Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. Includes 2 studies: The solubility and complexing properties of oxytetracycline and tetracycline : I. Interactions in aqueous solution / By Takeru Higuchi and Eugene H. Gans -- The solubility and complexing properties of oxytetracycline and tetracycline : II. Interactions in non-aqueous solution / By Takeru Higuchi and Eugene H. Gans. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 114-121).

Walleye fry stocking is common practice but success is rarely monitored. Use of oxytetracycline (OTC) can be used as a marking tool to identify stocked fish from naturally produced fish and determine stocking success. Through a series of experiments, parameters in the marking methodology were assessed for their effect on mark quality and retention of the mark over time. Mark quality was improved by marking fry at three days post hatch. Water source also significantly affected OTC mark quality. The use of powdered OTC produced higher quality marks than the use of liquid OTC. Retention of OTC marks was related to the quality of the OTC mark. Electrofishing surveys conducted on five lakes found high recruitment (>80%) among stocked walleye on two lakes, with more 40% recruitment on a third lake. This study found that stocked walleye fry were successfully recruited into the age 0+ year class. / October 2015

Thesis (MMedVet (Pharm) (Veterinary Pharmacology, Veterinary Science))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

Desde su descubrimiento, los antibióticos han marcado un hito importante en el tratamiento de enfermedades y han permitido la realización de intervenciones quirúrgicas antes consideradas como letales. Sin embargo, el uso excesivo de antibióticos puede alterar la microbiota, causando disbiosis y aumentando la predisposición al desarrollo de diversas patologías a largo plazo. Antibióticos de amplio espectro como la Oxitetraciclina (OTC) se utilizan de manera desmesurada en diversas industrias agroalimentarias. La relación entre el mecanismo de acción de OTC y alteraciones de la microbiota es aún desconocida. Actualmente, se conoce que OTC funciona como inhibidor de la síntesis de proteínas durante la fase de elongación. Dicho fase de la síntesis de proteínas es altamente conservada entre las bacterias y no explicaría el efecto diferenciado entre géneros bacterianos asociados a disbiosis. Al unirse a la subunidad menor 30S del ribosoma, existe la posibilidad de que OTC también actúe en otras fases de la síntesis proteica. Entre ellas destaca la iniciación de la traducción del ARNm al presentar al menos dos mecanismos alternativos, utilizados diversamente entre las bacterias. El primero utiliza los factores de iniciación IF1, IF2 e IF3, mientras que el segundo utiliza principalmente IF1 e IF2. En el presente estudio se evalúa a OTC como posible inhibidor de la iniciación de la síntesis de proteínas dependiente de los tres factores mediante métodos bioquímicos y análisis informático de modelamiento estructural. Los resultados indican que IF1 es susceptible a OTC, probablemente por su posicionamiento cercano al antibiótico en el ribosoma. Como consecuencia, OTC induce una mayor estabilización de IF1 en el ribosoma, que va en aumento a través de los complejos intermediarios de iniciación, alcanzando un incremento del 40%. La estabilización de IF1, reducción de su capacidad de disociación del ribosoma, conllevaría a una inhibición de la formación del complejo de iniciación 70S. Los resultados aquí expuestos sugieren un nuevo mecanismo de acción de OTC durante la iniciación de la síntesis de proteínas. El entendimiento del nuevo mecanismo de acción de OTC contribuye con una explicación novedosa y base para el entendimiento de disbiosis mediada por el fármaco. Además, los resultados proporcionan las bases de futuras investigaciones para el desarrollo de nuevos antibióticos que actúen en el mismo blanco molecular. / Antibiotics have stablished an important milestone since their discovery, allowing the treatment of infectious diseases and surgical procedures otherwise considered lethal. However, recent studies show that the use of antibiotics can alter the microbiota, causing dysbiosis and leading to the development of diverse pathologies. In particular, broad- spectrum antibiotics such as Oxytetracycline (OTC) are widely used in agricultural and food industries. The relationship between the molecular mechanism of OTC and microbiota modifications is still unknown. The current model suggests that OTC inhibits the elongation phase of protein synthesis inhibitor. This phase of protein synthesis is highly conserved among bacteria and cannot explain the differentiated effect of OTC among bacterial genus. OTC could act in other phases of protein synthesis since the drug binds to 30S small ribosomal subunit. Among these, mRNA translation initiation stands out since it is represented by at least two alternative mechanisms in bacteria. The first mechanism uses initiation factors IF1, IF2 and IF3, while the second uses mainly IF1 and IF2. In the present study, OTC has been evaluated as a potential protein synthesis inhibitor acting at initiation of translation. Particularly, the study focuses in the mechanism that uses all three initiation factors employing biochemical methods and computer analysis of structural modelling. The results indicate that IF1 is susceptible to OTC, probably due to the near positioning with respect to the antibiotic in the ribosome. Consequently, OTC increases the stabilization of IF1 in the ribosome up to 40% along all intermediate initiation complexes. IF1 stabilization would inhibit of 70S initiation complex formation, suggesting a new mechanism of action for OTC during translation initiation. This finding would explain how OTC causes dysbiosis and provides further basis for future research of new antibiotics with a similar molecular mechanism. / Tesis

Bacterial polyketides possess an enormous range of chemical diversity and biological function. Many polyketides such as tetracycline, epothilone, and rapamycin have been developed into key clinical pharmaceuticals in a broad range of therapeutic areas. Sequencing of bacterial genomes has shown that there are many more polyketide biosynthetic pathways than there are polyketides isolated from standard cultivation techniques. These genetically encoded polyketide natural products from cultivatable and uncultivatable bacteria represent one of the greatest remaining untapped reservoirs of new natural product diversity. To access this untapped diversity of polyketide products, a general method for heterologous expression of these pathways is needed. Heterologous expression has proven to be a valuable asset in the discovery, production, engineering, and characterization of bacterial secondary metabolites and the complex enzymology involved in their biosynthesis. Herein we discuss the development and investigation of two unique heterologous expression platforms utilizing host strains of Myxococcus xanthus and Escherichia coli. Using our developed heterologous hosts, we were able to produce the Streptomyces rimosus polyketide oxytetracycline. Through production of oxytetracycline in E .coli we have identified the potential of alternative transcription factors as regulators of secondary metabolism. Further investigation and development of alternative transcription factors as regulators of secondary metabolism in heterologous hosts could benefit the development of robust general methodology for the heterologous expression of polyketides.

Bacterial polyketides possess an enormous range of chemical diversity and biological function. Many polyketides such as tetracycline, epothilone, and rapamycin have been developed into key clinical pharmaceuticals in a broad range of therapeutic areas. Sequencing of bacterial genomes has shown that there are many more polyketide biosynthetic pathways than there are polyketides isolated from standard cultivation techniques. These genetically encoded polyketide natural products from cultivatable and uncultivatable bacteria represent one of the greatest remaining untapped reservoirs of new natural product diversity. To access this untapped diversity of polyketide products, a general method for heterologous expression of these pathways is needed. Heterologous expression has proven to be a valuable asset in the discovery, production, engineering, and characterization of bacterial secondary metabolites and the complex enzymology involved in their biosynthesis. Herein we discuss the development and investigation of two unique heterologous expression platforms utilizing host strains of Myxococcus xanthus and Escherichia coli. Using our developed heterologous hosts, we were able to produce the Streptomyces rimosus polyketide oxytetracycline. Through production of oxytetracycline in E .coli we have identified the potential of alternative transcription factors as regulators of secondary metabolism. Further investigation and development of alternative transcription factors as regulators of secondary metabolism in heterologous hosts could benefit the development of robust general methodology for the heterologous expression of polyketides.

Bacterial polyketides possess an enormous range of chemical diversity and biological function. Many polyketides such as tetracycline, epothilone, and rapamycin have been developed into key clinical pharmaceuticals in a broad range of therapeutic areas. Sequencing of bacterial genomes has shown that there are many more polyketide biosynthetic pathways than there are polyketides isolated from standard cultivation techniques. These genetically encoded polyketide natural products from cultivatable and uncultivatable bacteria represent one of the greatest remaining untapped reservoirs of new natural product diversity. To access this untapped diversity of polyketide products, a general method for heterologous expression of these pathways is needed. Heterologous expression has proven to be a valuable asset in the discovery, production, engineering, and characterization of bacterial secondary metabolites and the complex enzymology involved in their biosynthesis. Herein we discuss the development and investigation of two unique heterologous expression platforms utilizing host strains of Myxococcus xanthus and Escherichia coli. Using our developed heterologous hosts, we were able to produce the Streptomyces rimosus polyketide oxytetracycline. Through production of oxytetracycline in E .coli we have identified the potential of alternative transcription factors as regulators of secondary metabolism. Further investigation and development of alternative transcription factors as regulators of secondary metabolism in heterologous hosts could benefit the development of robust general methodology for the heterologous expression of polyketides.

Oxytetracycline (OTC) is a broad spectrum antibiotic used extensively in the agricultural and human-health sector, and is effective against various gram positive and –negative bacteria as well as large viruses and certain pathogenic Rickettsiae. This study addresses the lack of voltammetric knowledge regarding the electroanalytical characterisation of OTC and its analysis in complex matrices. Cyclic voltammetry (CV) revealed several irreversible anodic peaks for OTC at a bare glassy carbon electrode (GCE). These current responses were improved through the selection of a diluent for OTC stock preparation, electrolyte solution and electrolyte pH, stir time and applied preconditioning potential. Under enhanced adsorptive conditions and using square wave voltammetry (SWV), a detection limit of 24.3 nM was achieved. The electrode surface could be renewed in vitro for 10 successive scans. OTC oxidation was characterised as a one electron:one proton ECiE mechanisms. Next, investigating the viability of voltammetry in various complex microbiological growth media revealed that selected growth media contained interfering redox active components, which, while simultaneously coating the electrode surface, effectively reduced GCE performance and lowered the active electrode surface area, as ascertained through CV and electrochemical impedance spectroscopy (EIS) studies. This interference lowered OTC current response in the presence of growth media which was partially recovered by appropriate growth media selection and sample dilution. In testing the use of acid functionalised multi-walled carbon nanotubes (MWCNTs) to improve anodic OTC response, charge-based attraction was observed between the MWCNT dispersal agent Nafion® and OTC, while increased surface area associated with prolonged acid functionalisation time aided in improving OTC current response.