Thesis (M.S.) in Ecology and Environmental Science--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 74-77).

Thesis (M.S.)--University of Florida, 2003. / Title from title page of source document. Includes vita. Includes bibliographical references.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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The floral and pollination biology of jujubes (Ziziphus mauritiana) and longans (Dimocarpus longan) were studied near Hanoi, Vietnam. Jujube is a protandrous species with three phases of flowering. After a brief asexual phase, anthers dehisce and release pollen in the afternoon of the day of anthesis. Stigmas become most receptive the following day when flowers are actively secreting nectar. Both jujube and longan flowers are visited during the day by insects of many families, particularly honeybees and flies (syrphids, calliphorids, and muscids). Honeybees, Apis cerana, made up 84% of floral visitors to jujube flowers and 47 – 95% to longan inflorescences. Bagging experiments revealed that diurnal insect visitors are very important in fruit production of both jujubes and longans. In jujubes, no fruits were set during the first pollination trial early in the flowering period. Fruit set increased to 0.17% midway through flowering and 2.21% for the trial conducted late in the flowering period. Fruit set recorded one week after anthesis suggested that all types of pollination may result in fruits, but 7 weeks after anthesis only open pollination (unbagged flowers) and diurnal pollination treatments yielded fruits. Most fruits (~97%) were estimated to result from honeybee visits to flowers. Longans are also predominantly pollinated by diurnal insects (~84%), but with minor contributions from wind pollination (8.4%) and self-pollination (7.7%). A. cerana was estimated to contribute 67% of longan pollination. Pollination requirements for 39 Vietnamese crops were reviewed. Most benefit from insect pollination. For 8 crops important in Vietnamese agriculture for which there were sufficient data, crop yields and values were estimated. Honeybee pollination resulted in ~50% of yields of these 8 crops, contributing ~900 millionion USD of their total values. This analysis indicates that the pollination service provided by honeybees is enormous. / Association of Universities and Colleges of Canada (AUCC) and Canadian International Development Agency (CIDA): Tier 2 CIDA-UPCD Project.

Sterols serve two important biological functions in animals - they act as cellular membrane components, and as the precursor to steroid hormones. Insects require a dietary source of sterol because they cannot synthesize sterols de novo. Cholesterol is the most common sterol in plant-feeding insects, but because plants contain very little cholesterol, plant-feeding insects must convert plant sterols into cholesterol. In this dissertation I investigate the effect of common and novel plant sterols and steroids found in a transgenic tobacco line on several caterpillar species. I also explore the metabolism of these sterols and steroids, and use a microarray approach to identify genes involved in sterol use and metabolism in plant-feeding insects. I also study cholesterol homeostasis using a grasshopper species. Modified tobacco plants containing a novel sterol profile negatively affected performance three different caterpillar species, especially in the second generation. Insects reared on modified plants contained less total sterols and cholesterol than those on control plants having normal sterol profile. Similar results were found using artificial diets containing atypical steroids, e.g., cholestanol and cholestan-3-one, identified in the tobacco plants that were fed to my experimental caterpillars. More importantly, the sterol/steroid ratio, but not their absolute amount in the diets, determined the negative effects. Caterpillar species could convert stigmasterol, a common plant sterol, into cholesterol. They could also convert cholestan-3-one into cholestanol and epicholestanol, although this ability varied among different species. A microarray study, that focused on gene expression in midgut tissue, indicated that stigmasterol, cholestanol and cholestan-3-one could induce different gene expression level, and that cholestan-3-one caused a the largest pool of genes to be regulated. The genes possibly involved in the metabolism of stigmasterol and cholestan-3-one were reported. These findings are important in directing further research on the potential application of plant sterol modification to control pests in agricultural systems. Insect herbivores could behaviorally regulate the intake of several nutrients, but they could not regulate their sterol intake. They did, however, practice cholesterol homeostasis, by postingestively regulating tissue sterol levels, even when feeding on diets with high cholesterol content. Collectively, the results from this dissertation provide unique insight into cholesterol regulation, which is difficult to achieve in mammals that are capable of synthesizing their own sterols.

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Insect repellent N,N-diethyl-m-toluamide (DEET) and sunscreen oxybenzone are commonly incorporated into commercially available consumer care products that are utilized to prevent vector-borne diseases and skin aging and damage. Semisolid emulsion-based formulation has been extensively selected for active repellent and sunscreen ingredients due to their excellent solubilizing properties for both lipophilic and hydrophilic components and satisfactory customer acceptance. Under the ideal use situation, an appropriate and elegant emulsion-based formulation can minimize transdermal absorption of DEET and oxybenzone and maximize their skin protection effect. The percutaneous penetration profiles of DEET and oxybenzone from several emulsion-based formulations were evaluated and compared by using the in vitro diffusion experiments in this thesis. Various parameters in the emulsion formulations, such as emulsion type, emulsifier, emollient, penetration enhancer, thickening agent, and thixotropic properties of the emulsions, could exert significant influence on percutaneous permeation of the active ingredients from the preparations. An emulsion-based preparation using the emulsifier, Emulium 22, possessed the relatively lower skin permeation of DEET and oxybenzone than other emulsion-based preparations; it was selected for the in vivo animal study. This emulsion-based formulation containing DEET and/or oxybenzone was topically applied to rats once daily for a 60-day period to investigate systemic concentration and tissue deposition of DEET, oxybenzone, and their respective metabolites. This formulation produced lower systemic absorption of DEET and oxybenzone than the commercially available products reported in a previous animal study. The concurrent application of DEET and oxybenzone in this study did not show synergistic enhancement between the two compounds in plasma. The percutaneous penetration profiles of DEET and oxybenzone from different semisolid emulsions in the in vitro diffusion experiment provided the important information in selecting the appropriate formulation of DEET and oxybenzone for topical application. The in vivo animal study identified pharmacokinetics and biodistribution characteristics of DEET and oxybenzone from the promising lab-developed emulsion. Studies are ongoing to further improve formulation characteristics so that this emulsion-based preparation could be used to minimize overall transdermal permeation of DEET and oxybenzone from topical skin application.