Thesis (M.S.)--Villanova University, 2006. / Biology Dept. Includes bibliographical references.

There is an increasing body of evidence that conjugated linoleic acid (c9t11 CLA) suppresses chemically induced tumor development in cell cultures and animal models. Ruminant-derived foods make a major contribution to total fat consumption and are the main source of c9t11 CLA in the human diet. In light of the potential benefits to long-term human health, there has been increased interest in enhancing the concentrations of potentially beneficial fatty acids (FA) in milk and meat. Factors affecting c9t11CLA production and secretion into milk fat have been extensively studied the last 10 years and a large pool of knowledge has accumulated. However, little information is currently available about the effects of feeding c9t11 CLA- stimulating diets on rumen microbial ecology, particularly, bacterial species believed to be involved in the biohydrogenation (BH) process. The main objective of this study was to evaluate the effect of lipid source on the DNA concentrations of selected ruminal bacteria. Four continuous culture fermenters were used in 4 x 4 Latin square design with four periods of 10 d each. Treatment diets were fed (45 g/d DM basis) in three equal portions during the day. The diets were 1) control diet (50% alfalfa pellets, 50% concentrate, CON), 2) CON plus saturated fat (rumofat; SAT), 3) CON plus soybean oil (SBO), and 4) CON plus fish oil (FO). Lipid supplements were added at 3% of diet DM. Lipid supplements had no effect on feed digestibility, total VFA and acetate concentrations or fermenter pH. Propionate concentration was higher with the FO diet in comparison with the other treatment diets. Butyrate concentration was similar between the SBO and FO diets and both were lower than the levels for the CON and SAT diets. The concentration of VA in effluents increased with SBO and FO diets and was highest with SBO diet. The concentrations of C18:0 in effluents were lowest for the FO diet compared with the other treatment diets. The concentrations of c9t11 CLA in effluents were similar between SBO and FO diets and both were higher than levels for the CON and SAT diets. Concentrations of DNA for total bacteria, A. lipolytica, C. proteoclasticum and S. dextrinosolvens were similar for all diets. The concentrations of B. fibrisolvens (69.1 pg/45ng total DNA) and R. albus (1.96 pg/45ng total DNA) were least with the FO diet but were similar among the other treatment diets (SAT-104.2; 5.4, SBO-121.2; 5.71, and CON-126.3; 5.17 pg/45ng total DNA). S. ruminantium DNA concentration was highest with the FO diet and was least with the SAT diet (177.5, 54.9, 75.5, and 691.1 pg/20ng total DNA for treatment diets 1 to 4, respectively). In conclusion, SBO had no effect on bacterial DNA concentrations tested in this study and the inhibitory effects of FO on BH may be due in part to its influence on B. fibrisolvens, R. albus and S. ruminantium.

Lipid analyses of the leaves of Empetrum nigrum subspp. hermaphroditum with an upland distribution in the U.K. and the lowland E. nigrum subspp. nigrum revealed a) that the lowland subspecies had higher total and neutral lipid levels throughout 1979 b) that total lipid levels remained constant within the leaves of both subspecies throughout the year. c) that storage lipid (triacylglycerols) contributed 1.4% and 4.5% to the total lipid of subspecies hermaphroditum and nigrum respectively. This data is inconsistent with the suggestion that the high leaf total lipid levels associated with alpine species represent high levels of storage lipid. Instead it is suggested that the high lipid content of Empetrum leaves may be a reflection of a well-developed waxy cuticle. It'is pseudacorus occupies habitats characterized by poor O2 availability and is able to tolerate up to two months total anoxia without any loss in viability. By contrast the cultivated Iris qerrnanica var Quechei typically a plant of well drained soils suffers 100% mortality during 8 weeks anoxia. Further the cut primary shoot of I. germanica was observed to be more susceptible to anoxic injury than the I. remainder of the rhizome. As the biosynthesis of polyunsaturated fatty acids requires the participation of molecular oxygen it was thought profitable to compare what changes occurred in the anoxia tolerant I. pseudacorus and intolerant I. germanica when subject to anoxic stress. In I. pseudocorus there were a number of lipid modification during anoxia. Glycolipids declined dramatically and although all fatty acids declined it was surprising that saturated acids decreased the most. It was suggested that the decline in glycolipids might reflect mobilization of carbohydrate reserves and/or a replenishment of the fatty acid pool through glycolipid breakdown. The significance of the alterations in membrane fluidity which might be expected to result from alterations in the saturated /unsaturated ratio remain unexplained. By complete contrast, the anoxia intolerant I. germanica although possessing a highly similar lipid profile exhibited no changes in lipid composition in response to anoxia. Therefore membrane dysfunction through lipid component omission is not a major factor in anoxic mortality. Through production of cytotoxic species such as H2O2, O2, OH and 1O2, O2 may bring about peroxidative damage. On rexposure to air it was found that the highly anoxia sensitive primary shoot tissue of I. germanica produced 38 times more malondialdehyde (M.D.A. - a lipid peroxidation product) than material which was maintained aerobically. 1. pseudacorus did not exhibit such differences. Although the overall levels of M.D.A. are higher in I. pseudacorus it may be that the primary shoot tissue contains efficient endogenous secondary protection mechanisms to make good peroxidative damage. However, in the natural environment it is unlikely that the species would ever be exposed to such rapid alterations in O2 concentrations.

The lipid composition in terms of component lipids and component acids - of farmed and wild Atlantic salmon (Salmo salar) was studied at various stages of their life cycle, up to and including sexual maturation. Lipids were extracted separately from flesh, liver and gonad organs for this study. The majority of samples examined in this work were from farmed salmon and to determine the influence of the diet on their lipid composition, a sample of the diet fed to farmed salmon was extracted and its lipids analysed. The dietary lipid is composed mainly of neutral lipids, particularly triacylglycerols, with minor amounts of polar lipids (phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol and cardiolipin).The fatty acid composition of the dietary lipid components suggested that the dietary lipid was a mixture of vegetable oils, seed oils and. fish meal(s).The major neutral lipids of salmon tissues were triacyl-glycerols, cholesterol and cholesterol esters while the dominant polar lipids were phosphatidyl choline and phosphatidyl ethanolamine, with smaller amounts of cardiolipin, phosphatidyl inositol, phosphatidyl serine and spingomyelin. The major fatty acids present in all samples examined included saturated acids (mainly 16:0 accompanied by 14:0 and 18:0), monoene acids (16:1, 18:1 and 20:1, with lower levels of 22:1 and 24:1), the n-6 group of acids, of which only 18:2 and 20:4 are consistently noticeable, and, at a much higher level, the n-3 group of acids with 22:6 > 20:5 > 22:5 >> other members. Neutral lipids (mainly TG) were highest in the flesh and least in the liver where correspondingly polar lipids (PC and PE) were highest. Variations occurred in fatty acid composition in relation to lipid class and lipid site (flesh, liver and gonads). Phosphatidyl cholines had the highest proportion of saturated acids at all three sites, whereas triacylglycerols had the highest monoene and n-6 polyene acid content. The phospholipids had very high levels of n-3 polyene acids at all three sites, whereas triacylglycerols had lower levels of these acids, although the difference was less marked in the gonads. The total lipid levels and the lipid class composition of farmed and wild salmon, all of which had spent twelve months in sea water, differed only in the gonads, where the amount of lipid in the wild salmon was greatly increased. This was reflected in a higher proportion of triacylglycerols present in the wild salmon. The major difference between the fatty acid composition of farmed and wild salmon was the higher concentration of linoleic acid in the farmed salmon triacylglycerols from all three sites compared to wild salmon triacylglycerols. This was attributed to the higher linoleic acid content in the diet of farmed salmon compared to that present in the natural marine diet. With maturation there was a decrease in the total lipid content of flesh, little change in the liver, and an increase for the gonads. The proportion of neutral lipids decreasedupon maturation, at all three sites. During the period up to and including maturation, there appeared to be selective mobilisation of the fatty acids of hepatic polar lipids, and C16 and C18 saturated and monoenoic acids increasing while the C20 and C22n-3 polyenoic acids (particularly 22:6) decreased. In the gonadal phosphatidyl cholines, maturation was accompanied by an increase in the C20 and C22n-3 polyenoic acids and a decrease in the saturated and monoenoic C16 and C 18 acids. No significant individual differences were observed in either total lipid levels or lipid composition in the flesh and liver of a group of male and female farmed salmon which originated from the same sea water pen, and had been fed the same diet.

Doctor of Philosophy / Biochemistry and Molecular Biophysics Interdepartmental Program / Kathrin Schrick / Class IV homeodomain leucine-zipper transcription factors (HD-Zip TFs) are master regulators of cell-type differentiation in the plant epidermis. These transcription factors contain a putative START (STeroidogenic Acute Regulatory (StAR)-related lipid Transfer) lipid/sterolbinding domain that is hypothesized to link metabolism to gene expression in plant development. This study is focused on two class IV family members that serve as models in many of the experiments: GLABRA2 (GL2) is a key regulator of differentiation in hair cells called trichomes as well as other epidermal cell types in various plant tissues. The second member addressed in this study is PROTODERMAL FACTOR2 (PDF2), which plays a crucial role in epidermal cell specification in shoots. A leading hypothesis is that the START domain, by binding a ligand, controls transcription factor function, analogously to nuclear receptors from mammals. Domain swap experiments indicated that the START domain from both plants and mammals is a conserved ligand-binding motif that is required for transcription factor activity. To further address its function in ligand binding, mutational analysis of the START domain of GL2 was performed. Several of the mutations remove charged residues in the predicted ligand-binding pocket and resulted in loss-of-function phenotypes, suggesting that ligand binding is critical for HD-Zip TF activity. Chromatin immunoprecipitation–based sequencing (ChIP-seq) revealed that the START domain is dispensable for transcription factor binding to DNA. Using a high throughput thermal shift assay to screen a library of pure natural compounds, specific secondary metabolites were identified as putative START domain ligands for PDF2. Experiments in both yeast and N. benthamiana demonstrated that the START domain is required for homodimerization of GL2 through its Zip domain. It was also found that the START domains physically interact with RHAMNOSE SYNTHASE I (RHM1). Further, this work provided evidence for a previously elusive redundancy between GL2 and another class IV HD-Zip TF, and unveils a positive feedback loop in the maintenance of the GL2 activity during trichome differentiation. Taken together, these findings support the premise that START domains are central players in metabolic regulatory networks that can modulate transcription factor activity by binding ligands and mediating protein-protein interactions.

Cytochrome P450 (GYP) are a family of membrane-bound enzymes which form a component of the mixed function oxidase (MFO) system and are involved in the metabolism of many endogenous and exogenous compounds and, as such, play key roles in many physiological, pharmacological and toxicological processes. Due to the diversity of their substrates, it is essential to gain an understanding of how their activities can be modulated. The membrane lipid environment of CYP isoforms has proved to be an essential component for their optimal activities and consequently investigations into this aspect of modulation are fundamental to many areas of research. The work described in this thesis investigates 3 methods for the modulation of hepatic microsomal membrane lipids in order to relate 3 components of the lipid bilayer to the associated GYP isoform activities. The effect of incubating post-mitochondrial fractions with a range of phospholipase A2 (PLA2) concentrations at 37 °G on 4 CYP-catalysed reactions during microsomal fraction preparation was examined. The size of the membrane free fatty acid (FFA) pool was found to increase substantially following PLA2 treatment, and the main hydrolysis product was revealed to be arachidonate. Although the bulk fluidity of the membrane was unchanged at specific PLA2 concentrations, differential sensitivities of the GYP isoforms were observed at these concentrations. By assaying the activity of the NADPH-P450 reductase component of the MFO independently, in addition to using an oxygen surrogate to by-pass the reductase enzyme, it was concluded that it was specifically the GYP proteins that were susceptible to the membrane modulation which consequently lead to the observed decreases in the rates of reaction. The subsequent removal of the FFA pool with bovine serum albumin (BSA) was found not to restore the GYP isoform activities. It has been suggested that the inhibitory effect of FFAs may be due to conformational changes in the lipid environment of the isozymes. Also, hydrolysis of membrane phospholipids by PLA2 activity results in the formation of FFAs and Iysophospholipids, both of which can affect substrate partitioning within a membrane. Thus, the remaining lysophospholipids following BSA treatment may have contributed to the decreased activities of the GYP isoforms. A range of PLA2 concentrations at the lower incubation temperatures of 10 °G and 20 °C were used to retailor microsomal lipids in order to investigate the possibility that the GYP activities were associated with specific lipid domains. As with the 37°G incubation, the main hydrolysis product within the FFA pool was found to be arachidonate. Although arachidonate release was not significantly affected at any of the incubation temperatures, the activities of individual GYP isoforms were significantly decreased with increases in incubation temperature at specific PLA2 concentrations. Kinetic studies suggested that PLA 2 treatment of the microsomal membrane modulated CYP activity through the hydrolysis of associated lipid domains, and not by competitive inhibition by the endogenously released arachidonate. In an attempt to elucidate it microsomal membrane fatty acid saturation affected the activities of associated CYP isoforms, a preliminary study was conducted in which membrane lipid species were chemically modified by the use of catalytic hydrogenation. Membrane fractions were successfully hydrogenated, particularly long-chain fatty acids such asarachidonate. The activities of those CYP isoforms investigated were modulated to varying degrees upon hydrogenation of the membrane environment. It was concluded that the use of such catalysts should provide a suitable system for investigations fatty acid unsaturation and CYP activities. Finally, as phosphatidylcholine (PC) has been shown to be important for certain CYP isoform activities, a preliminary study was carried out to determine the effect of the biosynthetic pathway for PC synthesis on mouse hepatic MFO activity. Using microsomal fractions obtained from a transgenic strain in which one of the pathways for PC synthesis was absent, it was found that the PC fatty acid profile was changed compared to that of the wildype fractions. Additionally, the activities of certain CYP isoforms were affected by the biosynthetic origin of PC synthesis. This sensitivity of specific isozymes to the PC biosynthetic pathway may have also been sex-dependent. The work described in this thesis suggests several strategies which could be exploited further to refine and improve experimental studies of CYP isoforms. The results obtained support the concept that the membrane composition and environment of CYP isoforms differentially affects their activities. Due to the complexity of these remarkable biochemical systems, further studies are clearly required to define the membrane properties involved in the modulation of CYP activity.

The goal of this thesis was to design, synthesize and test a chemical switch for control of membrane fusion. Control of the shape of the molecules that comprise a membrane should induce a phase change in the membrane. According to current views of membrane fusion, the phase change should also facilitate formation of fusion intermediates hence should provoke membrane fusion. The design thus focused on synthetic lipid targets that have controllable shape changes. Specifically the incorporation of the hemithioindigo (HT) photochemical switch into the fatty acid chains of phospholipids was deemed a solution to the design problem. The synthesis of four phosphatidylcholine (PC) analogues bearing two hemithioindigo moieties was accomplished. The successful synthesis starts from bromophenols. The bromide is extended to a nitrile via the Heck reaction with acrylonitrile. The thiophenol is converted to a thioindoxyl which is coupled with an aromatic aldehyde to produce the HT core. “Solventless” hydrolysis of the nitrile produces a carboxylic acid that can be coupled to a phosphoglycerol to give the target lipids. The synthetic process is both efficient and modular. All new compounds were characterized by NMR, MS and elemental analysis. The photochemistry of various HT derivatives was studied to confirm the expected photoisomerization in both homogenous solutions and vesicle bilayers. Although the UV-Vis spectra become rather insensitive to the presence of different isomers, there is evidence to confirm the Z-E switching in a range of organic solvents and in vesicles. Apparent bleaching of the HT-Iipid may indicate a photochemical dimerization reaction although isomerization would also be consistent with the data. Fusion was explored by manufacturing PS vesicles with varying concentrations and isomers of HT-lipid, and was monitored with the Terbium/Dipicolinic acid aqueous contents mixing assay (Tb/DPA assay). The sensitivity of this assay was lower than originally expected due to inner filter effects resulting in self-quenching the complex luminescence. The available data suggest that the synthetic HT-lipids disturb the membrane structure. Spontaneous fusion, apposition without metal cations, and contents leakage are some of the observations of the complexity of this system. HT-lipids in one population of vesicles are able to interact with a second population of vesicles, presumeably via membrane mixing. These results confirm that shape is a key factor in the integrity of membranes, and that second generation HT-lipids have the potential to control membrane fusion. / Graduate

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PART I STUDIES ON HEART MUSCLE LIPASES The study of the role of lipids in supplying the energy requirements of the heart has attracted widespread attention, particularly within the past decade. It is now known that the heart, under normal conditions, oxidizes lipids as its main source of energy. Numerous investigators have studied the in vivo and in vitro uptake and utilization of exogenously supplied lipids in the form of triglycerides, free fatty acids and ketone bodies. However, very few have studied the utilization of endogenous lipids by the working heart. We have examined the relative importance of both endogenous glycogen and triglycerides for supplying the caloric needs of the isolated beating rat heart, and found that under the perfusion conditions used, endogenous glycogen appears to supply the initial source of energy. A lipase in rat cardiac tissue was also examined. The enzyme had a pH optimum near 6.8, and was strongly inhibited by 0.2 M NaF and by 2 x 10⁻⁴M diisopropylfluorophosphate. Most of the activity was found in the nuclear fraction of tissue homogenates. The enzyme hydrolyzed both monoolein and mono-stearin, and possessed much less activity against tripalmitin. The enzyme also rapidly hydrolyzed the monostearin component of Ediolʀ (a commercial coconut oil emulsion widely used in lipase studies), and the implications of these findings are discussed. It was concluded from these studies that a lipase other than lipoprotein lipase exists in rat myocardium. PART II STUDIES ON CYCLIC 3', 5'-NUCLEOTIDE PHOSPHODIESTERASE In recent years, the study of the role of cyclic 3', 5'-adenosine monophosphate (cyclic 3', 5'-AMP) in the regulation of several biological reactions and processes has received widespread attention. The presence of a physiological mechanism for terminating the action of cyclic 3', 5'-AMP in biological systems would therefore be expected. Indeed, an enzyme, cyclic 3', 5'-nucleotide phosphodiesterase has been shown to exist in most mammalian tissues which have been studied for its activity. The central nervous system, particularly the cerebral cortex, possesses a very high activity of this enzyme. In this study, cyclic 3', 5'-nucleotide phosphodiesterase was partially purified from rabbit brain and its properties were studied. The enzyme required Mg⁺⁺ions for activity and was inhibited by 2 x l0⁻⁴M theophylline. Cyclic 3', 5'-dAMP, cyclic 3', 5'-GMP and cyclic 3', 5'-dGMP were hydrolyzed by the brain diesterase at approximately one-half the rate at which cyclic 3', 5'-AMP was hydrolyzed. Little activity against cyclic 3', 5'-CMP, cyclic 3', 5'-dCMP and cyclic 3', 5'-TMP was detected, although cyclic 3', 5'-UMP was hydrolyzed at approximately 13% of the rate at which cyclic 3', 5'-AMP was hydrolyzed. The brain diesterase therefore possessed a high specificity for cyclic 3', 5'-nucleotides with purine bases. Optimum enzyme activity was observed near pH 7.0, and the activity was stimulated about 1.5-fold by 0.06 M imidazole. The Km value of the enzyme with cyclic 3', 5'-AMP as substrate was approximately 0.8 x 10⁻⁴M. The properties of the partially purified phosphodiesterase from brain were thus very similar to the diesterases which have been purified from beef and dog hearts. A study of the intracellular localization of the brain diesterase indicated that about 50% of the activity was located in the 105,000 x g supernate. The microsomal and mitochondrial fractions also contained considerable amounts of diesterase activity, but little activity was located in the nuclear fraction. A survey of cyclic 3', 5'-nucleotide phosphodiesterase activity in several available specimens of the plant kingdom indicated the absence of this enzyme activity in these organisms. However, appreciable levels of diesterase activity were detected in E. coli. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate