Biogenic synthesis of Silver nanoparticles (AgNPs) and its effects on Zebrafish (Danio rerio)
- Authors: Siguba, Busiswa
- Date: 2019
- Subjects: Biogenic synthesis -- Zebrafish , Nanoparticles – Silver , Zebrafish
- Language: English
- Type: Thesis , Masters , M Sc
- Identifier: http://hdl.handle.net/11260/1339 , vital:32260
- Description: The increase in use and production of engineered nanoparticles in recent years points towards their inevitable release into freshwater ecosystems. Subsequently, exposure to organisms in freshwater ecosystems is to be expected. The aim of this dissertation was to synthesize silver nanoparticles (AgNPs) using silver nitrate, gelatine and maltose as precursor, capping and reducing agent respectively. Cytotoxic effects of the as-synthesized AgNPs was evaluated at concentrations of 0.031 μg/L, 0.250 μg/L and 5.000 μg/L on selected target organs in zebrafish (Danio rerio ) after 96 hr of exposure, under a 24 hr static renewal system. Formation of AgNPs was investigated by UV-Vis spectrophotometry, which displayed absorption maxima peak characteristic of plasmon resonance band for silver at 419 nm. From transmission electron microscopy, AgNPs was found to be small, well dispersed and spherical in shape with a narrow size distribution, and an average particle size of3.76 ± 1.00 nm. Histopathological alterations following exposure to AgNPs was noticed in the gills, epidermis, muscle tissue and kidney. Secondary lamellae hypertrophy, oedema and epithelial lifting was observed in all experimental groups. Curling and clubbed tips of secondary lamellae were observed at the lowest concentration (0.031 μg/L). Hyperplasia and lamellae fusion was most common at the median concentration (0.250 μg/L) of AgNP exposure. Hypertrophy of endothelial cells along with blood vessel congestion was also observed. Reduced secondary lamellar length, lamellar erosion and thinning were observed at the highest concentration (5.000 μg/L).AgNP exposure also altered the shape of alarm cells. In addition, hyperplasia and hypertrophy of goblet cells were observed at the highest concentration (5.000 μg/L) at 96 hr. At 5.000 μg/L of AgNP, PAS reaction was intense (deep purple), while the number and size of these cells decreased. Staining with AB pH 2.5 demonstrated an intense deep purple staining at the lowest and at the median concentration (24 hr). Moderate staining was seen at the higher concentrations. Muscle bundles with severe oedema, their thickening and separation were more pronounced in all treated groups. Histopathological tubular deformation and mononuclear cell infiltration were observed in kidney tissues. In addition; an increase in melano‐macrophage aggregation intensity was identified on the 48 hr in the treated groups. An increase in tubular epithelial cell regeneration/ proliferation, resulting in production of new epithelial cells which was indicative of recovering of kidney tissues from AgNP induced injury at 96 hr of exposure. Results presented here shows that fish respond to the presence of AgNPs.
- Full Text:
- Date Issued: 2019
- Authors: Siguba, Busiswa
- Date: 2019
- Subjects: Biogenic synthesis -- Zebrafish , Nanoparticles – Silver , Zebrafish
- Language: English
- Type: Thesis , Masters , M Sc
- Identifier: http://hdl.handle.net/11260/1339 , vital:32260
- Description: The increase in use and production of engineered nanoparticles in recent years points towards their inevitable release into freshwater ecosystems. Subsequently, exposure to organisms in freshwater ecosystems is to be expected. The aim of this dissertation was to synthesize silver nanoparticles (AgNPs) using silver nitrate, gelatine and maltose as precursor, capping and reducing agent respectively. Cytotoxic effects of the as-synthesized AgNPs was evaluated at concentrations of 0.031 μg/L, 0.250 μg/L and 5.000 μg/L on selected target organs in zebrafish (Danio rerio ) after 96 hr of exposure, under a 24 hr static renewal system. Formation of AgNPs was investigated by UV-Vis spectrophotometry, which displayed absorption maxima peak characteristic of plasmon resonance band for silver at 419 nm. From transmission electron microscopy, AgNPs was found to be small, well dispersed and spherical in shape with a narrow size distribution, and an average particle size of3.76 ± 1.00 nm. Histopathological alterations following exposure to AgNPs was noticed in the gills, epidermis, muscle tissue and kidney. Secondary lamellae hypertrophy, oedema and epithelial lifting was observed in all experimental groups. Curling and clubbed tips of secondary lamellae were observed at the lowest concentration (0.031 μg/L). Hyperplasia and lamellae fusion was most common at the median concentration (0.250 μg/L) of AgNP exposure. Hypertrophy of endothelial cells along with blood vessel congestion was also observed. Reduced secondary lamellar length, lamellar erosion and thinning were observed at the highest concentration (5.000 μg/L).AgNP exposure also altered the shape of alarm cells. In addition, hyperplasia and hypertrophy of goblet cells were observed at the highest concentration (5.000 μg/L) at 96 hr. At 5.000 μg/L of AgNP, PAS reaction was intense (deep purple), while the number and size of these cells decreased. Staining with AB pH 2.5 demonstrated an intense deep purple staining at the lowest and at the median concentration (24 hr). Moderate staining was seen at the higher concentrations. Muscle bundles with severe oedema, their thickening and separation were more pronounced in all treated groups. Histopathological tubular deformation and mononuclear cell infiltration were observed in kidney tissues. In addition; an increase in melano‐macrophage aggregation intensity was identified on the 48 hr in the treated groups. An increase in tubular epithelial cell regeneration/ proliferation, resulting in production of new epithelial cells which was indicative of recovering of kidney tissues from AgNP induced injury at 96 hr of exposure. Results presented here shows that fish respond to the presence of AgNPs.
- Full Text:
- Date Issued: 2019
The influence of copreneurial relationships on the restaurant industry : a study in the Nelson Mandela Metropole
- Von Hoffman, Ethen Langeford
- Authors: Von Hoffman, Ethen Langeford
- Date: 2012
- Subjects: Couple-owned business enterprises -- Management , Entrepreneurship -- South Africa , Small business -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8839 , http://hdl.handle.net/10948/d1020003
- Description: Entrepreneurship plays an important role in the South African economy, especially in light of the recent global recession. For family businesses, namely copreneurs in the restaurant industry, to be afforded a better opportunity to perform better and be viable and sustainable, a deeper understanding and insight into their dynamics is required. Researching and implementing strategies or recommendations to improve the influence of copreneurial relationships in the restaurant industry is fundamentally important to the growth and sustainability of restaurants in the hospitality industry, in the Nelson Mandela Metropole (NMM). However, no known studies have been performed in this area of copreneurship. This study sought to present exploratory research in the rapidly expanding and critically important sector family business, namely copreneurships specifically in the restaurant industry in the NMM, in South Africa. The primary research objective of this study is to gain a deeper understanding and insight into the influence of copreneurial relationships in the restaurant industry in the NMM. A phenomenological, or qualitative, research paradigm, through the use of focused one-on-one interviews, was employed to probe and analyse relational factors of copreneurial relationships. A qualifying questionnaire was constructed to determine the most effective sample for the study followed by an extensive questionnaire constructed to probe into the demographics and the specifically identified relational factors of the ten qualifying copreneurships. The collected data was then analysed and inferences were derived from the findings of the study. The findings revealed that what restaurant copreneurships perceive to be the most important relationship factors are very closely linked to the relationship factors perceived important to personally work on and improve. Of the relational factors considered for this study, namely: Commitment, communication, conflict, division of labour, emotional attachment, relationship bond, respect, spousal harmony, trust and the spousal values system, several factors stood out as those baring greatest influence on copreneurial relationships and their business. This study, from an analysis of the collected interview data and subsequent findings, determined communication to stand out above all other factors as being the most critical to copreneurial relationships. All other factors emanated as important but division of labour, values system, respect and relationship bond were revealed as extremely important, just behind communication. In light of these findings, as well as the discovery of other affecting factors, the study concluded that the viability and sustainability of restaurant copreneurships is of paramount significance. In order to facilitate this, copreneurial couples must cherish their relationships with each other, understand the dynamics of the relational factors affecting their relationships, invoke relational improvements for their viability and sustainability, not neglect family responsibilities and preservation in light of business needs and work together as a team.
- Full Text:
- Date Issued: 2012
- Authors: Von Hoffman, Ethen Langeford
- Date: 2012
- Subjects: Couple-owned business enterprises -- Management , Entrepreneurship -- South Africa , Small business -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8839 , http://hdl.handle.net/10948/d1020003
- Description: Entrepreneurship plays an important role in the South African economy, especially in light of the recent global recession. For family businesses, namely copreneurs in the restaurant industry, to be afforded a better opportunity to perform better and be viable and sustainable, a deeper understanding and insight into their dynamics is required. Researching and implementing strategies or recommendations to improve the influence of copreneurial relationships in the restaurant industry is fundamentally important to the growth and sustainability of restaurants in the hospitality industry, in the Nelson Mandela Metropole (NMM). However, no known studies have been performed in this area of copreneurship. This study sought to present exploratory research in the rapidly expanding and critically important sector family business, namely copreneurships specifically in the restaurant industry in the NMM, in South Africa. The primary research objective of this study is to gain a deeper understanding and insight into the influence of copreneurial relationships in the restaurant industry in the NMM. A phenomenological, or qualitative, research paradigm, through the use of focused one-on-one interviews, was employed to probe and analyse relational factors of copreneurial relationships. A qualifying questionnaire was constructed to determine the most effective sample for the study followed by an extensive questionnaire constructed to probe into the demographics and the specifically identified relational factors of the ten qualifying copreneurships. The collected data was then analysed and inferences were derived from the findings of the study. The findings revealed that what restaurant copreneurships perceive to be the most important relationship factors are very closely linked to the relationship factors perceived important to personally work on and improve. Of the relational factors considered for this study, namely: Commitment, communication, conflict, division of labour, emotional attachment, relationship bond, respect, spousal harmony, trust and the spousal values system, several factors stood out as those baring greatest influence on copreneurial relationships and their business. This study, from an analysis of the collected interview data and subsequent findings, determined communication to stand out above all other factors as being the most critical to copreneurial relationships. All other factors emanated as important but division of labour, values system, respect and relationship bond were revealed as extremely important, just behind communication. In light of these findings, as well as the discovery of other affecting factors, the study concluded that the viability and sustainability of restaurant copreneurships is of paramount significance. In order to facilitate this, copreneurial couples must cherish their relationships with each other, understand the dynamics of the relational factors affecting their relationships, invoke relational improvements for their viability and sustainability, not neglect family responsibilities and preservation in light of business needs and work together as a team.
- Full Text:
- Date Issued: 2012
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