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Fumonisin toxicity in ducks and turkeys / Toxicité de la fumonisine chez les canard et les dindesBenlashehr, Imad 18 December 2013 (has links)
Les fumonisines (FBs) sont les principales mycotoxines produites par Fusarium verticillioides et Fusarium proliferatum, qui se retrouvent partout dans le monde dans le maïs et ses produits dérivés. Les doses toxiques et les signes cliniques de toxicité provoqués par les FBs varient dune espèce à lautre. La toxicité des FBs est généralement liée à leur capacité à bloquer le métabolisme des sphingolipides chez les espèces animales, y compris chez les espèces aviaires. De précédentes études ont démontré que les canards présentent une plus grande sensibilité à la toxicité des FBs que les dindes, alors que laccumulation de sphinganine (Sa) dans les tissues est plus importante chez les dindes que chez les canards. Lobjectif de nos travaux était de comprendre les différences de toxicité entre les dindes et les canards los dune exposition aux FBs. Les trois hypothèses suivantes ont été explorées : i) La toxicocinétique de la fumonisine B2 chez les dindes et les canards. ii) La capacité des cellules aviaires à se protéger de limportante accumulation de sphingolipides libres en augmentant leur catabolisme (phosphorylation). iii) Des mécanismes de toxicité des FBs autre que leur altération via le métabolisme des sphingolipides (stress oxydatif et les réponses inflammatoires). Lanalyse des paramètres de toxicocinétique de la fumonisine B2 na pas mis en évidence de différence significative entre les dindes et les canards. Les mesures de la toxicité simultanée de plusieurs FBs chez les dindes et les canards ont confirmé la forte sensibilité des canards. Laccumulation de shingasine-1-phosphate (Sa1P) dans le foie a également été corrélée avec la quantité de Sa mais pas avec les paramètres hépatiques de toxicité. De plus cette étude a mis en évidence que la quantité de Sa dans le foie était fortement dépendante de la teneur en FBs. Cependant les FBs nont eu aucun effet sur les paramètres de stress oxydatif pour les deux espèces. De manière intéressante, les FBs ont eu une légère réponse inflammatoire chez les canards mais pas chez les dindes. Des investigations plus poussées sur les effets des FBs sur le métabolisme des céramides et sur les processus inflammatoires seraient nécessaires pour comprendre les différences de toxicité entre les dindes et les canards exposés aux FBs. / Fumonisins (FBs) are the major mycotoxins produced by Fusarium verticillioides and Fusarium proliferatum, which are found worldwide in maize and maize products. FBs toxic dose and clinical signs of toxicity vary from one species to another. FBs toxicity is commonly linked to their ability on blocking sphingolipids metabolism in all animal species, including avian species. Previous studies have demonstrated that ducks exhibit higher sensitivity to FBs toxicity than turkeys, whereas, the accumulation of sphinganine (Sa) in tissues is more pronounced in turkeys than in ducks. The objectives of our works were to investigate the causes which lead to different toxicity between ducks and turkeys to FBs exposure. The following three hypotheses were investigated: i) Toxicokinetics of fumonisin B2 in ducks and turkeys. ii) Ability of bird cells to protect themselves against high accumulation of free sphingolipids by increasing their catabolism (phosphorylation). iii) Other toxicity mechanisms of FBs rather than their alteration of sphingolipids metabolism (oxidative stress damage and inflammatory responses). The analysis of toxicokinetic parameters of fumonisin B2 did not provide a significant difference between ducks and turkeys. The measurement of simultaneous toxicity of FBs in ducks and turkeys confirmed higher sensibility of ducks. Also the accumulation of Sphingasine-1-Phosphate (Sa1P) in the liver correlated with the amount of Sa but not parameters of hepatic toxicity. Moreover, this study revealed that the amount of Sa in the liver was strongly dependent on the amount of FBs. On the other hand, FBs had no effect on oxidative damages parameters in both species. Interestingly, FBs had mild inflammatory response effect in ducks but not in turkeys. Further investigation on the effects of FBs on ceramide metabolism and inflammatory processes would be necessary to understand the different toxicity between ducks and turkeys to FBs exposure.
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Effets écotoxicologiques de nanoparticules de dioxyde de cérium en milieu aquatique : d’une évaluation en conditions monospécifiques à l’étude de chaînes trophiques expérimentales en microcosme / Ecotoxicological effects of cerium dioxide nanoparticles in freshwater ecosystems : from an evaluation in monospecific conditions to the study of experimental trophic chains in microcosmBour, Agathe 08 January 2015 (has links)
L’écotoxicité de nanoparticules de dioxyde de cérium (CeO2 NP) en milieu dulçaquicole a été évaluée à l’aide (i) d’essais monospécifiques standardisés et (ii) de chaînes trophiques expérimentales exposées en microcosme. Aucune toxicité n’a été observée chez Nitzschia palea et Chironomus riparius en conditions monopsécifiques. Une inhibition de croissance a été observée chez les amphibiens Xenopus laevis et Pleurodeles waltl., ainsi qu’une toxicité aiguë chez le xénope et une génotoxicité dose-dépendante chez le pleurodèle. Les expositions en microcosme ont mis en évidence une toxicité aiguë chez le pleurodèle, des modifications des communautés bactériennes, une diminution de la décomposition de la litière, ainsi que des effets tératogènes chez le chironome. Les effets observés varient suivant la nature des CeO2 NP étudiées. L’utilisation d’un système biologique complexe permet l’étude des mécanismes de toxicité dans des conditions plus représentatives des conditions environnementales. / The ecotoxicity of cerium dioxide nanoparticles (CeO2 NPs) was studied on freshwater organisms (i) in standardized monospecific conditions and (ii) on experimental trophic chains exposed in microcosms. No toxicity was observed on Nitzschia palea and Chironomus riparius in monospecific conditions. Growth inhibition was observed on the amphibian species Xenopus laevis and Pleurodeles waltl., as well as acute toxicity and dose-dependent genotoxicity observed on Xenopus and Pleurodeles, respectively. Microcosm experiments revealed acute effects on Pleurodeles, changes in bacterial communities, a decrease in leaf litter decomposition and teratogenicity on chironomids. The observed effects vary depending on the type of CeO2 NPs. The use of complex biological system enables the study of toxicity mechanisms in environmentally relevant conditions.
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Assessment of zebrafish embryo toxicity of environmentally relevant antibioticsMastrangeli, Ophelia January 2021 (has links)
Antibiotics are essential drugs in modern medicine. After consumption antibiotics are excreted in unmetabolized form in the urine and reach our sewage treatment plants (STP). STP are not able to degrade all antibiotics leading to release of antibiotics into the aquatic environment. Aquatic animals are thus continuously exposed to antibiotics. This study involved assessment of the toxicity of eight antibiotics previously detected in the river Fyrisån, Uppsala, Sweden, in developing zebrafish (Danio rerio) embryos up to day six of age. The experiments included assessment of embryonal toxicity for the individual antibiotics as well as mixtures of all antibiotics. The mixtures were based on previously measured concentrations in river Fyrisån and tested in increasing concentrations up to 1000-times higher concentrations. In the toxicity assessment different lethal and sublethal endpoints were observed, such as early movements, heart rate, hatching time and length. These experiments were followed by behaviour study observing the swimming activity during alternating dark-light alternations. Lastly, a bioaccumulation study was performed on mixtures of antibiotics to determine if these antibiotics were bioaccumulative in zebrafish embryos. The results showed that these eight antibiotics, individually and as a mixture did not affect any of the endpoints. As for bioaccumulation, none of the eight antibiotics were bioaccumulating in zebrafish embryos. These antibiotics seem to be non-toxic during fish embryonal development. However, the results cannot determine the long-term effects of antibiotic exposure and thus further studies are needed to assess the potential toxicity of environmentally present antibiotics to fish.
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Assessment of toxicity of almond insecticide-fungicide-adjuvant treatments applied on adult honey bees at field relevant concentrationsWalker, Emily K. January 2021 (has links)
No description available.
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In silico and in vitro Toxicity Study of Two Novel Compounds that Exhibit Promising Therapeutic PotentialSteen, Kayla M. 23 September 2019 (has links)
No description available.
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Understanding the role of superoxide in mediating the teratogenicity of hydroxyureaLarouche, Geneviève. January 2008 (has links)
No description available.
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Toxicity of Food-Relevant Nanoparticles in Intestinal Epithelial ModelsMcCracken, Christie Joy 01 October 2015 (has links)
No description available.
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DNA barcoding of different earthworms' species and their response to ecotoxicological testing / Laetitia Voua OtomoVoua Otomo, Laetitia January 2015 (has links)
The ecotoxicological literature reveals that countless researchers worldwide rely upon informally
identified commercial earthworm stocks for laboratory bioassays. The primary aim of this study
was to investigate laboratory and commercial stocks of Eisenia species used in South Africa in
order to confirm their taxonomy, assess their levels of genetic richness and differentiation. To do
so, populations of potential Eisenia andrei and Eisenia fetida were purchased/obtained from
vermiculturists and laboratories from four provinces of South Africa. DNA barcoding was used to
investigate these taxonomic uncertainties. The COI gene was partially amplified and sequenced
in selected earthworms from eight local populations (focal groups) and two European laboratory
stocks (non-focal groups). Only nine COI haplotypes were identified from the 224 sequences
generated. One of these haplotypes was found to belong to the Megascolecidae Perionyx
excavatus. The remaining eight haplotypes belonged to the genus Eisenia although only a
single Eisenia fetida haplotype, represented by six specimens, was found in one of the
European populations. The other seven haplotypes, all occurring in South Africa, were Eisenia
andrei. No Eisenia fetida was found in the South African based populations. One of the
commercial stocks from South Africa and a laboratory culture from Europe were mixes of E.
andrei - P. excavatus and E. andrei – E. fetida respectively. COI haplotype numbers were
limited to two to three distinct sequences within each of the local groups. This translated into a
haplotype diversity (H) lower than 0.45 in all the populations, which is very low when compared
to other such earthworm studies in which COI polymorphism has been investigated. Of all the
local populations investigated, only the lone field population included was genetically divergent
from the other populations. This was explained by the haplotype distribution across the
populations which indicated that this population was the only one not harbouring the haplotype
which represented 75% or more of the COI sequences within the local populations. Because
research suggests that earthworm populations with limited genetic diversity may suffer
inbreeding depression which could affect traits such as reproduction and survival, the
secondary aim was to test whether metal-sensitive earthworms were overly present in the
populations investigated. To do so, the three most common COI haplotypes identified between
the 8 local populations of E. andrei (called Hap1, Hap2 and Hap3) were paired up and exposed
to cadmium. A total of six couples were exposed to 0, 25, 50 and 100 mg Cd/kg for 4 weeks at
20ºC. The survival, biomass variation, cocoon production and cocoon hatching success were
assessed for all the couples. The results indicated that couple 6 (Hap3xHap3) was the most
sensitive for three of the endpoints assessed whereas couple 4 (Hap1 x Hap3) was the least
sensitive. Cocoon hatching success could not help differentiate the couples. The analysis of Cd
tissue contents revealed that with increasing Cd concentration, Cp6 (Hap3xHap3) could
accumulate significantly more Cd than any other couple (p ≤ 0.01). These findings indicate that
earthworm populations may carry intrinsically metal-tolerant and metal-sensitive genotypes. In
the context of ecotoxicological testing, the present results underline the importance of using
genetically diverse populations in laboratory testing as Cp6 (Hap3xHap3) could have suffered
from the deleterious effect of inbreeding. Because E. fetida could not be found in the local
populations assessed, it is recommended that further earthworm DNA barcoding studies,
covering a more representative geographical area of South Africa and including more field
populations of Eisenia spp. be conducted. Because of the occurrence of genetic homogeneity in
the populations studied, it is suggested that captive breeding initiatives be established using
specimens obtained from several geographically distant field and reared populations. Further
research investigating patterns of Cd accumulation/excretion kinetics between the Cd-tolerant
and Cd-sensitive individuals reported in the present study, should be conducted to help
determine whether inbreeding is the sole factor explaining the observed genotypic responses to
Cd. Finally, the necessity of a standardised earthworm barcoding protocol that could help both
to properly identify laboratory earthworm stocks and to select genetically diverse stocks suitable
for laboratory testing, is discussed together with the relevance of the present work to
ecotoxicological testing in general. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
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DNA barcoding of different earthworms' species and their response to ecotoxicological testing / Laetitia Voua OtomoVoua Otomo, Laetitia January 2015 (has links)
The ecotoxicological literature reveals that countless researchers worldwide rely upon informally
identified commercial earthworm stocks for laboratory bioassays. The primary aim of this study
was to investigate laboratory and commercial stocks of Eisenia species used in South Africa in
order to confirm their taxonomy, assess their levels of genetic richness and differentiation. To do
so, populations of potential Eisenia andrei and Eisenia fetida were purchased/obtained from
vermiculturists and laboratories from four provinces of South Africa. DNA barcoding was used to
investigate these taxonomic uncertainties. The COI gene was partially amplified and sequenced
in selected earthworms from eight local populations (focal groups) and two European laboratory
stocks (non-focal groups). Only nine COI haplotypes were identified from the 224 sequences
generated. One of these haplotypes was found to belong to the Megascolecidae Perionyx
excavatus. The remaining eight haplotypes belonged to the genus Eisenia although only a
single Eisenia fetida haplotype, represented by six specimens, was found in one of the
European populations. The other seven haplotypes, all occurring in South Africa, were Eisenia
andrei. No Eisenia fetida was found in the South African based populations. One of the
commercial stocks from South Africa and a laboratory culture from Europe were mixes of E.
andrei - P. excavatus and E. andrei – E. fetida respectively. COI haplotype numbers were
limited to two to three distinct sequences within each of the local groups. This translated into a
haplotype diversity (H) lower than 0.45 in all the populations, which is very low when compared
to other such earthworm studies in which COI polymorphism has been investigated. Of all the
local populations investigated, only the lone field population included was genetically divergent
from the other populations. This was explained by the haplotype distribution across the
populations which indicated that this population was the only one not harbouring the haplotype
which represented 75% or more of the COI sequences within the local populations. Because
research suggests that earthworm populations with limited genetic diversity may suffer
inbreeding depression which could affect traits such as reproduction and survival, the
secondary aim was to test whether metal-sensitive earthworms were overly present in the
populations investigated. To do so, the three most common COI haplotypes identified between
the 8 local populations of E. andrei (called Hap1, Hap2 and Hap3) were paired up and exposed
to cadmium. A total of six couples were exposed to 0, 25, 50 and 100 mg Cd/kg for 4 weeks at
20ºC. The survival, biomass variation, cocoon production and cocoon hatching success were
assessed for all the couples. The results indicated that couple 6 (Hap3xHap3) was the most
sensitive for three of the endpoints assessed whereas couple 4 (Hap1 x Hap3) was the least
sensitive. Cocoon hatching success could not help differentiate the couples. The analysis of Cd
tissue contents revealed that with increasing Cd concentration, Cp6 (Hap3xHap3) could
accumulate significantly more Cd than any other couple (p ≤ 0.01). These findings indicate that
earthworm populations may carry intrinsically metal-tolerant and metal-sensitive genotypes. In
the context of ecotoxicological testing, the present results underline the importance of using
genetically diverse populations in laboratory testing as Cp6 (Hap3xHap3) could have suffered
from the deleterious effect of inbreeding. Because E. fetida could not be found in the local
populations assessed, it is recommended that further earthworm DNA barcoding studies,
covering a more representative geographical area of South Africa and including more field
populations of Eisenia spp. be conducted. Because of the occurrence of genetic homogeneity in
the populations studied, it is suggested that captive breeding initiatives be established using
specimens obtained from several geographically distant field and reared populations. Further
research investigating patterns of Cd accumulation/excretion kinetics between the Cd-tolerant
and Cd-sensitive individuals reported in the present study, should be conducted to help
determine whether inbreeding is the sole factor explaining the observed genotypic responses to
Cd. Finally, the necessity of a standardised earthworm barcoding protocol that could help both
to properly identify laboratory earthworm stocks and to select genetically diverse stocks suitable
for laboratory testing, is discussed together with the relevance of the present work to
ecotoxicological testing in general. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
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Pre-employment screening practices to prevent the recruitment of psychopaths (antisocial personalities) into South African organisationsMarais, Albert Alexander 24 August 2012 (has links)
A snapshot of the current state of the business world is given, followed by the proposition that people are the root cause of the problems therein. Mutual influence between individual and organisation is depicted. The corporate psychopath is identified as being especially problematic. Therefore measures to prevent the recruitment of psychopaths into organisations will be studied. The objectives of this research report are:
• To establish whether South African organisations are aware of the problems caused by psychopaths.
• To establish what screening processes are in place in South African organisations to identify psychopaths.
• To suggest additional measures that would prevent the recruitment of psychopaths into organisations.
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