Thesis (Ph. D.)--University of Chicago, 1934. / Vita. Lithoprinted. "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois."

Thesis (M.A.)--Kutztown State College. / Source: Masters Abstracts International, Volume: 45-06, page: 3170. Bibliography: leaves 60-61.

Commercial development of the fungicide prochloraz for the control of pre- and post-harvest diseases in fruit crops has been restricted by the occasional occurrence of 'musty' taints. The primary aims of this research were to identify the cause of taint and and its means of formation. Sensitive and selective residue methodology based upon determination by gas chromatography with mass selective detection was devised, validated and used to establish 2,4,6-trichloroanisole (2,4,6-TCA) as the direct cause of taint by analysis of field-treated samples and studies involving 14C-radiolabelled prochloraz. Evaluation of analytical results in conjunction with corresponding sensory data led to proposals of flavour threshold levels ranging between 0.04 and 1.0mug/kg for 2,4,6-TCA in different fruit types. Formation of the anisole in pre-harvest treatment situations was shown to proceed via the minor plant metabolite 2,4,6-trichlorophenol (2,4,6-TCP) as the direct precursor; under post-harvest conditions, however, metabolism of prochloraz was minimal, and 2,4,6-TCA taints arose primarily from 2,4,6-TCP as an impurity (measured at 0.9% w/w) in the commercial emulsifiable concentrate formulation. Detailed investigation of the relationship between 2,4,6-TCP and 2,4,6-TCA under controlled conditions demonstrated that certain fruit types possess a capacity for direct O-methylation of the phenol to the anisole, whereas others do not. These findings were generally consistent with occurrences of taints associated with prochloraz. Kinetic studies of the active O-methyltransferase system in apple homogenates indicated the same Vmax value for 2-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol and 2,4,6-TCP. Reactivity in this series was found to be closely related to the ability of the molecules to to form effective nucleophiles for reaction with s-adenosylmethionine as the assumed methyl donor, and a linear relationship was established between chlorophenol pKa and log(apparent Km). The O-methylation of 2,4,6-TCP, whilst inhibited competitively by other o-chlorophenolic substrates, remained unaffected by the addition of representative plant o-diphenolics previously reported as substrates for O-methylation in plants.

Campylobacterjejuni, a Gram-negative enteric pathogen, is the leading cause of bacterial gastroenteritis in the developed world. A C. jejuni strain 8 1-176 transposon library was used to screen for mutants over-producing a calcofluor white (CFW)-reactive polymer implicated in biofilm formation. This identified two lipooligosaccharide (LOS) core mutants: one defective for a two-domain glycosyltransferase (lgtF), and the other defective in a heptosyltransferase (waaF). To determine if other LOS core mutants displayed a similar phenotype, and to explore other biological outcomes of step-wise LOS truncations on C. jejuni stress resistance and pathogenesis, mutant strains defective for GaiT and CstII were also constructed. Silver stain and mass spectrometry analyses confirmed the sequential truncation of sialic acid (ΔcstII), galactose (ΔgalT), two glucoses (ΔlgtF), and heptose II (ΔwaaF). While the ΔlgtF and ΔwaaF mutants exhibited enhanced biofilm formation and ΔlgtF displayed increased sensitivity to complement killing, no effect for these phenotypes and only modest alterations in CFW reactivity were seen with partial outer core truncations. Deletion of LgtF had no effect on mouse colonization in vivo, or on invasion and intracellular survival in epithelial cells in vitro. In contrast, the ΔwaaF mutant exhibited a significant defect in intracellular survival in vitro. Interestingly, the mutants exhibited stepwise increases in susceptibility to the antimicrobial peptide LL-37, with /waaF and ΔlgtF being more susceptible and ΔgalT and ΔstII being more resistant than wild type. In contrast, all of the mutants were highly susceptible to polymyxin B. This is the first report of C. jejuni susceptibility to LL-37 and of LOS affecting polymyxin B resistance. Each of these appears to be independent of overt effects on outer membrane protein expression, membrane stability, or surface hydrophobicity. Together, our data indicate that the length and specific moieties of the LOS play important roles in C. jejuni biology, and suggest a dynamic interplay of the LOS with other stress resistance factors. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

"Of considerable interest among mathematicians is the problem of the determination of primality of positive integers. For a small integer, N, we may say that N is prime or composite merely by trying to divide N by all primes less than or equal to the square root of N since if N is composite, one of its factors must be [less than or equal to] the square root of N. However, if N is large this test loses its practicality and we must resort to a more feasible method. It is the purpose of this paper to trace and show the development of such methods"--Introduction. / "June, 1959." / Typescript. / "Submitted to the Graduate Council of Florida State University in partial fulfillment of the requirements for the degree of Master of Science." / Advisor: Paul J. McCarthy, Professor Directing Paper. / Includes bibliographical references (leaf 28).

Here, we present a study of polar residues within the membrane core of alpha-helical membrane proteins. As expected, polar residues are less frequent in the membrane than expected. Further, most of these residues are buried within the interior of the protein and are only rarely exposed to lipids. However, the polar groups often border internal water filled cavities, even if the rest of the sidechain is buried. A survey of their functional roles in known structures showed that the polar residues are often directly involved in binding of small compounds, especially in channels and transporters, but other functions including proton transfer, catalysis, and selectivity have also been attributed to these proteins. Among the polar residues histidines often interact with prosthetic groups in photosynthetic-and oxidoreductase-related proteins, whereas pro-lines often are required for conformational changes of the proteins. Indeed, the polar residues in the membrane core are more conserved than other residues in the core, as well as more conserved than polar residues outside the membrane. The reason is twofold; they are often (i) buried in the interior of the protein and (ii) directly involved in the function of the proteins. Finally, a method to identify which polar residues are present within the membrane core directly from protein sequences was developed. Applying the method to the set of all human membrane proteins the prediction indicates that polar residues were most frequent among active transporter proteins and GPCRs, whereas infrequent in families with few transmembrane regions, such as non-GPCR receptors. Proteins 2011; 79: 79-91. / <p>authorCount :3</p>

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 107-118). Also available in electronic version.

Yes

Thesis (M. Tech. ) - Central University of Technology, Free State, 2006 / Antibiotics have been used on animals since the Second World War for therapeutic purposes. The risks associated with the use of antibiotics in food animals are enormous, due to the possibility of resistance of organisms caused by the usage of low levels of antibiotics. The goals of this study were to determine the prevalence of antibiotic residues in C grade milk cows, and to determine the practices and knowledge of producers regarding the use of antibiotics as well as the knowledge and habits of consumers. In the study the presence of antibiotic residues was tested by means of microbiological inhibition testing. Fifteen percent of all tested samples tested positive for the presence of antibiotic residues. Eleven samples that tested positive on the microbiological inhibition test were sent to the Onderstepoort Veterinary Institute for confirmation. The knowledge of the consumer as well as that of the producer was tested by means of a questionnaire and then processed statistically. Producers were, in general, fairly ignorant regarding the withdrawal period of antibiotic residues. Age and the combination of age and reproduction were the common reasons for the selling of milk cows. Both the sampling and the questionnaires proved that the presence of antibiotic residues is higher than that stated in literature. The selling of the animals was mostly by auction or directly to the abattoirs. Consumer practices regarding the antibiotic residues were mostly in order, although consumers did not have knowledge regarding antibiotic residues. High temperatures, for example in the frying or grilling of meat, will reduce the presence of antibiotic residues because these effects have an influence on the presence of antibiotic residues (Rose et al., 1995). Almost 75% of consumers describe antibiotics in a positive manner. Milk and meat are regarded as posing the greatest risk for the origin of antibiotic residues. A lack of general knowledge regarding antibiotic residues was noteworthy, especially from the consumers of Thaba ’Nchu and Heidedal. The wrong usage of antibiotics by medical practitioners and consumers will certainly have consequences. Most of the consumers (112/227 respondents) indicated that they always completed a course of antibiotics. Forty-nine respondents indicated that they had already used antibiotics and that the therapy was unsuccessful. Antibiotic residues are still present so the risk to the consumer is still viable. Improved sampling and monitoring at abattoirs both for local and export abattoirs is necessary. The “farm to fork” concept and financial incentives by way of subsidies for residue-free products is a positive step. South African consumers are not quality conscious and further studies are necessary to improve the quality and safety of meat.

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