controle (0,0 mg Se/kg) no desempenho produtivo (ganho de peso, conversão alimentar aparente, taxa de crescimento específico e consumo de ração), nos índices hepatossomático e esplenossomático, na histopatologia do fígado, no índice de parasitismo por monogenea e na hematologia. O consumo de ração aumentou proporcionalmente ao nível de Se nas dietas. Os índices de desempenho produtivo não apresentaram diferenças significativas, no entanto, as concentrações intermediárias (0,25 e 0,50 mg Se/kg) aumentaram o ganho de peso, diminuíram a conversão alimentar e não apresentaram alterações significativas no estrutura morfofuncional do fígado. Não ocorreu diferença significativa para as variáveis hematológicas estudadas e para o índice de parasitismo por monogenea, porém, observou-se que nos níveis de 0,50 e 1,0 mg Se/kg o número de parasitos foi menor em relação às demais concentrações. Assim, pode-se concluir que a melhor suplementação está entre os níveis de 0,25 e 0,50 mg Se/kg de ração. / Abstract: Selenium is an important micronutrient for animals, essential for the normal life processes. This mineral is a constituent of the enzyme antioxidant glutathione peroxidase, of deiodinase and of thioredoxin reductase. The deficiency or toxic levels in feed can be result in growth depression and mortality. The objective of this study was to evaluate the selenomethionine effects for juveniles Nile tilapia (Oreochromis niloticus) on the growth performance (weight gain, index of alimentary conversion, specific growth rate, diet consumption and index of alimentary efficiency), hepatossomatic and esplenossomatic index, liver histopathology, parasitism and haematology, submitted to four levels of selenium in feed (0.25, 0.50, 1.0, and 1.5 mg Se/kg diet) and control group (0.0 mg Se/kg). The results did not show difference, however, the levels of 0.25 and 0.50 mg Se/kg improve the growth performances evaluated and did not show liver histopathology damage. No differences were observed in haematological parameters. The total count of monogeneans reduced in the levels of 0.50 and 1.0 mg Se/kg of diet but without differences due the elevated coefficient of variation. In conclusion the ideal supplementation level was between 0.25 and 0.50 mg Se/kg. / Mestre

No description available.

Omega-3 polyunsaturated fatty acids can reduce the risk of cardiovascular disease and cancers. Enriching broiler meat opportunities lack research on product quality. The fatty acid (FA) profile of birds fed flaxseed for various periods was analyzed. Another experiment assessed FA profile and oxidation products in frozen-raw and cooked thigh meat in birds fed 20% linPRO (50% extruded flaxseed) with antioxidant combinations. Males deposited more omega-3 in breast meat than females. It required 26.2 d (10%flax) or 11.3 d (17%flax) feeding to achieve the 300 mg omega-3/100g of breast. Eicosapentaenoic and docosahexaenoic acids were deposited in the phospholipids whereas a-linolenic acid associated with triacylglycerols. Oxysterol appearance was reduced in thighs of high vitamin E birds while the high selenium treatment had no effect or even raised oxysterols during roasting. Antioxidants inhibited thiobarbuturic reactive acid substances in stored frozen-raw meat. Stability of omega-3 broiler meat was improved with increased dietary antioxidant levels. / Food Science and Technology

Selenium (Se) is an essential micronutrient, being a component of more than twenty seleno-proteins in humans. Previous studies suggested that increased intake of Se may reduce the risk of degenerative diseases including cancer; however, excessive intake can be toxic. Wheat is one of the major dietary sources of Se in humans, mainly in the form of L-selenomethionine (Se-met) but the impact of this source of Se on human health at the genome level was previously unexplored. This PhD project aimed to (a) determine the safe dose-range and bio-efficacy of Se-met in vitro; (b) identify the optimal concentration of Se-met for reduction of genome damage in vitro; (c) investigate the optimal concentration of Se-met for improving resistance to gamma radiation or hydrogen peroxide induced genome damage in vitro; d) determine the bioavailability and bioefficacy of Se in vivo, in the form of either Semet or wheat biofortified with Se; e) identify the nutrients and food groups that are correlated with Se intake/status and f) identify the nutrients, food groups and plasma mineral concentrations that are correlated to baseline lymphocyte DNA damage. The in vitro study was performed on the peripheral blood lymphocytes isolated from six males and cultured with media supplemented with Se-met in a series of Se concentrations from 3 to 3850 μg Se/l while keeping the total methionine (i.e. Se-met + L-methionine) concentration constant. Baseline genome stability of lymphocytes and the extent of DNA damage induced by 1.5 Gy γ-ray or 7.5 μM hydrogen peroxide (H₂O₂) were investigated using the Cytokinesis-block Micronucleus Cytome (CBMNCyt) assay and the alkaline Comet assay with and without glycosylase (Fpg or Endo III) treatment after 9 days of culture. Results showed that high Se concentrations (≥1880 μg Se/l) caused strong inhibition of cell division, extensive DNA damage and increased cell death indicating cytotoxicity and genotoxicity. Baseline frequency of nucleoplasmic bridges (NPBs) and nuclear buds (NBud) declined significantly as Se concentration increased from 3 μg Se/l to 430 μg Se/l (P trend = 0.03 and 0.008, respectively); however, a significant trend of increase in Comet DNA damage was also observed (P trend <0.05) in lymphocytes. Selenium concentration (≤ 430 μg Se/l) had no significant effect on baseline frequency of micronuclei (MN) or DNA oxidation and had no protective effect against γ-ray-induced or H₂O₂-induced genome damage in lymphocytes. A randomised double-blind placebo-controlled intervention trial was conducted on healthy South Australian males (n = 62, age (mean ± SD) 56 ± 7.0 years) with Se dosage increased every 8 weeks for a total duration of 24 weeks. This study compared the bioavailability, by using plasma Se concentration as the biomarker, and bioefficacy of Se, by using platelet glutathione peroxidase (GPx) activity and lymphocyte DNA damage as biomarkers, from wheat process-fortified with Se-met (PROFORT) and high-Se wheat biofortified with Se (BIOFORT) compared to non-fortified normal (CONTROL) wheat. It was found that increased Se intake from BIOFORT wheat increased plasma Se concentration effectively in a dose-response manner from a baseline of 122 μg/l up to 190 μg/l (P<0.001). Increased Se intake from PROFORT wheat also increased plasma Se with a plateau at 140 μg/l, being therefore less effective than BIOFORT wheat (P<0.001). There was no significant change in Se status in the CONTROL group. Improved plasma Se concentrations had no effect on platelet GPx activity or lymphocyte DNA damage in either of the intervention groups. Results from the food frequency questionnaire (FFQ) survey (n = 173) and plasma Se concentration survey (n = 179) suggested that the study population screened for participation in the in vivo trial described above had a mean plasma Se concentration (± SD) of 102 (± 12) μg/l and a mean (± SD) estimated Se intake of 165 (± 68) μg/d. This is a higher estimated Se intake than found in previous Australian studies. The major dietary sources of Se were found to be bread/cereals, fish/seafood and meat. However, increased intake of nuts/seeds, which are rich in Se, may have undesirable effects on lymphocyte DNA oxidation in this Se-replete population. In conclusion, the in vitro studies suggest that (1) Se-met at higher concentrations at greater or equal to 1880 μg Se/l is cytotoxic; (2) Se-met may improve specific genome stability biomarkers such as nucleoplasmic bridge and nuclear bud at concentrations up to 430 μg Se/l, but further studies are needed to verify this effect. The in vivo studies in older men showed that Se from BIOFORT wheat is more effective in raising plasma Se concentration than Se from wheat process-fortified by the addition of Se-met, when both wheat products were subjected to strong heat. However, the platelet GPx activity and lymphocyte DNA damage appeared not to be modified by improved Se status. This work contains two publications: 1) "The effect of selenium, as selenomethionine, on genome stability and cytotoxicity in human lymphocytes as measured by the cytokinesis-block micronucleus cytome assay". Mutagenesis 2009 May;24(3):225-32. 2) "Increased consumption of wheat biofortified with selenium does not modify biomarkers of cancer risk, oxidative stress or immune function in Australian males" Environmental Molecular Mutagenesis. 2009 July; 50 (6):489-501 The latter one was not able to be published in a journal of higher impact factor due to part of the data had been published elsewhere. Both articles are attached in Appendix. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1523459 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2010

Made available in DSpace on 2014-06-11T19:22:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-07-18Bitstream added on 2014-06-13T19:48:38Z : No. of bitstreams: 1 gomes_gr_me_jabo.pdf: 339770 bytes, checksum: dd4a8375e7eb01472c1aff691990e379 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O Selênio é um mineral constituinte de uma série de enzimas antioxidantes que atuam protegendo as membranas celulares dos danos causados pelo processo de oxidação. Sua deficiência ou excesso na dieta pode resultar em depressão do crescimento e aumento da taxa de mortalidade. O objetivo deste estudo foi avaliar o efeito da suplementação da dieta em jovens de tilápia do Nilo (Oreochromis niloticus) com quatro níveis de selenometionina (0,25; 0,50; 1,0; e 1,5 mg Se/kg) e um grupo controle (0,0 mg Se/kg) no desempenho produtivo (ganho de peso, conversão alimentar aparente, taxa de crescimento específico e consumo de ração), nos índices hepatossomático e esplenossomático, na histopatologia do fígado, no índice de parasitismo por monogenea e na hematologia. O consumo de ração aumentou proporcionalmente ao nível de Se nas dietas. Os índices de desempenho produtivo não apresentaram diferenças significativas, no entanto, as concentrações intermediárias (0,25 e 0,50 mg Se/kg) aumentaram o ganho de peso, diminuíram a conversão alimentar e não apresentaram alterações significativas no estrutura morfofuncional do fígado. Não ocorreu diferença significativa para as variáveis hematológicas estudadas e para o índice de parasitismo por monogenea, porém, observou-se que nos níveis de 0,50 e 1,0 mg Se/kg o número de parasitos foi menor em relação às demais concentrações. Assim, pode-se concluir que a melhor suplementação está entre os níveis de 0,25 e 0,50 mg Se/kg de ração. / Selenium is an important micronutrient for animals, essential for the normal life processes. This mineral is a constituent of the enzyme antioxidant glutathione peroxidase, of deiodinase and of thioredoxin reductase. The deficiency or toxic levels in feed can be result in growth depression and mortality. The objective of this study was to evaluate the selenomethionine effects for juveniles Nile tilapia (Oreochromis niloticus) on the growth performance (weight gain, index of alimentary conversion, specific growth rate, diet consumption and index of alimentary efficiency), hepatossomatic and esplenossomatic index, liver histopathology, parasitism and haematology, submitted to four levels of selenium in feed (0.25, 0.50, 1.0, and 1.5 mg Se/kg diet) and control group (0.0 mg Se/kg). The results did not show difference, however, the levels of 0.25 and 0.50 mg Se/kg improve the growth performances evaluated and did not show liver histopathology damage. No differences were observed in haematological parameters. The total count of monogeneans reduced in the levels of 0.50 and 1.0 mg Se/kg of diet but without differences due the elevated coefficient of variation. In conclusion the ideal supplementation level was between 0.25 and 0.50 mg Se/kg.

A nutrição para matrizes de frangos de corte tem como objetivo maximizar a produção de ovos e a qualidade da progênie subsequente e é considerada essencial para a melhora da produção e qualidade dos ovos. Os nutrientes transferidos para os ovos são importantes para o crescimento e desenvolvimento fisiológico do embrião. O organismo animal sofre constantemente ação do estresse oxidativo e o selênio (Se) é considerado um eficiente antioxidante natural que é essencial para matrizes de frangos de corte. Este estudo foi conduzido com matrizes de frango de corte alimentadas com duas fontes de Se (selenometionina - orgânica e selenito de sódio - inorgânico) para avaliar o seu desempenho produtivo, as características reprodutivas, a concentração de Se no ovo bem como o desempenho e rendimento de carcaça da progênie subsequente. Foram utilizadas 216 matrizes AP95 Aviagen de 55 a 65 semanas de idade, em delineamento inteiramente casualizado, com dois tratamentos e 27 repetições de quatro aves cada. Para o experimento com a progênie, foram utilizados 520 pintinhos mistos em delineamento inteiramente casualizado em um fatorial 2 x 2 (duas fontes de Se da dieta das matrizes e duas fontes de Se para dietas de frangos de corte - selenito de sódio e selenometionina) com quatro tratamentos, 13 repetições de 10 aves cada. As matrizes alimentadas com Se orgânico melhoraram a produção de ovos em comparação com o Se inorgânico (p = 0,038; p = 0,044). A concentração do Se no ovo e na clara foi maior para Se orgânico em comparação com o inorgânico (p &lt;0,001; p &lt;0,001). As taxas de fertilidade, bem como mortalidade embrionária, não sofreram efeito significativo ao se comparar as duas fontes. Não foram observadas diferenças entre a altura de albúmen, unidade Haugh e espessura da casca para a qualidade do ovo. O peso do ovo e coloração da gema foram estatisticamente diferentes (p=0,001; p=0,026) para fonte inorgânica comprada com a orgânica. A resistência a quebra do ovo foi melhor estatisticamente (p=0,007) para fonte orgânica. Não foram observadas interações entre a dieta da progênie e a dieta materna para nenhum dos critérios avaliados. Não foram observados efeitos da dieta materna, assim como da dieta da progênie sobre o consumo de ração, ganho de peso corporal e rendimento de carcaça e cortes. No entanto, a taxa de conversão alimentar foi melhor (p = 0,017) em frangos de corte provenientes de matrizes alimentadas com selenometiona. Assim, a selenometionina melhorou a produção e qualidade de ovos e propiciou maior transferência de Se para o ovo, principalmente na clara. Além disso, melhorou a conversão alimentar da progênie, devido a sua melhor biodisponibilidade. / The nutrition for broiler breeders has the objective of maximizing egg production and the quality of subsequent progeny. It is essential to improve the egg production and egg quality. The nutrients transferred to the eggs are important for growth and physiological development embryo. The animal organism is constantly suffering by oxidative stress. Selenium (Se) is considered an efficient natural antioxidant and has shown to be essential for broiler breeders. This trial was conducted using broiler breeders fed with two different sources of Se (organic - selenomethionine and inorganic - sodium selenite) to determinate performance, reproductive characteristics, Se concentration in egg as well as performance and carcass yield of the subsequent progeny. It was used 216 AP95 Aviagen broiler breeders, from 55 to 65 weeks of age, in completely randomized design with two treatments and 27 replications of four birds each. For subsequent progeny, it was used 520 straght-run chicks in a completely randomized design in a 2 x 2 factorial (two sources of Se for broiler breeders diets and two sources of Se for broilers diets- sodium selenite and selenomethionine) with four treatments and 13 replications of 10 birds each. Broiler breeders fed with organic Se had improved egg production in comparison to inorganic Se (p=0.038; p=0.044). Se concentration in whole egg and white egg were higher for organic Se in comparison to inorganic Se (p&lt;0.001; p&lt;0.001). The fertility and embryonic mortality were not significant between Se sources. No difference were observed to albumin height, Haugh unit and shell thickness for egg quality. The egg weight and yolk color were statistically different (p = 0.001; p = 0.026) for inorganic source compering to organic. The egg breaking was statistically better (p=0.007) for organic source. For progeny, no interactions between broiler diet and the maternal diet were observed for any of the criteria measured. No effect of maternal diet as well as broiler diet differences were observed on feed intake, body weight gain and carcass yield and cuts. However, feed conversion ratio was improved (p=0,017) in broiler from breeders fed selenomethione. Thus, selenomethionine has improved the egg production and quality, and has been transferred to the egg mainly in the egg white. Also, selenomethionine has improved feed conversion ratio because has a higher bioavailability.

<p>Interaction between mercury and selenium has previously been observed both in man and in animals. The aim of this work was to study expressions of interaction between mercury and selenium in human K-562 cells. Inorganic and organic forms of mercury and selenium were used and cells were either pre-treated with selenium or simultaneously exposed to selenium and mercury. Concentrations of selenium and mercury chosen were indicated by a study of growth inhibition in the individual compounds: a low concentration of selenium and selenomethionine induced slight cell growth inhibition, while a high concentration resulted in a notable growth inhibition. Two mercury concentrations were chosen: one with minimal toxicity and another with high cell toxicity. In addition, uptake and retention patterns of selenomethionine and selenite differed in both selenocompounds.</p><p>All simultaneous treatments with 3.5 μM methylmercury produced a reduction in cellular mercury with increased selenium concentration. This was particularly obvious in selenite treatments. Growth curves from the simultaneous 3.5 μM methylmercury and selenite treatments indicated protection with increased selenite concentrations. In both exposure protocols, the 5 μM methylmercury treatments were toxic to the cells. </p><p>In both study protocols, cells exposed to selenite and mercuric chloride manifested increased cellular mercury uptake with increased selenium concentration. In all selenite and 35 μM mercuric chloride treatments, no inhibition of growth was observed, while the 50 μM mercuric chloride treatments were toxic to the cells. Selenite-dependent protection was achieved in both exposure protocols when considering the cellular uptake of mercury. With few exceptions, selenomethionine produced similar effects as selenite on mercuric chloride uptake and growth inhibition.</p>