Helena Taute | University of Pretoria (original) (raw)

Papers by Helena Taute

Research paper thumbnail of Histological analysis of the effects of cadmium, chromium and mercury alone and in combination on the spleen of male Sprague-Dawley rats

Journal of Environmental Science and Health, Part A, 2020

Abstract The mining sector in South Africa is expected to be the fifth largest in the world. Both... more Abstract The mining sector in South Africa is expected to be the fifth largest in the world. Both mining and transport are the most common reasons for an increased risk of human exposure to heavy metal contamination in South Africa. Due to increasing amounts of metals in the environment, this study identified three metals cadmium, chromium and mercury based on the risk of exposure in South Africa. The aim of this study was to investigate the changes in the morphology of the spleen tissue of male Sprague-Dawley rats exposed to these metals alone and in combination by using light microscopy. Forty eight animals in eight experimental groups were exposed, via oral gavage, to these metals at 1000× the World Health Organization’s acceptable water limits of each respective metal, alone and in combination, for 28 days. Changes in the histological structure of the spleen were observed using haematoxylin and eosin and picrosirius red staining. Necrosis was observed in all the groups, with the severity varying between the different exposure groups, alone or in combination. Fibrosis in the spleen tissue was only seen in the experimental groups exposed to cadmium and mercury respectively, as well as in the combination of cadmium and mercury.

Research paper thumbnail of The dual functionality of antimicrobial peptides Os and Os-C in human leukocytes

Journal of Peptide Science, 2019

Antimicrobial peptides (AMPs), Os and Os‐C, have been identified as multifunctional peptides with... more Antimicrobial peptides (AMPs), Os and Os‐C, have been identified as multifunctional peptides with antibacterial, antiendotoxin, and anti‐inflammatory properties. For further development of Os and Os‐C as therapeutic peptides, it is essential to evaluate these effects in human mononuclear (MN) and polymorphonuclear (PMN) leukocytes. The cytotoxicity and the effects of both peptides on MN and PMN morphology were determined with the Alamar‐Blue assay and scanning electron microscopy, respectively. The ability of Os and Os‐C to induce reactive oxygen species (ROS) and to protect against 2,2′‐azobis(2‐amidinopropane) dihydrochloride–induced oxidative damage in both cell populations was evaluated using 2′,7′‐dichlorofluorescin diacetate (DCFH‐DA). Using fluorescently labeled peptides, the ability of the peptides to cross the cell membranes of MN and PMN was also evaluated. At the minimum bactericidal concentrations of Os and Os‐C, neither peptide was cytotoxic. Os caused morphological features of toxicity at 100 μM, entered MN cells, and also protected these cells against oxidative damage. Os‐C caused MN and PMN leukocyte activation associated with ROS formation and was unable to penetrate cell membranes, indicating extracellular membrane interactions. This study confirms that both Os and Os‐C at less than 100 μM are not cytotoxic. The MN‐specific uptake of Os identifies it as a cell‐specific cargo‐carrier peptide, with additional anti‐inflammatory properties. In contrast, the ability of Os‐C to activate MN and PMN cells implies that this peptide should be further evaluated as an AMP, which, in addition to its ability to eradicate infection, can further enhance host immunity. These novel characteristics of Os and Os‐C indicate that these AMPs as peptides can be further developed for specific applications.

Research paper thumbnail of Investigation into the mechanism of action of the antimicrobial peptides Os and Os-C derived from a tick defensin

Peptides, 2015

Highlights • Os and Os-C caused altered intracellular morphology of E. coli and B. subtilis. • Me... more Highlights • Os and Os-C caused altered intracellular morphology of E. coli and B. subtilis. • Membrane effects were observed with fluorescence and TEM studies. • Os and Os-C were able to enter bacterial cells. • The peptides may have intracellular targets such as DNA. • Differences observed between Os and Os-C indicate dissimilar modes of action.

Research paper thumbnail of A descriptive study to provide evidence of the teratogenic and cellular effects of sibutramine and ephedrine on cardiac- and liver-tissue of chick embryos

Microscopy research and technique, Jan 3, 2015

Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influenc... more Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influence normal foetal development. Although the use of drugs during pregnancy should generally be avoided, exposure of the developing foetus to teratogens may occur unknowingly since these compounds may be hidden in products that are being marketed as "all natural." The aim of the current study was to investigate the possible teratogenic and cellular effects of sibutramine-a serotonin-norepinephrine reuptake inhibitor used in the treatment of obesity-on the heart and liver tissue of chick embryos. Ephedrine was used as a positive control. The chick embryo model was chosen because it has been used in studying developmental and experimental biology and teratology with great success. The embryos were exposed to three different concentrations of sibutramine and ephedrine respectively. The results obtained revealed that both compounds exhibited embryotoxicity when compared to the control ...

Research paper thumbnail of Anin ovoinvestigation into the hepatotoxicity of cadmium and chromium evaluated with light- and transmission electron microscopy and electron energy-loss spectroscopy

Journal of Environmental Science and Health, Part A, 2015

Excessive agriculture, transport and mining often lead to the contamination of valuable water res... more Excessive agriculture, transport and mining often lead to the contamination of valuable water resources. Communities using this water for drinking, washing, bathing and the irrigation of crops are continuously being exposed to these heavy metals. The most vulnerable is the developing fetus. Cadmium (Cd) and chrome (Cr) were identified as two of the most prevalent heavy metal water contaminants in South Africa. In this study, chicken embryos at the stage of early organogenesis were exposed to a single dosage of 0.430 mM physiological dosage (PD) and 430 mM(£1000 PD) CdCl 2 , as well as 0.476 mM (PD) and 746 mM(£1000 PD) K 2 Cr 2 O 7. At day 14, when all organ systems were completely developed, the embryos were terminated and the effect of these metals on liver tissue and cellular morphology was determined with light-and transmission electron microscopy (TEM). The intracellular localization of these metals was determined using electron energy-loss spectroscopy (EELS). With light microscopy, the PD of both Cd and Cr had no effect on liver tissue or cellular morphology. At £1000 PD both Cd and Cr caused sinusoid dilation and tissue necrosis. With TEM analysis, Cd exposed hepatocytes presented with irregular chromatin condensation, ruptured cellular membranes and damaged or absent organelles. In contrast Cr caused only slight mitochondrial damage. EELS revealed the bio-accumulation of Cd and Cr along the cristae of the mitochondria and chromatin of the nuclei.

Research paper thumbnail of An In Ovo Investigation of the Ultrastructural Effects of the Heavy Metals Cadmium and Chromium on Liver Tissue

Microscopy and Microanalysis, 2014

Many heavy metals are essential for human biological functions, but some heavy metals, especially... more Many heavy metals are essential for human biological functions, but some heavy metals, especially at high concentrations, can have toxic, carcinogenic and/or teratogenic effects in humans. South Africa is the world's largest reserve of minerals and due to extensive mining activity, air and water pollution occurs [1, 2]. Metal exposure occurs mostly through the ingestion of contaminated water; used for drinking, cooking and for agricultural purposes [3]. In this study the effect of heavy metals, cadmium (Cd) and chromium (Cr) were evaluated due to the high risk of exposure in South Africa. In recent studies, high levels of Cd and Cr were found in rivers and dams in several provinces in South Africa [4-6]. The most vulnerable population to be affected by heavy metal exposure is pregnant women with developing embryos and young children living in rural communities. In the human body, Cd and Cr are metabolized differently, but the consequences are similar namely oxidative stress that leads to DNA damage, apoptosis and lipid peroxidation [7-9]. Thus, the purpose of this study was to evaluate the ultrastructural effects of Cd and Cr on liver tissue by using the in ovo model. Analytical techniques energy dispersive spectroscopy (EDS) and electron energy-loss spectroscopy (EELS) were used to confirm the presence of these metals in liver tissue.

Research paper thumbnail of Premature Collagen Fibril Formation, Fibroblast-Mast Cell Interactions and Mast Cell-Mediated Phagocytosis of Collagen in Keloids

Ultrastructural Pathology, 2015

Keloids are benign hyper-proliferative growths of fibrous tissue, where increased fibroblast acti... more Keloids are benign hyper-proliferative growths of fibrous tissue, where increased fibroblast activity results in abnormal collagen deposition. Excessive inflammation is a characteristic feature of keloids but little is known about the underlying ultrastructural features of keloids related to collagen processing, fibril and fibre formation, the interaction between fibroblasts and associated collagen fibres and mast cells. In this study, the ultrastructure of the dermis of keloid patients was evaluated using light and transmission electron microscopy techniques. Abnormal intracellular premature collagen fibril formation was observed. Phagocytosis of collagen fibrils by mast cells was a common ultrastructural feature of keloid tissue as was a close or direct 2 association between fibroblasts and mast cells. Based on these findings and recent advances in knowledge related to collagen synthesis, fibril formation and processing we hypothesise that keloid formation is primary due to abnormal collagen synthesis where the consequent accumulation of collagen fibres causes increased mast cell recruitment and collagen phagocytosis. Subsequent release of mast cell derived mediators then promotes further collagen synthesis. The observation of early formation in keloid tissue of premature insoluble collagen fibrils supports previous studies that enzymes such as procollagen C-proteinase are important early therapeutic targets.

Research paper thumbnail of Feasibility of high pressure freezing with freeze substitution after long-term storage in chemical fixatives

Microscopy Research and Technique, 2013

Fixation of biological samples is an important process especially related to histo-logical and ul... more Fixation of biological samples is an important process especially related to histo-logical and ultrastructural studies. Chemical fixation was the primary method of fixing tissue for transmission electron microscopy for many years, as it provides adequate preservation of the morphology of cells and organelles. High pressure freezing (HPF) and freeze substitution (FS) is a newer alternative method that rapidly freezes non-cryoprotected samples that are then slowly heated in the FS medium, allowing penetration of the tissue to insure adequate fixation. This study addresses several issues related to tissue preservation for electron microscopy. Using mice liver tissue as model the difference between samples fixed chemically or with HPF immediately after excision, or stored before chemical or HPF fixation were tested with specific focus on the nuclear membrane. Findings are that immediate HPF is the method of choice compared to chemical fixation. Of the chemical fixatives, immediate fixation with 2.5% glutaraldehyde (GA)/form-aldehyde (FA) is the best in preserving membrane morphology, 2.5% GA can be used as alternative for stored and then chemically processed samples, with 10% formalin being suitable as a storage medium only if followed by HPF fixation. Overall, storage leads to lower ultrastructural preservation, but HPF with FS can minimize these artifacts relative to other processing protocols.

Research paper thumbnail of Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi

Journal of Peptide Science, 2013

Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a Signature __________________________... more Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a Signature __________________________________ Date 06/02/2014 © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a 2.4 Circular dichroism secondary structure determination 2.5 3-Dimentional structure construction 2.6 Antibacterial activity assays 2.6.1 Micro-dilution broth assay 2.6.2 Colony forming unit assay 2.6.3 Turbidity assays 2.7 SYTOX Green assay 2.7.1 Preliminary SYTOX green experiments 2.7.2 Optimising the bacterial concentration 2.7.3 Minimum bactericidal concentration determination of peptides in the presence of an increased bacterial concentration 2.7.4 Time study with SYTOX Green fluorescence 2.7.5 Effects of EDTA and Triton X-100 addition on SYTOX Green fluorescence of Gram-positive bacterial strains 2.8 Plasmid binding assay 2.9 Cytotoxicity 2.10 Data and statistical analysis Chapter 3: Results 3.1 Peptide characterisation 3.2 3-Dimentional structure modelling 3.3 Antibacterial activities of synthetic peptides 3.3.1 Determination of minimum inhibitory and minimum bactericidal concentrations 3.3.2 Determination minimum bactericidal concentrations by the CFU method 3.4 Effects of salt and serum on antibacterial activity © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a iii 3.5 Killing kinetics 3.6 Membrane permeabilisation studies 3.7 Plasmid binding properties of Os and Os-C 3.8 Cytotoxicity Chapter 4: Discussion Chapter 5: Conclusion and references © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a

Research paper thumbnail of A descriptive study to provide evidence of the teratogenic and cellular effects of sibutramine and ephedrine on cardiac- and liver-tissue of chick embryos

Microscopy research and technique, Jan 3, 2015

Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influenc... more Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influence normal foetal development. Although the use of drugs during pregnancy should generally be avoided, exposure of the developing foetus to teratogens may occur unknowingly since these compounds may be hidden in products that are being marketed as "all natural." The aim of the current study was to investigate the possible teratogenic and cellular effects of sibutramine-a serotonin-norepinephrine reuptake inhibitor used in the treatment of obesity-on the heart and liver tissue of chick embryos. Ephedrine was used as a positive control. The chick embryo model was chosen because it has been used in studying developmental and experimental biology and teratology with great success. The embryos were exposed to three different concentrations of sibutramine and ephedrine respectively. The results obtained revealed that both compounds exhibited embryotoxicity when compared to the control ...

Research paper thumbnail of An in ovo investigation into the hepatotoxicity of cadmium and chromium evaluated with light- and transmission electron microscopy and electron energy-loss spectroscopy

Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering

Excessive agriculture, transport and mining often lead to the contamination of valuable water res... more Excessive agriculture, transport and mining often lead to the contamination of valuable water resources. Communities using this water for drinking, washing, bathing and the irrigation of crops are continuously being exposed to these heavy metals. The most vulnerable is the developing fetus. Cadmium (Cd) and chrome (Cr) were identified as two of the most prevalent heavy metal water contaminants in South Africa. In this study, chicken embryos at the stage of early organogenesis were exposed to a single dosage of 0.430 μM physiological dosage (PD) and 430 μM (×1000 PD) CdCl2, as well as 0.476 μM (PD) and 746 μM (×1000 PD) K2Cr2O7. At day 14, when all organ systems were completely developed, the embryos were terminated and the effect of these metals on liver tissue and cellular morphology was determined with light- and transmission electron microscopy (TEM). The intracellular localization of these metals was determined using electron energy-loss spectroscopy (EELS). With light microscop...

Research paper thumbnail of Premature Collagen Fibril Formation, Fibroblast-Mast Cell Interactions and Mast Cell-Mediated Phagocytosis of Collagen in Keloids

Ultrastructural Pathology, 2015

Abstract Keloids are benign hyper-proliferative growths of fibrous tissue where increased fibrobl... more Abstract Keloids are benign hyper-proliferative growths of fibrous tissue where increased fibroblast activity results in abnormal collagen deposition. Excessive inflammation is a characteristic feature of keloids, but little is known about the underlying ultrastructural features of keloids related to collagen processing, fibril and fiber formation, the interaction between fibroblasts and associated collagen fibers and mast cells. In this study, the ultrastructure of the dermis of keloid patients was evaluated using light and transmission electron microscopy techniques. Abnormal intracellular premature collagen fibril formation was observed. Phagocytosis of collagen fibrils by mast cells was a common ultrastructural feature of keloid tissue as was a close or direct association between fibroblasts and mast cells. Based on these findings and recent advances in knowledge related to collagen synthesis, fibril formation and processing, we hypothesize that keloid formation is primarily due to abnormal collagen synthesis where the consequent accumulation of collagen fibers causes increased mast cell recruitment and collagen phagocytosis. Subsequent release of mast cell-derived mediators then promotes further collagen synthesis. The observation of early formation in keloid tissue of premature insoluble collagen fibrils supports previous studies that enzymes such as procollagen C-proteinase are important early therapeutic targets.

Research paper thumbnail of Feasibility of high pressure freezing with freeze substitution after long-term storage in chemical fixatives

Microscopy Research and Technique, 2013

Fixation of biological samples is an important process especially related to histological and ult... more Fixation of biological samples is an important process especially related to histological and ultrastructural studies. Chemical fixation was the primary method of fixing tissue for transmission electron microscopy for many years, as it provides adequate preservation of the morphology of cells and organelles. High pressure freezing (HPF) and freeze substitution (FS) is a newer alternative method that rapidly freezes non-cryoprotected samples that are then slowly heated in the FS medium, allowing penetration of the tissue to insure adequate fixation. This study addresses several issues related to tissue preservation for electron microscopy. Using mice liver tissue as model the difference between samples fixed chemically or with HPF immediately after excision, or stored before chemical or HPF fixation were tested with specific focus on the nuclear membrane. Findings are that immediate HPF is the method of choice compared to chemical fixation. Of the chemical fixatives, immediate fixation with 2.5% glutaraldehyde (GA)/formaldehyde (FA) is the best in preserving membrane morphology, 2.5% GA can be used as alternative for stored and then chemically processed samples, with 10% formalin being suitable as a storage medium only if followed by HPF fixation. Overall, storage leads to lower ultrastructural preservation, but HPF with FS can minimize these artifacts relative to other processing protocols.

Research paper thumbnail of Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi

Journal of Peptide Science, 2013

Research paper thumbnail of Histological analysis of the effects of cadmium, chromium and mercury alone and in combination on the spleen of male Sprague-Dawley rats

Journal of Environmental Science and Health, Part A, 2020

Abstract The mining sector in South Africa is expected to be the fifth largest in the world. Both... more Abstract The mining sector in South Africa is expected to be the fifth largest in the world. Both mining and transport are the most common reasons for an increased risk of human exposure to heavy metal contamination in South Africa. Due to increasing amounts of metals in the environment, this study identified three metals cadmium, chromium and mercury based on the risk of exposure in South Africa. The aim of this study was to investigate the changes in the morphology of the spleen tissue of male Sprague-Dawley rats exposed to these metals alone and in combination by using light microscopy. Forty eight animals in eight experimental groups were exposed, via oral gavage, to these metals at 1000× the World Health Organization’s acceptable water limits of each respective metal, alone and in combination, for 28 days. Changes in the histological structure of the spleen were observed using haematoxylin and eosin and picrosirius red staining. Necrosis was observed in all the groups, with the severity varying between the different exposure groups, alone or in combination. Fibrosis in the spleen tissue was only seen in the experimental groups exposed to cadmium and mercury respectively, as well as in the combination of cadmium and mercury.

Research paper thumbnail of The dual functionality of antimicrobial peptides Os and Os-C in human leukocytes

Journal of Peptide Science, 2019

Antimicrobial peptides (AMPs), Os and Os‐C, have been identified as multifunctional peptides with... more Antimicrobial peptides (AMPs), Os and Os‐C, have been identified as multifunctional peptides with antibacterial, antiendotoxin, and anti‐inflammatory properties. For further development of Os and Os‐C as therapeutic peptides, it is essential to evaluate these effects in human mononuclear (MN) and polymorphonuclear (PMN) leukocytes. The cytotoxicity and the effects of both peptides on MN and PMN morphology were determined with the Alamar‐Blue assay and scanning electron microscopy, respectively. The ability of Os and Os‐C to induce reactive oxygen species (ROS) and to protect against 2,2′‐azobis(2‐amidinopropane) dihydrochloride–induced oxidative damage in both cell populations was evaluated using 2′,7′‐dichlorofluorescin diacetate (DCFH‐DA). Using fluorescently labeled peptides, the ability of the peptides to cross the cell membranes of MN and PMN was also evaluated. At the minimum bactericidal concentrations of Os and Os‐C, neither peptide was cytotoxic. Os caused morphological features of toxicity at 100 μM, entered MN cells, and also protected these cells against oxidative damage. Os‐C caused MN and PMN leukocyte activation associated with ROS formation and was unable to penetrate cell membranes, indicating extracellular membrane interactions. This study confirms that both Os and Os‐C at less than 100 μM are not cytotoxic. The MN‐specific uptake of Os identifies it as a cell‐specific cargo‐carrier peptide, with additional anti‐inflammatory properties. In contrast, the ability of Os‐C to activate MN and PMN cells implies that this peptide should be further evaluated as an AMP, which, in addition to its ability to eradicate infection, can further enhance host immunity. These novel characteristics of Os and Os‐C indicate that these AMPs as peptides can be further developed for specific applications.

Research paper thumbnail of Investigation into the mechanism of action of the antimicrobial peptides Os and Os-C derived from a tick defensin

Peptides, 2015

Highlights • Os and Os-C caused altered intracellular morphology of E. coli and B. subtilis. • Me... more Highlights • Os and Os-C caused altered intracellular morphology of E. coli and B. subtilis. • Membrane effects were observed with fluorescence and TEM studies. • Os and Os-C were able to enter bacterial cells. • The peptides may have intracellular targets such as DNA. • Differences observed between Os and Os-C indicate dissimilar modes of action.

Research paper thumbnail of A descriptive study to provide evidence of the teratogenic and cellular effects of sibutramine and ephedrine on cardiac- and liver-tissue of chick embryos

Microscopy research and technique, Jan 3, 2015

Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influenc... more Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influence normal foetal development. Although the use of drugs during pregnancy should generally be avoided, exposure of the developing foetus to teratogens may occur unknowingly since these compounds may be hidden in products that are being marketed as "all natural." The aim of the current study was to investigate the possible teratogenic and cellular effects of sibutramine-a serotonin-norepinephrine reuptake inhibitor used in the treatment of obesity-on the heart and liver tissue of chick embryos. Ephedrine was used as a positive control. The chick embryo model was chosen because it has been used in studying developmental and experimental biology and teratology with great success. The embryos were exposed to three different concentrations of sibutramine and ephedrine respectively. The results obtained revealed that both compounds exhibited embryotoxicity when compared to the control ...

Research paper thumbnail of Anin ovoinvestigation into the hepatotoxicity of cadmium and chromium evaluated with light- and transmission electron microscopy and electron energy-loss spectroscopy

Journal of Environmental Science and Health, Part A, 2015

Excessive agriculture, transport and mining often lead to the contamination of valuable water res... more Excessive agriculture, transport and mining often lead to the contamination of valuable water resources. Communities using this water for drinking, washing, bathing and the irrigation of crops are continuously being exposed to these heavy metals. The most vulnerable is the developing fetus. Cadmium (Cd) and chrome (Cr) were identified as two of the most prevalent heavy metal water contaminants in South Africa. In this study, chicken embryos at the stage of early organogenesis were exposed to a single dosage of 0.430 mM physiological dosage (PD) and 430 mM(£1000 PD) CdCl 2 , as well as 0.476 mM (PD) and 746 mM(£1000 PD) K 2 Cr 2 O 7. At day 14, when all organ systems were completely developed, the embryos were terminated and the effect of these metals on liver tissue and cellular morphology was determined with light-and transmission electron microscopy (TEM). The intracellular localization of these metals was determined using electron energy-loss spectroscopy (EELS). With light microscopy, the PD of both Cd and Cr had no effect on liver tissue or cellular morphology. At £1000 PD both Cd and Cr caused sinusoid dilation and tissue necrosis. With TEM analysis, Cd exposed hepatocytes presented with irregular chromatin condensation, ruptured cellular membranes and damaged or absent organelles. In contrast Cr caused only slight mitochondrial damage. EELS revealed the bio-accumulation of Cd and Cr along the cristae of the mitochondria and chromatin of the nuclei.

Research paper thumbnail of An In Ovo Investigation of the Ultrastructural Effects of the Heavy Metals Cadmium and Chromium on Liver Tissue

Microscopy and Microanalysis, 2014

Many heavy metals are essential for human biological functions, but some heavy metals, especially... more Many heavy metals are essential for human biological functions, but some heavy metals, especially at high concentrations, can have toxic, carcinogenic and/or teratogenic effects in humans. South Africa is the world's largest reserve of minerals and due to extensive mining activity, air and water pollution occurs [1, 2]. Metal exposure occurs mostly through the ingestion of contaminated water; used for drinking, cooking and for agricultural purposes [3]. In this study the effect of heavy metals, cadmium (Cd) and chromium (Cr) were evaluated due to the high risk of exposure in South Africa. In recent studies, high levels of Cd and Cr were found in rivers and dams in several provinces in South Africa [4-6]. The most vulnerable population to be affected by heavy metal exposure is pregnant women with developing embryos and young children living in rural communities. In the human body, Cd and Cr are metabolized differently, but the consequences are similar namely oxidative stress that leads to DNA damage, apoptosis and lipid peroxidation [7-9]. Thus, the purpose of this study was to evaluate the ultrastructural effects of Cd and Cr on liver tissue by using the in ovo model. Analytical techniques energy dispersive spectroscopy (EDS) and electron energy-loss spectroscopy (EELS) were used to confirm the presence of these metals in liver tissue.

Research paper thumbnail of Premature Collagen Fibril Formation, Fibroblast-Mast Cell Interactions and Mast Cell-Mediated Phagocytosis of Collagen in Keloids

Ultrastructural Pathology, 2015

Keloids are benign hyper-proliferative growths of fibrous tissue, where increased fibroblast acti... more Keloids are benign hyper-proliferative growths of fibrous tissue, where increased fibroblast activity results in abnormal collagen deposition. Excessive inflammation is a characteristic feature of keloids but little is known about the underlying ultrastructural features of keloids related to collagen processing, fibril and fibre formation, the interaction between fibroblasts and associated collagen fibres and mast cells. In this study, the ultrastructure of the dermis of keloid patients was evaluated using light and transmission electron microscopy techniques. Abnormal intracellular premature collagen fibril formation was observed. Phagocytosis of collagen fibrils by mast cells was a common ultrastructural feature of keloid tissue as was a close or direct 2 association between fibroblasts and mast cells. Based on these findings and recent advances in knowledge related to collagen synthesis, fibril formation and processing we hypothesise that keloid formation is primary due to abnormal collagen synthesis where the consequent accumulation of collagen fibres causes increased mast cell recruitment and collagen phagocytosis. Subsequent release of mast cell derived mediators then promotes further collagen synthesis. The observation of early formation in keloid tissue of premature insoluble collagen fibrils supports previous studies that enzymes such as procollagen C-proteinase are important early therapeutic targets.

Research paper thumbnail of Feasibility of high pressure freezing with freeze substitution after long-term storage in chemical fixatives

Microscopy Research and Technique, 2013

Fixation of biological samples is an important process especially related to histo-logical and ul... more Fixation of biological samples is an important process especially related to histo-logical and ultrastructural studies. Chemical fixation was the primary method of fixing tissue for transmission electron microscopy for many years, as it provides adequate preservation of the morphology of cells and organelles. High pressure freezing (HPF) and freeze substitution (FS) is a newer alternative method that rapidly freezes non-cryoprotected samples that are then slowly heated in the FS medium, allowing penetration of the tissue to insure adequate fixation. This study addresses several issues related to tissue preservation for electron microscopy. Using mice liver tissue as model the difference between samples fixed chemically or with HPF immediately after excision, or stored before chemical or HPF fixation were tested with specific focus on the nuclear membrane. Findings are that immediate HPF is the method of choice compared to chemical fixation. Of the chemical fixatives, immediate fixation with 2.5% glutaraldehyde (GA)/form-aldehyde (FA) is the best in preserving membrane morphology, 2.5% GA can be used as alternative for stored and then chemically processed samples, with 10% formalin being suitable as a storage medium only if followed by HPF fixation. Overall, storage leads to lower ultrastructural preservation, but HPF with FS can minimize these artifacts relative to other processing protocols.

Research paper thumbnail of Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi

Journal of Peptide Science, 2013

Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a Signature __________________________... more Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a Signature __________________________________ Date 06/02/2014 © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a 2.4 Circular dichroism secondary structure determination 2.5 3-Dimentional structure construction 2.6 Antibacterial activity assays 2.6.1 Micro-dilution broth assay 2.6.2 Colony forming unit assay 2.6.3 Turbidity assays 2.7 SYTOX Green assay 2.7.1 Preliminary SYTOX green experiments 2.7.2 Optimising the bacterial concentration 2.7.3 Minimum bactericidal concentration determination of peptides in the presence of an increased bacterial concentration 2.7.4 Time study with SYTOX Green fluorescence 2.7.5 Effects of EDTA and Triton X-100 addition on SYTOX Green fluorescence of Gram-positive bacterial strains 2.8 Plasmid binding assay 2.9 Cytotoxicity 2.10 Data and statistical analysis Chapter 3: Results 3.1 Peptide characterisation 3.2 3-Dimentional structure modelling 3.3 Antibacterial activities of synthetic peptides 3.3.1 Determination of minimum inhibitory and minimum bactericidal concentrations 3.3.2 Determination minimum bactericidal concentrations by the CFU method 3.4 Effects of salt and serum on antibacterial activity © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a iii 3.5 Killing kinetics 3.6 Membrane permeabilisation studies 3.7 Plasmid binding properties of Os and Os-C 3.8 Cytotoxicity Chapter 4: Discussion Chapter 5: Conclusion and references © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a

Research paper thumbnail of A descriptive study to provide evidence of the teratogenic and cellular effects of sibutramine and ephedrine on cardiac- and liver-tissue of chick embryos

Microscopy research and technique, Jan 3, 2015

Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influenc... more Exposure to drugs during pregnancy is a major concern, as some teratogenic compounds can influence normal foetal development. Although the use of drugs during pregnancy should generally be avoided, exposure of the developing foetus to teratogens may occur unknowingly since these compounds may be hidden in products that are being marketed as "all natural." The aim of the current study was to investigate the possible teratogenic and cellular effects of sibutramine-a serotonin-norepinephrine reuptake inhibitor used in the treatment of obesity-on the heart and liver tissue of chick embryos. Ephedrine was used as a positive control. The chick embryo model was chosen because it has been used in studying developmental and experimental biology and teratology with great success. The embryos were exposed to three different concentrations of sibutramine and ephedrine respectively. The results obtained revealed that both compounds exhibited embryotoxicity when compared to the control ...

Research paper thumbnail of An in ovo investigation into the hepatotoxicity of cadmium and chromium evaluated with light- and transmission electron microscopy and electron energy-loss spectroscopy

Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering

Excessive agriculture, transport and mining often lead to the contamination of valuable water res... more Excessive agriculture, transport and mining often lead to the contamination of valuable water resources. Communities using this water for drinking, washing, bathing and the irrigation of crops are continuously being exposed to these heavy metals. The most vulnerable is the developing fetus. Cadmium (Cd) and chrome (Cr) were identified as two of the most prevalent heavy metal water contaminants in South Africa. In this study, chicken embryos at the stage of early organogenesis were exposed to a single dosage of 0.430 μM physiological dosage (PD) and 430 μM (×1000 PD) CdCl2, as well as 0.476 μM (PD) and 746 μM (×1000 PD) K2Cr2O7. At day 14, when all organ systems were completely developed, the embryos were terminated and the effect of these metals on liver tissue and cellular morphology was determined with light- and transmission electron microscopy (TEM). The intracellular localization of these metals was determined using electron energy-loss spectroscopy (EELS). With light microscop...

Research paper thumbnail of Premature Collagen Fibril Formation, Fibroblast-Mast Cell Interactions and Mast Cell-Mediated Phagocytosis of Collagen in Keloids

Ultrastructural Pathology, 2015

Abstract Keloids are benign hyper-proliferative growths of fibrous tissue where increased fibrobl... more Abstract Keloids are benign hyper-proliferative growths of fibrous tissue where increased fibroblast activity results in abnormal collagen deposition. Excessive inflammation is a characteristic feature of keloids, but little is known about the underlying ultrastructural features of keloids related to collagen processing, fibril and fiber formation, the interaction between fibroblasts and associated collagen fibers and mast cells. In this study, the ultrastructure of the dermis of keloid patients was evaluated using light and transmission electron microscopy techniques. Abnormal intracellular premature collagen fibril formation was observed. Phagocytosis of collagen fibrils by mast cells was a common ultrastructural feature of keloid tissue as was a close or direct association between fibroblasts and mast cells. Based on these findings and recent advances in knowledge related to collagen synthesis, fibril formation and processing, we hypothesize that keloid formation is primarily due to abnormal collagen synthesis where the consequent accumulation of collagen fibers causes increased mast cell recruitment and collagen phagocytosis. Subsequent release of mast cell-derived mediators then promotes further collagen synthesis. The observation of early formation in keloid tissue of premature insoluble collagen fibrils supports previous studies that enzymes such as procollagen C-proteinase are important early therapeutic targets.

Research paper thumbnail of Feasibility of high pressure freezing with freeze substitution after long-term storage in chemical fixatives

Microscopy Research and Technique, 2013

Fixation of biological samples is an important process especially related to histological and ult... more Fixation of biological samples is an important process especially related to histological and ultrastructural studies. Chemical fixation was the primary method of fixing tissue for transmission electron microscopy for many years, as it provides adequate preservation of the morphology of cells and organelles. High pressure freezing (HPF) and freeze substitution (FS) is a newer alternative method that rapidly freezes non-cryoprotected samples that are then slowly heated in the FS medium, allowing penetration of the tissue to insure adequate fixation. This study addresses several issues related to tissue preservation for electron microscopy. Using mice liver tissue as model the difference between samples fixed chemically or with HPF immediately after excision, or stored before chemical or HPF fixation were tested with specific focus on the nuclear membrane. Findings are that immediate HPF is the method of choice compared to chemical fixation. Of the chemical fixatives, immediate fixation with 2.5% glutaraldehyde (GA)/formaldehyde (FA) is the best in preserving membrane morphology, 2.5% GA can be used as alternative for stored and then chemically processed samples, with 10% formalin being suitable as a storage medium only if followed by HPF fixation. Overall, storage leads to lower ultrastructural preservation, but HPF with FS can minimize these artifacts relative to other processing protocols.

Research paper thumbnail of Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi

Journal of Peptide Science, 2013