Together with the advancements in animal cloning, the ability to efficiently target specific genes in somatic cells would greatly enhance several areas of research. While it has been possible for quite some time to target specific genes in the germ cells of mice, the advancements in somatic cell gene targeting has been slowed for two main reasons. First, the finite lifespan of somatic cells, due mainly to the inability of the somatic cells to regenerate or maintain their telomeres, poses a major problem given the lengthy selection process needed to identify a targeting event. The second problem is the overall inefficiency of homologous recombination. A double strand break or introduction of foreign DNA into a cell can be processed either through the homologous recombination or non-homologous end joining pathways. Of these two, non-homologous end joining is dominant in somatic cells. A two plasmid recombination system was used to study the effects of the manipulation of several non-homologous end joining and homologous recombination pathway molecules on the rates of homologous recombination in porcine fetal fibroblasts. In addition, the effect of telomerase expression, cell synchrony, and DNA nuclear delivery was examined. Results indicate a strong positive relationship between inactivation of p53, cell synchronization, and efficient DNA nuclear delivery in enhancing the rate of homologous recombination. These findings were then applied to an actual locus in the pig, the α1,3 galactosyltransferase gene. Results from these transfections are compared to published accounts of successful targeting at this locus and possibilities for the differences found are discussed.

The skin, by weight, is the largest organ of the body. Human skin serves to provide several important functions that may be classified. in a general context, as protective, maintaining homeostasis and sensing. The outermost layer of the skin, the stratum corneum, has an essential role as a barrier against the transport of water and of chemical and biological agents. In this study acyclovir (ACV), an antiviral used for treating the varicella zoster virus, was used. It is sensible to say that a hydrophilic drug like acyclovir needs a delivery vehicle or penetration enhancer to permeate the skin with more ease. In an attempt to enhance the permeation of acyclovir, it was formulated in a delivery vehicle with the same formulation as for a micro-emulsion. Increasing percentages of the surfactant, Brij 97, were incorporated in the formulation to determine which of the four formulations is indeed a micro-emulsion. A gelating agent. carrageenan, was used to make the emulsion transdermally more applicable; the influence of this component on the transdermal delivery of acyclovir was also determined. Therefore the aim of this study was to determine: -The effect of a drug delivery vehicle on the transdermal delivery of acyclovir; -The specific formulation of a micro-emulsion and -The influence of a gelating agent on the transdermal delivery of acyclovir. Diffusion studies were performed in vertically mounted glass Franz diffusion cells. The epidermis of female abdominal skin, obtained after abdomeoplasty, was heat separated from the dermis. One millilitre of emulsion (0.1%: 1mg/ml ACV) was added to the skin sample in the donor side of the diffusion cell. The control solution had an equivalent amount of active in water and was added to the donor compartment in a separate experiment. The receptor phase was PBS (phosphate buffered solution). The entire receptor phase of the cells was removed every second hour and was replaced with fresh receptor phase at 37°C. The amount of acyclovir in the receptor phase was determined by HPLC analysis. The cumulative amounts of the active that permeated the skin over the 24 hour period were plotted with the slope of the graphs representing the flux in ng/cm²/h. The average flux values of the experimental cells and control cells were compared. Results of the diffusion studies without carrageenan showed that increasing the concentration of the surfactant increased the diffusion of acyclovir. Permeation studies with carrageenan had a totally different outcome. The enhancement ratio of the experimental cells was much lower than that of the control cells. However the experimental cells showed a small increase as the concentration of the surfactant increased. From VanKel dissolution studies it could be seen that release of acyclovir from the emulsion was not a problem and that the active was available for absorption. Confocal studies were done to determine whether there were any vesicles in the emulsions. Vesicles were expected in the 25% Brij 97 emulsion because it was the same formulation as a micro-emulsion, but vesicles could only be found in the 4% and 8% Brij 97 emulsion. A previous study with acyclovir and three different delivery vehicles gave enhancement ratios between 0.32 to 2.92. Values obtained in this study of the 4% and 8% Brij 97 emulsion without carrageenan were more or less the same but the 15% and 25% Brij 97 emulsion had a much higher enhancement ratio. For the emulsions with carrageenan not one exceeded an enhancement ratio of 0.57. More studies still have to be done on micro-emulsions to determine which specific concentration of surfactant forms a micro-emulsion. The active itself and its physicochemical properties also play an important role in the diffusion studies with the specific delivery vehicle and further research has to be done with different model drugs. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2006.

No description available.

The skin, by weight, is the largest organ of the body. Human skin serves to provide several important functions that may be classified. in a general context, as protective, maintaining homeostasis and sensing. The outermost layer of the skin, the stratum corneum, has an essential role as a barrier against the transport of water and of chemical and biological agents. In this study acyclovir (ACV), an antiviral used for treating the varicella zoster virus, was used. It is sensible to say that a hydrophilic drug like acyclovir needs a delivery vehicle or penetration enhancer to permeate the skin with more ease. In an attempt to enhance the permeation of acyclovir, it was formulated in a delivery vehicle with the same formulation as for a micro-emulsion. Increasing percentages of the surfactant, Brij 97, were incorporated in the formulation to determine which of the four formulations is indeed a micro-emulsion. A gelating agent. carrageenan, was used to make the emulsion transdermally more applicable; the influence of this component on the transdermal delivery of acyclovir was also determined. Therefore the aim of this study was to determine: -The effect of a drug delivery vehicle on the transdermal delivery of acyclovir; -The specific formulation of a micro-emulsion and -The influence of a gelating agent on the transdermal delivery of acyclovir. Diffusion studies were performed in vertically mounted glass Franz diffusion cells. The epidermis of female abdominal skin, obtained after abdomeoplasty, was heat separated from the dermis. One millilitre of emulsion (0.1%: 1mg/ml ACV) was added to the skin sample in the donor side of the diffusion cell. The control solution had an equivalent amount of active in water and was added to the donor compartment in a separate experiment. The receptor phase was PBS (phosphate buffered solution). The entire receptor phase of the cells was removed every second hour and was replaced with fresh receptor phase at 37°C. The amount of acyclovir in the receptor phase was determined by HPLC analysis. The cumulative amounts of the active that permeated the skin over the 24 hour period were plotted with the slope of the graphs representing the flux in ng/cm²/h. The average flux values of the experimental cells and control cells were compared. Results of the diffusion studies without carrageenan showed that increasing the concentration of the surfactant increased the diffusion of acyclovir. Permeation studies with carrageenan had a totally different outcome. The enhancement ratio of the experimental cells was much lower than that of the control cells. However the experimental cells showed a small increase as the concentration of the surfactant increased. From VanKel dissolution studies it could be seen that release of acyclovir from the emulsion was not a problem and that the active was available for absorption. Confocal studies were done to determine whether there were any vesicles in the emulsions. Vesicles were expected in the 25% Brij 97 emulsion because it was the same formulation as a micro-emulsion, but vesicles could only be found in the 4% and 8% Brij 97 emulsion. A previous study with acyclovir and three different delivery vehicles gave enhancement ratios between 0.32 to 2.92. Values obtained in this study of the 4% and 8% Brij 97 emulsion without carrageenan were more or less the same but the 15% and 25% Brij 97 emulsion had a much higher enhancement ratio. For the emulsions with carrageenan not one exceeded an enhancement ratio of 0.57. More studies still have to be done on micro-emulsions to determine which specific concentration of surfactant forms a micro-emulsion. The active itself and its physicochemical properties also play an important role in the diffusion studies with the specific delivery vehicle and further research has to be done with different model drugs. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2006.

Development of the vertebrate central nervous system is a complex process that relies on the accurate spatiotemporal distribution of signaling centers during embryogenesis. These signals provide cells with positional information, which is integrated via transcription factors and gene regulatory elements to generate a specific downstream gene expression profile that confers specific cellular functions. It is of interest to determine how cells acquire their unique spatiotemporal gene expression patterns. The wide variety of expression profiles established along the dorsoventral axis of the neural tube provides a great system to address this question. Recent advances in zebrafish transgenic technology, along with the phenomenon of a fish-specific genome duplication event, have been exploited here to provide an efficient way of identifying and characterizing gene regulatory elements. An identified neuronal-specific enhancer near the ladybird locus has been incorporated into a transgenic zebrafish strain driving fluorescent reporter protein expression in a subset of dorsal interneurons / Molecular Biology and Genetics

Adenosine and adenosine analogues are recognised as cardioprotective agents due to the responses that they induce through the activation of myocardial adenosine receptors. Antioxidants such as nitroxide radicals have also been found to possess cardioprotective properties in biological systems, namely through their ability to scavenge the oxygen-based free radicals that are potentially damaging to tissues and cells. It was envisaged that the linking of an antioxidant moiety to adenosine would produce an adenosine analogue that activates adenosine receptors and also scavenges oxygen-derived free radicals in the body. Consequently, one aim of this project was to synthesise a series of adenosine analogues that possessed a nitroxide or a phenolic antioxidant at the N6 position of the adenosine skeleton. Allosteric ligands have several advantages over orthosteric ligands as potential therapeutic agents, and research into the allosteric enhancement of adenosine receptors is a burgeoning field. It was envisaged that the linking of an antioxidant moiety to an allosteric enhancer would produce a compound that enhances the response of endogenous activation of adenosine receptors and also scavenges oxygen-based free radicals in the body. Consequently, a second aim of this project was to synthesise a series of allosteric enhancers of the A1 adenosine receptor that possessed antioxidant capability endowed by a nitroxide or a phenolic antioxidant functionality. This project has resulted in the synthesis and characterisation of 19 novel N6 substituted adenosine analogues, and additionally 12 novel derivatised thiophenes. Each of the target compounds was tested for its ability to bind to each of the adenosine receptor subtypes and some analogues were found to be potent and selective adenosine receptor agonists.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [137]-139).