Browsing by Subject "Lipids"
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Item Consumer assessment and objective measures of beef flavor of four beef muscles from USDA choice and select graded carcasses(2013-08) Hunt, Mary R.; Miller, Markus F.; Brooks, Chance J.; Rathmann, Ryan J.A consumer study was conducted in Lubbock, Texas, to measure the effects of quality grade on the palatability traits of flavor, tenderness, juiciness, and overall liking of four beef muscles. The study was arranged as a 2 × 4 factorial representing two quality grade categories [Upper 2/3 (Top) Choice and Select] and four muscles [longissimus lumborum (LL), gluteus medius (GM), serratus ventralis (SV), and semimembranosus (SM)]. Sides (n = 40; 20 per quality grade category) of beef were selected from a commercial processing facility by trained Texas Tech University personnel to obtain subprimals containing the four muscles. Proximate analysis was conducted on each subprimal to determine percentage fat, moisture, protein, and collagen. Plus, fatty acid content (n = 48) and volatile analysis of cooked samples (n = 40) were analyzed for each treatment group. The muscles were then fabricated into 2.5-cm steaks, and further processed into 5 × 5 cm pieces. Consumers (n = 120) rated eight steak samples, one per treatment group, for tenderness, juiciness, flavor liking, and overall liking and rated each trait as either acceptable or unacceptable. According to proximate analysis means, SV had more desirable (P < 0.01) fat percentage (9.7%) than any other muscle and SM had the least (2.5%); while LM (4.9%) and GM (5.1%) were intermediate. Regardless of muscle, Upper 2/3 Choice had more desirable (P < 0.01) fat percentage (7.1%) than Select (4.0%). An interaction between muscle and quality grade was observed (P < 0.05) for juiciness, flavor liking, and overall liking. For juiciness, Upper 2/3 Choice SV had the most desirable (P = 0.02) consumer scores than any other muscle × quality grade combination. SM had the least juiciness scores, regardless of quality grade, which did not differ (P > 0.05). Consumer flavor liking and overall liking score exhibited similar trends indicating Upper 2/3 Choice LL, GM, and SV had more desirable (P < 0.02) scores than the remaining muscle × quality grade combinations. Consumer scores for flavor liking and overall liking for all muscles, except SM, were more desirable for Upper 2/3 Choice compared to Select. Similarly, tenderness scores were more desirable (P < 0.01) for Upper 2/3 Choice compared to Select, regardless of muscle. Consumers rated LL as more tender (P < 0.05) than SV and SM, but similar to GM (P = 0.52). Consumers scored the tenderness of SM less desirable (P < 0.01) compared to all other muscles. A decrease (P < 0.05) in consumer acceptability of each palatability trait was observed as quality grade decreased from Upper 2/3 Choice to Select. The SM showed the least acceptability scores for all the palatability traits. Overall and flavor acceptability were similar (P > 0.05) between LL, GM, and SV regardless of quality grade. Consumer overall liking was correlated (P < 0.01) with consumer tenderness (r = 0.75) and juiciness (r = 0. 68) ratings, but most highly correlated with flavor liking (r = 0.85). Results for fatty acids showed PUFA negatively affected consumer perceived flavor and overall liking in neutral lipid (NL) fractions. Within polar lipid (PL) fractions, linoleic acid (18:2)(r = -0.36) and Dihomo-gamma-linolenic acid (20: 3n6)(r = -0.30)], know for negative flavor properties, were shown to negatively correlated with flavor. Additionally, as fat percentage increased NL and PL concentration increased linearly. There were 42 volatile compounds detected in the headspace of cooked steak samples. The majority detected were classified as aldehydes. Very few volatile compounds correlated with consumer palatability scores. When tenderness was acceptable, flavor and juiciness play a major role in determining overall acceptability. Even when consumers scored tenderness low, as with the SM, superior flavor and juiciness could compensate and improve the overall liking and acceptability of beef. Overall liking of SV and GM from high quality carcasses was superior to LL from lower quality carcasses and comparable to LL from high quality carcasses. Therefore, results from this study showed additional value could be captured by marketing more underutilized cuts from the chuck and sirloin of high quality carcassesItem Dietary lipid modulation of immune parameters in burn and sepsis(Texas Tech University, 1994-12) Penturf, Mary Ellen HiseTwo experiments were conducted to obtain further information on dietary lipid modulation of immune function in metabolic stress conditions. In the first experiment, the objective was to modify dietary lipid composition of animal diets in order to evaluate plasma membrane changes and immunological parameters during sepsis. The second experiment was conducted to determine the effect of an essential fatty acid deficient diet on immunological response during postburn injury.Item Effect of diabetes on composition and metabolism of heart lipids(Texas Tech University, 1980-08) Paulson, Dennis JNot availableItem Elucidating the Role of Yeast Lipin (PAH1) in Lipid Droplet Biogenesis(2012-07-17) Adeyo, Oludotun; Goodman, Joel M.Lipid droplets are unique organelles important for a host of cellular functions including the storage of neutral lipids, but factors that regulate the biogenesis and maintenance of these organelles remain relatively unknown. The primary focus of this dissertation will be to understand the role of the phosphatidic acid hydrolase (Pah1p) in the biogenesis of lipid droplets in Saccharomyces cerevisiae. Pah1p is an enzyme that converts phosphatidic acid to diacylglycerol, and its absence or elimination of its catalytic activity results in the accumulation of neutral lipids within membranes of the endoplasmic reticulum. Furthermore, lipid droplet formation is facilitated by diacylglycerol through a mechanism that appears to be independent of diacylglycrol’s role as a substrate for triglyceride biosynthesis. Finally, lipid droplets originated from regions of the endoplasmic reticulum where the Pah1p activators were located. The second part of this dissertation will focus on the lipodystrophy related protein Fld1p and its association with lipid droplets. Droplets always associate with Fld1p, and in the absence of lipid droplets, Fld1p is localized as patches distributed throughout the endoplasmic reticulum. In addition, induced lipid droplets originate from these Fld1 patches. I conclude from this work that diacylglycerol facilitates lipid droplet formation and that Fld1p is somehow involved in the biogenesis or maintenance of these organelles. [Keywords: Lipid droplet, Diacylglycerol, lipin, steryl esters, endoplasmic reticulum, Triacylglycerol, phosphatidic acid]Item Fiber Orientation Modeling: a Method to Improve Quantitation of Intramyocellular Lipids in Human Subjects at 7 Tesla(2011-10-03T14:31:15Z) Khuu, Anthony N.; Malloy, Craig R.Background: Increased intramyocellular lipid (IMCL) content in skeletal muscle has been suggested to be a biomarker for insulin resistance. As a noninvasive method of estimating IMCL, 1H MR spectroscopy of muscle fat has been a popular method for measuring the concentration of IMCLs, a goal highly desirable for research in the pathogenesis of type 2 diabetes. Extramyocellular lipids (EMCL) are often considered to be deposited along strands that are parallel to Bo (the applied field) whereas IMCL are assumed to be spherical droplets in the muscle cells’ cytoplasm. Resolution between IMCL and EMCL signals mainly results from the angle-dependant bulk susceptibility of the 2 geometric structures. However, IMCL signal is usually contaminated by a broad and asymmetrical EMCL . Conventional fitting methods usually assume that both the IMCL and EMCL signals to be symmetrical, represented by a single Lorentzian, Gaussian or Voigt (hybrid lineshape between Gaussian and Lorentzian) lineshapes. However, significant asymmetry in the resonance assigned to the methylene protons (-CH2-)n in extramyocellular lipids (EMCL) interfered with fitting the spectra. In this work, we explore another approach, named Fiber Orientation Modeling (FOM) by using the bulk susceptibility effect theory to accurately assess the lineshape of EMCL. Methods: The distribution of EMCL strand orientation at any angle from 0 degrees to 90 degrees relative to Bo was described by a Gaussian function, centered at a specific angle and a width representing a dispersion of EMCL strands. The chemical shift OMEGA from each strand was translated by the well-known orientation dependence interaction OMEGA = 3cos2THETA-1, where THETA is the angle between EMCL and the applied field. As the result, the location and amplitude of individual curves representing each strand could be derived. Depend on the aforementioned Gaussian distribution, the combination of these individual curves generated a unique EMCL shape. In this work, spectral simulations were generated using muscle fiber orientation reported previously. The phantom experiment with a fat cylinder (representing EMCL) submerged in Intralipid(TM) solution (representing IMCL) was also performed to determine the maximal shift at 0 degrees and 90 degrees. Under IRB approval, single voxel and chemical shift images were acquired from soleus and gastrocnemius muscle of healthy human subjects at 7T (Phillips Medical system, Cleveland, Ohio). All the spectra were fitted with the hybrid Voigt lineshape and the experimental lineshape. Results: In simulated spectra with dominant angle of 00 to the applied field and little dispersion, fitting with the Voigt lineshape accurately determined IMCL/EMCL ratio over a range of different linewidths. Increasing dispersion and central angle caused overestimation of IMCL/EMCL ratios, up to three-fold when fitted with the Voigt lineshape. The error was substantially reduced using our method. The improvement is also observed in phantom spectra and human spectra. Estimates of [IMCL]/[EMCL] were significantly improved by including variations in fiber orientation in the lineshape analysis (fiber orientation modeling, FOM). Calculated soleus [IMCL] using FOM, 4.43 ± 2.32 mmol/kg wet weight, was lower compared to most previous reports in soleus. The average orientation of EMCL was calculated to be 35 degrees relative to Bo with a dispersion width of 24 degrees Conclusion: Since prominent asymmetrical EMCL signal tends to contaminate into IMCL region, this interaction results in the amplitude-dependence of IMCL signal on the average orientation and dispersion of EMCL. As the result, the use of symmetrical lineshape tends to overestimate the IMCL signal if all strands of EMCL are not parallel to Bo and one another. By accounting for the angular dispersion& orientation, the fit would improve both the residual and the IMCL estimate.Item Indicators of spoilage in Thuringer sausage(Texas Tech University, 1985-12) Subsoontorn, SirisopitNOT AVAILABLEItem Insig-Mediated Regulation of Hepatic Lipid Synthesis(2007-05-22) Engelking, Luke James; Brown, Michael S.Cholesterol synthesis in mammals is tightly regulated by end-product feedback inhibition. 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) catalyzes a rate determining reaction that is highly regulated by transcriptional and post-transcriptional mechanisms. As cellular cholesterol accumulates, the transcription of HMGR mRNA is suppressed and the proteosomal degradation of HMGR protein is accelerated. The sterol-regulated transcription of HMGR and other lipogenic genes is controlled by sterol regulatory element binding proteins (SREBPs). These membrane-bound transcription factors are escorted by SREBP cleavage activating protein (SCAP) from the endoplasmic reticulum (ER) to the Golgi apparatus where SREBPs are proteolytically processed to their active forms. In cultured cells, feedback inhibition of SREBP processing is mediated by Insigs. When sterols accumulate, Insigs block SREBP activation by retaining SCAP in the ER. Insigs also mediate rapid, sterol-dependent turnover of HMGR protein. When sterols accumulate, Insigs bind to HMGR and stimulate its ubiquitination and degradation. Although Insigs are key regulators of cholesterol homeostasis in cultured cells, their role in the intact mammal was undefined. To explore this question, gain-of-function and loss-of-function analyses were performed by studying the livers of genetically engineered mice. First, transgenic mice that overexpress Insig-1 in liver (TgInsig-1) were generated. In the livers of TgInsig-1 mice, nuclear SREBPs (nSREBPs) were reduced and SREBP processing was supersensitive to inhibition by feeding high-cholesterol diets. The block in SREBP processing reduced the mRNA levels of SREBP target genes. Levels of HMGR protein were reduced and declined further with cholesterol feeding. Next, knockout mice that lack Insig-1, Insig-2, or both Insigs were generated. In the livers of Insig double knockout mice, cholesterol and triglycerides accumulated to high levels, and despite their accumulation, nSREBPs and mRNAs of SREBP target genes were not suppressed. SREBP processing was insensitive to inhibition by feeding high-cholesterol diets. HMGR protein levels were increased and failed to decline with cholesterol feeding. As a consequence of Insig overexpression or deficiency and the respective effect on SREBPs and HMGR, hepatic cholesterol and fatty acid synthesis in living animals was decreased in TgInsig-1 mice and increased in Insig double knockout mice. These studies indicate that Insigs are essential regulators of hepatic lipid synthesis.Item Lipid utilization in the reproductive effort of female Kinosternon flavescens(Texas Tech University, 1983-05) Long, David RobertKinosternon flavescens maintains the highest lipid index of all reported turtles. Juveniles had larger lipid stores than females during most of the activity period. Chelonian lipid reserves show annual variation with egg development constituting a primary demand for stored lipids. Lipid incorporation in ovarian follicles occurred at a constant rate and at direct expense of the female's lipid reserve. The mean lipid index of oviducal eggs was higher than that reported for other chelonians. No correlation was evident between the lipid index of females and that of their oviducal eggs. Individual egg mass and clutch size increased with size of the female. The lipid index of oviducal eggs increased with clutch size.Item Lipids in respiratory particles of the Ergot fungus (Claviceps purpurea)(Texas Tech University, 1963-08) Sun, Frank FengkangNot availableItem Mitochondrial uncoupling links lipid catabolism to Akt inhibition and blockade of skin tumorigenesis(2014-08) Nowinski, Sara Marie; Mills, Edward MichaelIn order to support rampant cell growth, tumor cells must reprogram metabolism to simultaneously drive macromolecular biosynthesis and energy production. Mitochondrial uncoupling proteins (UCPs) oppose this phenotype by inducing futile mitochondrial respiration that is disengaged from ATP synthesis. We found that uncoupling protein 3 (UCP3) was normally expressed in follicular and epidermal keratinocytes and that its levels were augmented by calcium-induced differentiation in vitro. Over-expression of a UCP3 transgene targeted to the basal epidermis by the keratin-5 promoter (K5-UCP3) led to increased differentiation of both epidermal and bulge stem cells, the progenitors of most squamous carcinomas. Consistent with this phenotype, K5-UCP3 mice were completely protected from chemically induced skin carcinogenesis. To define the mechanisms by which UCP3 conferred such strong tumor resistance, we interbred K5-UCP3 mice with a “pre-initiated” mouse model, and found that UCP3 over-expression blocked tumor promotion. Uncoupled epidermis displayed reduced proliferation after treatment with tumor promoter, along with diminished activation of Akt signaling. This effect corresponded to decreased Akt activation by epidermal growth factor (EGF) in K5-UCP3 cells, along with UCP3 overexpressing primary human keratinocytes. Mechanistic studies revealed that uncoupling drove global lipid catabolism, along with impaired recruitment of Akt to the plasma membrane. Over-expression of wild type Akt rescued tumor promoter-induced proliferation and two-stage chemical carcinogenesis in bi-transgenic mice. Collectively, these findings demonstrate that mitochondrial uncoupling is an effective strategy to limit cell proliferation and tumorigenesis through inhibition of Akt, and suggest a novel mechanism of crosstalk between mitochondrial metabolism and growth signaling.Item Quantifying the Effect of Dietary Fats on the Enzyme Metabolizing Chemical Carcinogen 2-Acetylaminofluorene(Texas Tech University, 1978-05) Fann, Daw-YunnNot Available.Item SCAP, Insig, and Cholesterol Interactions in Mammalian Cells(2007-05-22) Feramisco, Jamison Derek; Brown, Michael S.Cholesterol synthesis in mammalian cells is highly regulated by an end-product feedback mechanism. The transcription of genes necessary for both fatty acid and cholesterol production are controlled by sterol regulatory element binding proteins (SREBPs). The critical regulatory step is the proteolytic release of SREBPs from their inactive membrane bound form. Soon after translation, SREBPs bind SREBP cleavage activating protein (SCAP), a polytopic membrane protein of the endoplasmic reticulum (ER). In sterol depleted situations, SCAP escorts SREBPs to the Golgi, where SREBPs are cleaved and can move freely to the nucleus and activate the numerous enzymes of cellular lipid homeostasis. When cellular sterol levels rise, the SCAP/SREBP complex binds to an ER resident protein named Insig. Upon binding to Insig, the movement of the SCAP/SREBP complex to the Golgi is inhibited, thus halting cholesterol and fatty acid synthesis. The mechanism by which the cell senses sterol levels has been long unknown. Radhakrishnan et al. and Adams et al. demonstrated that SCAP itself binds cholesterol and thus may act directly to sense cellular sterol levels and mediate the end-product feedback control of SREBPs. The goal of this thesis is to elucidate the molecular details of the interactions between SCAP, Insig and cholesterol. My thesis experimentally details the membrane topology of human Insig-1 and shows that it is a polytopic integral membrane protein of the ER with six transmembrane spanning segments. In addition, the amino and carboxy-termini of Insig are both facing the cytosol. Furthermore, crucial residues of Insig that are important for SCAP interaction are identified. My thesis has also defined distinct amino acids of SCAP that are essential for its role as a protein that binds Insig and as a protein that has the ability to bind cholesterol. An aspartic acid in the middle of transmembrane six is necessary for sterol regulated binding to Inisg, while residues in transmembrane segments one and three of SCAP are crucial for cholesterol binding both in vivo and in vitro.Item Storage stability of frozen mechanically separated beef(Texas Tech University, 1983-08) Lee, Chai-fenNot availableItem Structural studies with affinity-purified muscle and neuronal nicotinic acetylcholine receptors(Texas Tech University, 2007-05) Hamouda, Ayman K.; Blanton, Michael P.; Lombardini, J. Barry; Popp, R. Lisa; Pressley, Thomas A.; Machu, Tina K.Nicotinic acetylcholine receptors (nAChRs) are a heterogeneous group of ligand gated ion channels that mediate the function of the endogenous neurotransmitter acetylcholine. A more refined understanding of the molecular structure of individual neuronal nAChRs is a prerequisite for the development of subtype-selective ligands. Such ligands will be valuable in the understanding and treatment of certain CNS diseases as well as nicotine addiction. Using an acetylcholine derivatized affinity column originally used for purification of Torpedo nAChR, we have purified a4b2 and a4b4 neuronal nAChRs from HEK293 cell lines that stably express a4b2 or a4b4 nAChRs respectively. The lipid-protein interface and the agonist-binding site of purified neuronal nAChRs were directly examined using photoaffinity labeling with [125I]TID and [125I]Epibatidine respectively. The preliminary results of these studies include: 1) [125I]TID photoincorporates into the M4 and M1 transmembrane segments of both a4 and b2 subunits; 2) Within a4M4/b2M4 segments, [125I]TID labeled amino acid residues a4Cys582/b2Cys445 which are identical (in the aligned sequence) to the [125I]TID-labeled residues Cys418 in the lipid exposed face of Torpedo a1M4; 3) [125I]TID also labeled a4Arg572 within a4M4 which is situated in the same position as His408 in the lipid exposed face of Torpedo a1M4; 4) Within a4M1 segment, [125I]TID labeled Cys226, Cys231 and Leu232 which correspond to [125I]TID labeled residues Cys222, Phe227 and Leu228 in the lipid exposed face of Torpedo a1M1. In similar fashion, [125I]TID labeled b2Cys220 and b2Val221 which correspond to [125I]TID labeled Cys222 and Leu223 in the lipid exposed face of Torpedo a1M1. 5) Further studies are needed to determine if [125I]TID photoincorporates into the M2 and M3 transmembrane segments; 6) Photoaffinity labeling of a4b2 and a4b4 nAChRs with [125I]Epibatidine reveals that [125I]Epibatidine photoincorporates specifically into the b4 subunit with no (or insignificant photoincorporation) within a4 and b2 subunits; 7) [125I]Epibatidine photoincorporation ion the a4 subunit was limited to the agonist binding pocket as the majority of labeling was displaceable by addition of nicotine; 8) The site of specific [125I]Epibatidine photincorporation within the b4 subunit was mapped to loop E (b4Val102-Glu131) within the complementary components of the agonist binding site.Item Tandem mass spectrometry approaches to characterizing challenging biomolecules : stapled and cyclic peptides and variants of lipid A from gram-negative bacteria(2016-08) Crittenden, Christopher Martin; Brodbelt, Jennifer S.; Mullins, Charles BMass spectrometry has emerged as a leading tool in the field of chemistry as an analytical method for the characterization of small molecules, proteins, and other complex biomolecules. Specifically, cyclic and stapled peptides have become an intriguing class of biomolecules in drug research afforded to them because of their biological stability and resistance to proteolytic digestions. However, challenges are presented in regards to the characterization of these molecules as traditional methods are ineffective in determining a ring-opening site on the peptidic backbone. Additionally, lipid A, the hydrophobic domain of lipopolysaccharide (LPS), consists of a diglucosamine backbone and is responsible for fastening LPS to a membrane surface. Lipid A becomes a biologically relevant molecule to study as its function within LPS is directly related to the infectious and toxic properties of gram-negative bacteria, but the molecule is structurally complex and offers many challenges in terms of traditional mass spectrometry characterization. Presented in the thesis are methods to further comprehend structural motifs related to the aforementioned biomolecules. The “ornithine effect”, which describes the conversion of an arginine residue to an ornithine residue via reaction with hydrazine and subsequent preferential cyclization via nucleophilic attack of the ornithine side-chain to the neighboring carbonyl group, inducing heterolytic cleavage of the adjacent amide bond under gentle activation, is used to preferentially open cyclic and stapled rings to linearize these challenging biomolecules. Ramped collisional and photon based activation (in terms of energy and laser pulses) of lipid A molecules that contain differences in acyl-chain length and connectivity reveal general trends about the lability of certain bonds on the lipid A molecules themselves and paints a picture of the overall fragmentation trends associated with variations in lipid A structural motifs.Item The effect of dietary lipid on the metabolism of ethanol(Texas Tech University, 1978-05) Brigman, Amanda LeeNot availableItem The effect of resistance, endurance, and combination exercise on lipid metabolism and non-traditional cardiovascular disease risk markers in previously untrained men(2009-05-15) Martin, Steven EdwardWhile adhering to an active lifestyle has been associated with a more favorable lipid profile and reduced risk of coronary heart disease (CHD), information regarding the optimal training modality is not well defined. This project examined the acute and chronic effects of endurance (ET), resistance (RT), and combination endurance / resistance (CT) exercise on lipid metabolism and non-traditional CHD risk markers in untrained men. Thirty-one subjects were randomly assigned to participate for 12 weeks in one of three exercise groups: ET, RT, or CT. To measure the effects of acute exercise on lipid metabolism, fasting blood samples were obtained before (baseline) and 24 hours after (24 h) acute exercise (treadmill jogging at 70% V . O2peak, 350 kcals; weight lifting exercise at 70% of 1RM; combination of treadmill jogging and weight lifting at 70% maximal capacity, 350 kcals). Blood variables were adjusted for plasma volume shifts. This acute exercise protocol was completed on two different occasions corresponding to 0 and 12 weeks of training. For acute exercise (pre-training), significant results of a 3 (Group) x 2 (Time) ANOVA, repeated for Time, (p < 0.05) were as follows: TC, HDL-C, HDL2&3-C were lower 24 h after exercise in the RT group. HDL2-C was higher 24 h after exercise in the CT and ET groups. In the ET group, LDL1-C was elevated 24 h after exercise. With all groups combined, LDL3-C and the TC / HDL-C ratio were elevated and LDL2-C decreased 24 h after exercise. For exercise training, significant results of a 3 (Group) x 2 (Training Period) ANOVA, repeated for Training Period, (p < 0.05) were as follows: Body Fat, LDL2-C, and apo A-I were lower after training. Changes in other lipid variables were similar in untrained males performing different types of exercise training. For acute exercise (post-training), significant results of a 3 (Group) x 2 (Time) ANOVA, repeated for Time, (p < 0.05) were as follows: TC, HDL-C, HDL2-C, LDL-C, NONHDL-C, VLDL-C, IDL-C, LDL3-C, LDL density, and LPLa were all higher 24 h after exercise. Post-exercise changes in the dependent variables were similar in trained males performing different types of exercise.Item Tracing organic matter pathways in marine food webs using fatty acids and compound specific stable isotope analysis(2015-08) Smith, Stephanie Denise; McClelland, James W.; Dunton, Kenneth H; Walther, Benjamin DOrganic matter inputs to the marine environment vary over seasonal and spatial scales, altering the type and availability of food sources for marine consumers. It is important to identify diet in order to understand basic ecology, characterize trophic interactions, and predict consequences of biotic and abiotic change within a community. Methods of direct observation of diet and feeding can be difficult, so indirect methods have been developed such as analysis of gut contents and fecal pellets. However, these methods only represent a snapshot of the last meal, and provide information about what was ingested, but not what was actually incorporated into consumer tissues. Therefore, biogeochemical approaches such as fatty acid (FA) and stable isotope analyses have been developed, which provide a time-integrated measure of diet. Further, stable isotope measurements of specific FA markers can be used to identify carbon sources, and can be applied to a variety of food web studies (Iverson et al., 2004). The purpose of this research is to examine the linkages between organic carbon sources and trophic transfer by consumers. To achieve this, we use FA biomarkers and compound specific stable isotope analysis (CSIA) to trace carbon cycling. This study has two main components: environmental sampling and experimental research. Chapter 1 demonstrates the use of these tools for elucidating seasonal trophic linkages in invertebrates collected from the Alaskan Arctic coast. Overall, invertebrate diets were characterized by terrestrial, detrital, and carnivorous sources in winter and spring, with a shift toward autochthonous diatom-based diets in summer. Our results demonstrate the importance of terrestrial organic carbon as a subsistence food source in winter, whereas in situ production in summer was critical for accumulating FA stores rich in essential FAs. Chapter 2 is an experimental feeding study designed to quantify the incorporation rates of 18:2n-6 from diet to tissue in Atlantic croaker. Liver tissues accumulated FAs more quickly than muscle tissues, but both tissues reached equilibrium at 5 to 7 weeks. From these experiments, quantitative assessments of diet sources can be made with confidence when using FAs to understand trophic interactions of Atlantic croaker and other similar species.