• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 53
  • 42
  • 21
  • 8
  • 8
  • 8
  • 8
  • 8
  • 8
  • 4
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 155
  • 46
  • 29
  • 29
  • 25
  • 24
  • 20
  • 17
  • 15
  • 14
  • 14
  • 13
  • 13
  • 13
  • 13
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Cyclolinopeptides in flaxseed and flaxseed products

Gui, Bo 15 June 2011
<p>Cyclolinopeptides (CLPs), a group of naturally occurring, hydrophobic, cyclic peptides in flax, have attracted a great deal of attention due to their immunosuppressive activity. The purpose of this project was to increase our understanding of the occurrence of CLPs in flaxseed, flaxseed tissues and flaxseed products.</p> <p> In the first study, systematic methods for CLP extraction, isolation, detection and quantification were developed. The solubility of CLPs in acetone led to its use as a preferred solvent for extraction of CLPs and other hydrophobic compounds from whole flaxseed. Solid phase extraction with a silica gel column followed by selective elution with organic solvents of increasing polarity enabled the isolation of a crude peptide-rich fraction. Reverse phase HPLC chromatography of peptide-rich fractions provided a method for separation and quantification of CLPs.</p> <p> In the second study, the levels of CLPs in cultivars of flaxseed were studied to determine if there was any impact of flax genotype or environment on peptide levels. The concentration of total CLPs varied from 189 µg/g (Flanders) to 303 µg/g (Somme) in the cultivars tested. Environment, cultivar and their interaction affected the observed concentration of CLPs.</p> <p> In the third study, the concentrations of CLPs in fractions produced from flaxseed were measured by HPLC in seed coat, cotyledon and oil bodies. The concentration of CLPs was higher in the cotyledon than in the seed coat. The highest CLP concentrations were found in the oil bodies.</p> <p> In the fourth study, CLP levels in flaxseed oil were measured during and after oil extraction and refining. The concentration of CLPs was higher in expeller-extracted crude oil and solid foots and lower in flaxseed meal. A comparison of CLP levels in flaxseed oil extracted with a small expeller and in commercially-produced flaxseed oil was performed. Crude flaxseed oil produced with a small expeller had higher levels of peptides than were observed in commercial flaxseed oil available at a local retail health food store. The effect of oil refining processes, including acid degumming and alkali refining on CLP stability, was studied. Acid degumming using 1% H3PO4 effectively removed all CLPs. Alkali refining was also demonstrated as being effective at decreasing levels of CLPs, although it failed to remove all peptides.</p>
2

Cyclolinopeptides in flaxseed and flaxseed products

Gui, Bo 15 June 2011 (has links)
<p>Cyclolinopeptides (CLPs), a group of naturally occurring, hydrophobic, cyclic peptides in flax, have attracted a great deal of attention due to their immunosuppressive activity. The purpose of this project was to increase our understanding of the occurrence of CLPs in flaxseed, flaxseed tissues and flaxseed products.</p> <p> In the first study, systematic methods for CLP extraction, isolation, detection and quantification were developed. The solubility of CLPs in acetone led to its use as a preferred solvent for extraction of CLPs and other hydrophobic compounds from whole flaxseed. Solid phase extraction with a silica gel column followed by selective elution with organic solvents of increasing polarity enabled the isolation of a crude peptide-rich fraction. Reverse phase HPLC chromatography of peptide-rich fractions provided a method for separation and quantification of CLPs.</p> <p> In the second study, the levels of CLPs in cultivars of flaxseed were studied to determine if there was any impact of flax genotype or environment on peptide levels. The concentration of total CLPs varied from 189 µg/g (Flanders) to 303 µg/g (Somme) in the cultivars tested. Environment, cultivar and their interaction affected the observed concentration of CLPs.</p> <p> In the third study, the concentrations of CLPs in fractions produced from flaxseed were measured by HPLC in seed coat, cotyledon and oil bodies. The concentration of CLPs was higher in the cotyledon than in the seed coat. The highest CLP concentrations were found in the oil bodies.</p> <p> In the fourth study, CLP levels in flaxseed oil were measured during and after oil extraction and refining. The concentration of CLPs was higher in expeller-extracted crude oil and solid foots and lower in flaxseed meal. A comparison of CLP levels in flaxseed oil extracted with a small expeller and in commercially-produced flaxseed oil was performed. Crude flaxseed oil produced with a small expeller had higher levels of peptides than were observed in commercial flaxseed oil available at a local retail health food store. The effect of oil refining processes, including acid degumming and alkali refining on CLP stability, was studied. Acid degumming using 1% H3PO4 effectively removed all CLPs. Alkali refining was also demonstrated as being effective at decreasing levels of CLPs, although it failed to remove all peptides.</p>
3

Responses of linseed to vesicular-arbuscular mycorrhizae, phosphorus and zinc in a vertisol /

Seymour, Nicole Pamela. January 2002 (has links) (PDF)
Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.
4

The composition of flaxseed mucilage

Crowder, John Alexander January 1930 (has links)
No description available.
5

The composition and structure of the mucilage from the seed of the flax plant, Linum usitatissimum

Lowe, Harry Joseph, 1919- January 1945 (has links)
No description available.
6

Phase I and II enzyme induction and inhibition by secoisolariciresinol diglucoside and it's aglycone

Boyd, Erin Margaret Rose 27 April 2007
The flaxseed lignan, secoisolariciresinol diglucoside (SDG), and its aglycone, secoisolariciresinol (SECO), have demonstrated benefits in the treatment and/or prevention of cancer, diabetes and cardiovascular disease. In order for the lignans to be used therapeutically, the safety of administration alone and in conjunction with other drugs must be determined. The primary cause of drug interactions is induction and inhibition of cytochrome P450 (CYP) and phase II enzymes. A preliminary screen was conducted to assess the potential for SECO and SDG to cause CYP inhibition. A method was established to assess for CYP, glutathione-S-transferase (GST) and uridine diphosphate-glucuronosyltransferase (UGT) induction in rat primary hepatocytes by real-time reverse transcription-polymerase chain reaction (RT-PCR).<p>Preliminary assessments of inhibition measured the metabolism of testosterone to 6β-, 16α- and 2α-hydroxytestosterone, which corresponds to CYP3A, 2B/2C11 and 2C11 enzyme activity in rat hepatic microsomes by a validated high performance liquid chromatography (HPLC) method. Irreversible inhibition studies found that SDG is not an inhibitor of these isoforms up to 1000 μM. Secoisolariciresinol caused reversible inhibition of 6β-hydroxytestosterone at all testosterone concentrations, with an IC50 (inhibitor concentration causing 50% inhibition of enzyme) between 400 and 800 μM. Over the range of SECO concentrations tested, 10 1600 μM, 6β-hydroxytestosterone formation was reduced to 95 29% of control levels at 50 μM testosterone.<p>Secoisolariciresinol caused a concentration-dependent increase in 16α-hydroxytestosterone formation at 50 μM testosterone. At 10 μM SECO, there was 90% of control activity, but at 1600 μM metabolite formation was 172% of control. The formation of 2α-hydroxytestosterone was not affected at any testosterone or inhibitor concentration. Thus, SECO appears to be a CYP3A inhibitor and a CYP2B activator at testosterone KM levels. The mechanism of reversible inhibition could not be determined due to the possibility of non-Michaelis-Menten kinetics observed with CYP3A inhibition and CYP2B activation. <p>The gold standard in vitro model to assess induction is primary hepatocytes. A method was established that allowed for the isolation and culture of these cells. Positive controls caused induction of CYP mRNA levels after 24 hours treatment, demonstrating the ability of enzyme induction in the test system. Primers for real-time RT-PCR were designed that amplified CYP1A1, 1A2, 2B1, 2C11, 2C13, 2D1, 2D2, 3A1 and 3A2, GSTA2, A5 and P1, and UGT1A1, 1A7, 1A8, 2B1 and 2B12 genes. A preliminary assessment of transcriptional upregulation of drug metabolizing enzymes by SECO and SDG can be assessed in isolated and cultured rat primary hepatocytes.
7

Effects of dietary oils low in n-6:n-3 fatty acid ratio on cardiovascular risk in mice: the impact of the source of n-3 fatty acids

Riediger, Natalie Diane 16 September 2008 (has links)
The impact of the source of n-3 fatty acids on cardiovascular disease has not been fully investigated. This study was carried out to investigate cardiovascular benefits of diets with a low ratio (2:1) of n-6:n-3 fatty acids from different sources, either fish or flaxseed oil, in C57BL/6 mice. Twenty-one mice were divided into 3 groups (n=7) and fed an atherogenic diet supplemented with either a fish or flaxseed oil-based ‘designer oil’ with low n-6:n-3 fatty acid ratio (treated groups) or safflower oil-based formulation with a high ratio (control group) for 16 weeks. Plasma cholesterol levels declined significantly in both treated groups, by greater than 30%, compared to those in control. The ratio of n-6:n-3 fatty acids in liver was significantly lower in fish and flax groups as compared to control. Our data suggest that lowering dietary ratio of n-6:n-3 fatty acids may significantly reduce cardiovascular risks regardless of the source of n-3 fatty acids. / October 2008
8

Pharmacokinetic and pharmacodynamic studies on flaxseed lignans

2013 January 1900 (has links)
Natural Health Products (NHPs) are regulated and require safety and efficacy information for their approval into the Canadian market. Flaxseed lignans are NHPs with putative health benefits in a number of chronic diseases. In the flaxseed the principal lignan is secoisolariciresinol diglucoside (SDG). After oral consumption SDG is converted into its aglycone secoisolarisiresinol (SECO) and subsequently into mammalian lignans (enterodiol (ED) and enterolactone (EL)) in the presence of gastrointestinal microflora. In my Ph.D. research, I conducted a series of in vitro and in vivo PK studies to enable the design of prospective safety and efficacy studies of lignans. In vitro PK studies in the Caco-2 cell monolayer suggest that SDG has poor intestinal permeation and intestinal conjugation characteristics (glucuronidation and sulphation); however, SECO, ED and EL undergo passive permeation and extensive conjugation (SECO<ED<EL) by Caco-2 cells. Single oral and intravenous dose pharmacokinetics in male Wistar rats showed that these lignans exhibit high volumes of distribution, high systemic clearance values, and short half-lives. EL was fatal to the rats at the given intravenous and oral doses while SDG was not orally bioavailable and may not likely be the bioactive lignan form. I investigated the effect of acute SDG and chronic BeneFlax oral administration in blunting the postprandial hyperglycemia in healthy and streptozotocin induced male Wistar type II diabetic rats, respectively; however, my pilot study failed to show any change in postprandial blood glucose levels. Further, I conducted selective cytotoxicity evaluations in prostate and breast cancer cell lines. Only EL caused selective cytotoxicity of breast and prostate cancer cells with IC50 values that may be physiologically achievable. To elucidate the mechanism of action, I tested concentration and time dependent effects of EL on various enzymes and transcription factors of fatty acid metabolism at mRNA and protein levels in cancer (PC-3) and normal (RWPE-1) prostate cell lines. mRNA and protein expression analysis showed a concentration and time dependent inhibition of fatty acid synthase (FAS) and suggested that EL may inhibit FAS to show anti-proliferative effect on prostate cancer. The pharmacokinetic characteristics and pharmacodynamics properties of flaxseed lignans warrant their further investigation.
9

Phase I and II enzyme induction and inhibition by secoisolariciresinol diglucoside and it's aglycone

Boyd, Erin Margaret Rose 27 April 2007 (has links)
The flaxseed lignan, secoisolariciresinol diglucoside (SDG), and its aglycone, secoisolariciresinol (SECO), have demonstrated benefits in the treatment and/or prevention of cancer, diabetes and cardiovascular disease. In order for the lignans to be used therapeutically, the safety of administration alone and in conjunction with other drugs must be determined. The primary cause of drug interactions is induction and inhibition of cytochrome P450 (CYP) and phase II enzymes. A preliminary screen was conducted to assess the potential for SECO and SDG to cause CYP inhibition. A method was established to assess for CYP, glutathione-S-transferase (GST) and uridine diphosphate-glucuronosyltransferase (UGT) induction in rat primary hepatocytes by real-time reverse transcription-polymerase chain reaction (RT-PCR).<p>Preliminary assessments of inhibition measured the metabolism of testosterone to 6β-, 16α- and 2α-hydroxytestosterone, which corresponds to CYP3A, 2B/2C11 and 2C11 enzyme activity in rat hepatic microsomes by a validated high performance liquid chromatography (HPLC) method. Irreversible inhibition studies found that SDG is not an inhibitor of these isoforms up to 1000 μM. Secoisolariciresinol caused reversible inhibition of 6β-hydroxytestosterone at all testosterone concentrations, with an IC50 (inhibitor concentration causing 50% inhibition of enzyme) between 400 and 800 μM. Over the range of SECO concentrations tested, 10 1600 μM, 6β-hydroxytestosterone formation was reduced to 95 29% of control levels at 50 μM testosterone.<p>Secoisolariciresinol caused a concentration-dependent increase in 16α-hydroxytestosterone formation at 50 μM testosterone. At 10 μM SECO, there was 90% of control activity, but at 1600 μM metabolite formation was 172% of control. The formation of 2α-hydroxytestosterone was not affected at any testosterone or inhibitor concentration. Thus, SECO appears to be a CYP3A inhibitor and a CYP2B activator at testosterone KM levels. The mechanism of reversible inhibition could not be determined due to the possibility of non-Michaelis-Menten kinetics observed with CYP3A inhibition and CYP2B activation. <p>The gold standard in vitro model to assess induction is primary hepatocytes. A method was established that allowed for the isolation and culture of these cells. Positive controls caused induction of CYP mRNA levels after 24 hours treatment, demonstrating the ability of enzyme induction in the test system. Primers for real-time RT-PCR were designed that amplified CYP1A1, 1A2, 2B1, 2C11, 2C13, 2D1, 2D2, 3A1 and 3A2, GSTA2, A5 and P1, and UGT1A1, 1A7, 1A8, 2B1 and 2B12 genes. A preliminary assessment of transcriptional upregulation of drug metabolizing enzymes by SECO and SDG can be assessed in isolated and cultured rat primary hepatocytes.
10

The effect of flaxseed hulls on expanded corn meal products

Barron, Marc Edward 15 May 2009 (has links)
Brown flaxseed hulls were added to de-germed corn meal and processed into extrudates with acceptable texture and increased nutritional benefits. The addition of brown flaxseed hulls to a corn based expanded snack increases the dietary fiber, alpha omega 3 fatty acids, and antioxidants levels. The addition of flaxseed hulls to a corn based snack can increase its susceptibility to oxidative rancidity which can limit shelf life. Whole ground tannin sorghum with added brown flaxseed hulls was processed into extrudates and texture, antioxidant activity, and stability were evaluated. Brown flaxseed hulls were mixed with de-germed yellow corn meal in ratios of 0:100, 15:85, 20:80, and 25:75 (w/w) and extruded with 12 and 15% feed moistures using a twin screw extruder to produce direct expanded extrudates. Expansion of extrudates containing brown hulls decreased as the amount of hulls increased. Dried extrudates had acceptable flavor immediately after processing. Total phenols and antioxidant activity of extrudates containing 20 and 25% brown flaxseed hulls, extruded at 15% feed moisture were higher than de-germed corn meal extruded at 16% feed moisture. Brown flaxseed hulls were added at 20% to whole ground white and sumac (tannin) sorghums and processed into extrudates. Expansion increased for sorghum extrudates containing brown flaxseed hulls. The addition of brown flaxseed hulls increased antioxidant activity and total phenols of both white and sumac (tannin) extrudates. The sumac (tannin) extrudates had the longest delay in producing off odor (paintlike odor) and had the lowest p-Anisidine values compared to white (ATX631x RTX 436) sorghum and corn meal with added flaxseed hulls. Corn meal extrudates with 20% brown flaxseed hulls produce off odors more rapidly than other extrudates. This suggests that the tannins in sorghum maybe extending shelf life because of their antioxidant activity. The addition of brown flaxseed hulls can be used to increase nutritional value and antioxidant levels in a direct expanded product. Also the use of tannins sorghums in products containing flaxseed may help delay oxidation, thus preventing the occurrence of off odors. Further work needs to be done to verify results.

Page generated in 0.0504 seconds