Association mapping (AM), based on linkage disequilibrium, is a complementary strategy to traditional quantitative trait loci (QTL) mapping for describing associations between genotypes and phenotypes in crop plants. Yellow endosperm colour, an important quality trait in durum wheat (<i>Triticum turgidum L. var. durum</i>), was studied to determine the potential of AM to (1) identify previously reported QTL using a genome wide scan and (2) to determine allelic association of the phytoene synthase 1 (Psy1) gene using a candidate gene analysis. At present, a number of QTL for endosperm colour have been identified, and phytoene synthase, the initial enzyme of the carotenoid biosynthetic pathway, has been associated with QTL on the group 7 chromosomes which are considered to play a significant role in expression of yellow pigment concentration. CIE 1976 b*, a light reflectance measurement, and water-saturated butanol extracted pigments were assessed on a collection of 93 elite accessions from a variety of geographic origins, and genotyped with 245 markers. Population structure was assessed using genetic distance and Bayesian model based approaches, identifying five sub-populations consistent with breeding origin and pedigree. Association analysis identified significant associations with yellow endosperm colour on all chromosomes, including several previously identified QTL as well as new regions for genomic dissection. Pairwise LD mapping of Psy1-B1 and Psy1-A1 located the genes to chromosomes 7B and 7A respectively, to regions which have previously been identified for yellow pigment concentration QTL. The results of this study indicate that AM can be used to complement traditional QTL mapping techniques, and identify novel QTL for further study.

Giloma derive from glial cell, which is the most common malignant and deadly primary tumor that affects the brain and nervous system, and the possible causes are not fully understood. Glioma cells are highly invasive, and can spread to distant area of the brain, this invasive behavior makes complete tumor debulking virtually impossible. Glioma even resists to high dose of radiotherapy and chemotherapy, the prognosis of malignant glioma remains dismal and the estimated median survival time is 12¡Ð15 months. The previous studies showed that the interaction of hyaluronan (HA), the abundant component of the ECM in the adult central nervous system, with cell-surface receptors, CD44 is able to mediate motility, tumor formation and multidrug resistance of glioma. In addition, the interacted between HA and CD44, that could up-regulate glioma HA production. But the effect of hyaluronan synthases (HAS) expression in this regulation mechanism was not described clearly. In this study, the HAS expression was a target gene in the rat glioma cell line¡ÐC6 on the conditions of HA addition or cd44 gene silence, respectively. The results showed that HA addition increased the HAS expression, and cd44 gene silence caused the less expression of HAS, and which could restored by HA addition. Futher, the HA addition could prolong cell proliferation , decrease the expression of the CD44 and GFAP, the astrocyte differentiation marker, and increase brain tumor stem cell marker¡Ðnestin expression, and this result could reappear by the cd44 gene silence alone. However, instead the stemness of cell, the cell toward differentiation and proliferation by HA addition after the cd44 gene silence. From those results, the interaction between HA and CD44 could exist the positive feedback to trigger the HA production, and HA could regulate cells proliferation and differentiation by interaction with CD44 in the glioma cells.

Aging is associated impaired endothelial function in the skeletal muscle vasculature which contributes to decreased ability to increase muscle blow during exercise. This endothelial dysfunction is mediated, primarily, by impairments in the nitric oxide (NO) pathway in the skeletal muscle vasculature. The major purpose of this dissertation is to determine the mechanisms that mediate age-related endothelial dysfunction in rat soleus feed artery (SFA) and determine whether exercise training ameliorates this impairment in endothelial function. Therefore in these series of studies we sought to test three major hypotheses: 1) That exercise training reverses age-related decrements in endothelium-dependent dilation in SFA and that this improved endothelium-dependent dilation is the result of increased NO bioavailability due to increased content and phosphorylation of eNOS and/or increased antioxidant enzyme content; 2) That age-related endothelial dysfunction in rat SFA is mediated in part, by NAD(P)H oxidase-derived reactive oxygen species (ROS); 3) and, that impaired endothelium-dependent dilation in senescent SFA is due to an impaired potential for p-eNOSser1177. To test these hypotheses, SFA from young (4 month) and old (24 month) Fischer 344 rats were isolated for either determination of endothelium-dependent and –independent dilations or biochemical analyses. Results from these investigations suggest that 1) exercise training reverses the detrimental effects of aging on endothelial function in skeletal muscle feed arteries by enhancing the capacity to scavenge superoxide, increasing the bioavailability of NO; 2) ROS contribute to impaired endothelium-dependent dilation in old SFA; whereas, ROS appear to play a role in ACh-mediated dilation in SFA from young rats; 3) and, that the PI3 kinase/protein kinase B (Akt)/eNOS pathway is preserved with age.

Environmental factors such as ambient temperature and oxygen availability are variation in different altitude. Individuals within a species, living in variable environments often display phenotypic plasticity by changing morphology, behavior, reproduction, and physiology to meet the individual¡¦s ability to survive demanding conditions. This study was aimed to investigate the expression of angiotensin receptor and nitric oxide synthase genes of individuals resided at differential altitude, in an attempt to find the role of these molecules in cardiovascular adaptation to altitude. Spiny rats (Niviventer coxingi) are widely elevational distributed in Taiwan. They were studied under more natural conditions to provide an ecological context data on physiological plasticity between the different altitudes. I examined the body weight, blood pressure, heart rate and the expression of angiotensin type 1 or type 2 (ATI or ATII) receptor and nitric oxide synthase (NOS) genes in tissues (cortex, hypothalamus, medulla, lung, heart, aorta, adrenal gland and kidney) of spiny rats resided at differential altitude and during the domesticated period. The results of the study showed that spiny rats resided at higher altitudes were lighter than that at lower altitudes (750 m: 178.6¡Ó35.8 g and 1600 m: 122.3¡Ó29.3 g). Spiny rats resided at 1600 m did not change their body weight during the domesticated period, but rats resided at 750 m gradually reduced their body weight. Blood pressure and heart rate were similar between rats resided at different altitudes, and did not change during the domesticated period. ATI receptor, endothelelial NOS (eNOS), inducible NOS (iNOS) and neuronal NOS (nNOS) mRNA expression in these tissues were similar between rats resided at different altitudes. ATII receptor mRNA expressed in these tissues under our detection limit. Rats resided at 750 m declined the level of nNOS in heart, when they were domesticated at 100 m. ATI receptor in kidney reduced at first, but subsequently increase to same level like native. Moreover, rats resided at 1600 m declined the level of iNOS in heart, when they were domesticated at 100 m. Together, these results indicate that heart rate, blood pressure, ATI receptor, eNOS, iNOS and nNOS mRNA expressions in these tissues were similar between rats resided at different altitudes. If there was no other compensatory mechanism, individuals resided at higher altitude were limited in low available oxygen. A reduced body weight could help in adaptation to high-altitude.

Obesity is a disorder of energy imbalance and the most prevalent nutritional diseases in developed countries. Besides, obesity is also strongly associated with health problems such as type 2 diabetes (NIDDM), hypertension, hyperlipidaemia, cardiovascular diseases and cancers. However, the defects in lipid metabolism underlying obesity-related disorders are extremely complicated. Thus, extensive studies on the mechanism of endogenous fatty acids synthesis would be one of the keys to elucidate molecular pathogenesis of obesity. In liver or adipose, fatty acid synthase (FAS) utilizes acetyl-CoA, malonyl-CoA and NADPH to synthesize long-chain fatty acids (C16 or C18), which can be converted to triglycerides and stored as fat. During lactation, thioesterase II (TE II) expresses in mammary glands and interacts with FAS to produce medium-chain fatty acid (primarily C10) in milk, which provides immune protection and energy for the newborn. TE II causes premature termination of fatty acid synthesis catalyzed by FAS and releases medium-chain fatty acids. Unlike long-chain fatty acids, medium-chain fatty acids can enter mitochondria directly for beta-oxidation to generate ATP, thus provide energy more efficiently. Since TE II gene expression is under strict regulation, we utilized adenovirus gene transfer techniques to deliver and express TE II in hepatocytes. It was postulated that expression of TE II in hepatocytes might result in the increase of ATP and reduction of long-chain fatty acids, subsequently decrease the fat production. Recombinant adenovirus was used as gene delivery system for TE II because of its high titer, wide host range, and transduction efficiency. In the present study, we have generated and characterized the recombinant Ad-TE II by PCR, western blot analysis, and enzymatic assay, respectively. By using Ad-GFP, we have determined the optimal multiplicity of infection (MOI) for adenovirus to infect HepG2 cells is about 100-200. Adenovirus-mediated TE II expression in hepatocytes was demonstrated by western blot as well as TE II enzymatic assay. We have demonstrated that the adenovirus-mediated TE II expression was slightly cytotoxic to hepatocytes. Besides, an increase of free fatty acids, asparate transaminase, lactate dehydrogenase levels, as well as ATP synthesis was also noted in the TE II-expressed hepatocytes. The enhanced the release of asparate transaminase (AST/GOT) and lactate dehydrogenase (LDH) after TE II expression in the hepatocytes further supported its cytotoxcity to hepatocytes. In the future, we will carry out experiments to further characterize the effects of TE II expression on cellular lipid metabolism through adenovirus gene delivery. We hope that the present studies will not only provide further insights into mammalian lipid metabolism, but also enable us to evaluate the therapeutic potential of TE II on the treatment of obesity and its related disorders.

[N,N??-bis-(mercaptoethyl)-1,5-diazacyclooctanato]NiII, Ni-1, is known to undergo metallation reactions with numerous metals. [N,N??-bis-(mercaptoethyl)-1,5-diazacycloheptanato]NiII, (bme-dach)Ni or Ni-1??, differs from Ni-1 by one less carbon in its diazacycle backbone ring producing subtle differences in N2S2Ni geometry. Metallation of Ni-1?? with PdCl2, Pd(NO3)2, and NiBr2 produced three structural forms: Ni2Pd basket, Ni4Pd2 C4-paddlewheel, and Ni3 slant chair. In attempts to provide a rationale for the heterogeneity in the active site of Acetyl coA Synthase, metal ion capture studies of Ni-1 in methanol found a qualitative ranking of metal ion preference: Zn2+ < Ni2+ < Cu+. Formation constants for metal ion capture of Ni-1?? in water were determined for Pb2+, Ni2+, Zn2+, Cu+, and Ag+. A quantitative estimate places copper some 15 orders of magnitude above nickel or zinc in binding affinity. Sulfur dioxide uptake by Ni-1?? is characterized by significant color change, improved adduct solubility, and reversible binding of two equivalents of SO2. These combined properties establish Ni-1?? as a suitable model for gas uptake at nickel thiolate sites and as a possibly useful chemical sensor for this poisonous gas. Comparisons of molecular structures,&#61472; &#957;(SO) stretching frequencies, and thermal gravimetric analyses are made to reported adducts including the diazacyclooctane derivative, Ni-1&#903;2SO2. Visual SO2 detection limits of Ni-1 and Ni-1?? are established at 25 ppm and 100 ppm, respectively. Structural studies of products resulting from reaction at the nucleophilic S-sites of (bme-dach)Ni and [(bme-dach)Zn]2 included acetyl chloride and sodium iodoacetate as electrophiles are shown. The acetyl group is a natural electrophile important to the citric acid cycle. Acetylation of (bme-dach)Ni produces a five coordinate, paramagnetic species. Iodoacetate is a cysteine modification agent known to inhibit enzymatic activity. The reaction of (bme-dach)Ni and sodium iodoacetate yields a blue, six coordinate nickel complex in a N2S2O2 donor environment. The bismercaptodiazacycloheptane ligand binds lead(II) forming an unprecedented structural form of N2S2M dimers, in which Pb2+ is largely bound to sulfur in a highly distorted trigonal geometry. Its unusual structure is described in comparison to other derivatives of the bme-daco ligand. The synthesis and structural characterization of square pyramidal (bme-dach)GaCl are also given and compared to the analogous (bme-daco)GaCl.

The A-cluster of acetyl-CoA synthase (ACS) catalyzes the formation of acetyl- CoA from CO, coenzyme-A, and a methyl group donated by a corrinoid iron-sulfur protein. Recent crystal structures have exhibited three different metals, Zn, Cu, and Ni, in the proximal site, which bridges a square-planar nickel site and a [Fe4S4] cubane. Contradicting reports supported both the nickel and copper containing forms as representing active enzyme. The results presented here indicate that copper is not necessary or sufficient for catalysis and that copper addition to ACS is deleterious. Several proposed mechanisms exist for the synthesis of acetyl-CoA, the two most prominent are the ‘paramagnetic’ and ‘diamagnetic’ mechanisms. The ‘diamagnetic’ mechanism proposes a two electron activation that precedes methylation to produce an EPR silent Ni2+-CH3 species. This then reacts with CO and coenzyme-A to form acetyl- CoA and regenerate the starting species. The ‘paramagnetic’ mechanism assumes a one electron activation prior to the methylation of the paramagnetic Ni1+-CO state to form an unstable Ni3+-acetyl species. This is immediately reduced by an electron shuttle. Results are presented here that no shuttle or external redox mediator is necessary for catalysis. This supports the ‘diamagnetic’ mechanism, specifically that a two-electron reductive activation is necessary and that the Ni1+-CO species is not an intermediate. The two-electron reductive activation required by the ‘diamagnetic’ mechanism results in an unknown electronic state. Two proposals have been made to describe this form of the A-cluster. The first hypothesis from Brunold et al involves a one-electron reduction of the [Fe4S4]2+ cube and a one-electron reduction of the Nip 2+. This should result in a spin-coupled state that is S = integer. The Ni0 hypothesis requires both electrons to localize on the Nip 2+ forming a zero-valent proximal nickel. Mössbauer spectroscopy has been used to probe the oxidation state and spin state of the [Fe4S4] cube in the reduced active form. No integer spin system is found and this is interpreted as supporting the Ni0 hypothesis. Additionally, spectra are presented that indicate the heterogeneous nature of the A-cluster is not caused by the occupancy of the proximal site.

Electronic and steric parameters for square planar NiN2S2 complexes as bidentate, S-donor ligands have been established. According to the (CO) stretching frequencies and associated computed Cotton-Kraihanzel force constants of (NiN2S2)W(CO)4 adducts, a ranking of donor abilities and a comparison with classical bidentate ligands are as follows: Ni(ema)= > { [NiN2S2]0 } > bipy phen > Ph2PCH2CH2PPh2 > Ph2PCH2PPh2. In addition, we have demonstrated that the NiN2S2 ligands are hemilabile as evidenced from CO addition to (NiN2S2)W(CO)4, which is in equilibrium with the resulting (NiN2S2)W(CO)5 species (Keq = 2.8 M-1, G = -1.4 kJ/mole at 50C). Complete NiN2S2 ligand displacement by CO-cleavage of the remaining W-S bond to form W(CO)6 was not observed, indicating that the remaining W-S bond is considerably strengthened upon ring-opening. Several new cluster compounds based on the NiN2S2 ligands bound to CuI, RhI, PdII and W0 are reported. Structural analysis of (NiN2S2)MLn complexes show a unique structural feature defined by the dihedral angle formed by the intersection of NiN2S2/WS2C2 planes; placing the NiN2S2 ligand in closer proximity to one side of the reactive metal center. This unique orientational feature of the NiN2S2 ligands in the series of bimetallic compounds contrasts with classical diphosphine or diimine ligands. The "hinge angle" ranges in value from 136 as in the (Ni-1*)W(CO)4 to 101 in the (Ni-1)Pd(CH3)(Cl) complexes. The rigidity of the SR hinge of the nickeldithiolate ligands suggests that they might be suitable for stereochemical and regioselective substrate addition to catalytically active metals such as RhI and PdII.. The structural as well as functional similarities of the acetyl CoA synthase enzyme (ACS) and a palladium-metal based industrial type catalyst led to the preparation of a [(Ni-1)Pd(CH3)]+ bimetallic complex. This complex facilitates CO and ethylene copolymerization to produce polyketone similar to conventional (diphosphine)Pd(X)2 catalysts. However, the diphosphine ligands produce more efficient catalysts as the electron-rich character of the NiN2S2 ligand favors the resting state of the catalyst, [(Ni-1)Pd(C(O)CH3)(CO)]+, over the reactive form (Ni-1)Pd(C(O)CH3)(2-C2H4)]+. An exploratory investigation with the Ni-Pd heterobimetallic showed that this complex also facilitated the C-S coupling reaction to form a thioester similar to the ACS enzyme.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from PDF title page (viewed Feb. 4, 2010). Additional advisors: Subramaniam Ananthan, David E. Graves, Craig D. Smith, Sadanandan E. Velu. Includes bibliographical references.

The production of new drugs as potential pharmaceutical targets is arguably one of the most important avenues of medicine, as existing diseases not only require treatment, but it is also certain that new diseases will appear in the future which will need treatment. Indeed, existing medicines such as antibiotics and immunosuppressants maintain their current activities in their respective realms, yet the molecular and stereochemical complexity of these compounds cause a burden on organic synthetic chemists that may prohibit the high yields required to manufacture a drug. The enzyme systems that naturally manufacture these compounds are incredibly efficient in doing so, and also do not use environmentally harmful solvents, chiral auxiliaries, or metals that are utilized in the current syntheses of these compounds; therefore utilizing these enzymes' machinery for the biocatalysis of new medicinally-relevant compounds, as researchers have in the past, is undeniably a rewarding endeavor. In order to harness these systems' biocatalytic potential, we must understand the processes which they operate. This work focuses on ketoreductase domains, since they are responsible for setting most of the stereocenters found within these complex secondary metabolites. We have supplied a library of substrates to multiple ketoreductases to test their limits of stereospecificity and found that, for the most part, they maintain their natural product stereospecificity seen in nature. We were even able to convert a previously nonstereospecific ketoreductase to a stereospecific catalyst. We have also developed a new technique to follow ketoreductase catalysis in real-time, which can also differentiate between which diastereomeric product is being produced. Finally, we have elucidated the structure of a ketoreductase that reduces non-canonically at the [alpha]- and [beta]- position, and functionally characterized its activities on shortened substrate analogs. With the knowledge gained from this dissertation we hope that the use of ketoreductases as biocatalysts in the biosynthesis of new natural product-based medicines is a much nearer reality than before. / text