Gale M. Strasburg

Structure-activity relationships for antioxidant activities of a series of flavonoids in a liposomal system.

Structurally diverse plant phenolics were examined for their abilities to inhibit lipid peroxidation induced either by Fe(II) and Fe(III) metal ions or by azo-derived peroxyl radicals in a liposomal membrane system. The antioxidant abilities of flavonoids were compared with those of coumarin and tert-butylhydroquinone (TBHQ). The antioxidant efficacies of these compounds were evaluated on the basis of their abilities to inhibit the fluorescence intensity decay of an extrinsic probe, 3-(p-(6-phenyl)-I,3,5-hexatrienyl)phenylpropionic acid (DPH-PA), caused by the free radicals generated during lipid peroxidation. All the flavonoids tested exhibited higher antioxidant efficacies against metal-ion-induced peroxidations than peroxyl-radical-induced peroxidation, suggesting that metal chelation may play a larger role in determining the antioxidant activities of these compounds than has previously been believed. Distinct structure-activity relationships were also revealed for the antioxidant abilities of the flavonoids. Presence of hydroxyl substituents on the flavonoid nucleus enhanced activity, whereas substitution by methoxy groups diminished antioxidant activity. Substitution patterns on the B-ring especially affected antioxidant potencies of the flavonoids. In cases where the B-ring could not contribute to the antioxidant activities of flavonoids, hydroxyl substituents in an catechol structure on the A-ring were able to compensate and become a larger determinant of flavonoid antioxidant activity.

Antioxidant and cyclooxygenase inhibitory phenolic compounds from Ocimum sanctum Linn.

Anti-oxidant bioassay-directed extraction of the fresh leaves and stems of Ocimum sanctum and purification of the extract yielded the following compounds; cirsilineol [1], cirsimaritin [2], isothymusin [3], isothymonin [4], apigenin [5], rosmarinic acid [6], and appreciable quantities of eugenol. The structures of compounds 1-6 were established using spectroscopic methods. Compounds 1 and 5 were isolated previously from O. sanctum whereas compounds 2 and 3 are here identified for the first time from O. sanctum. Eugenol, a major component of the volatile oil, and compounds 1, 3, 4, and 6 demonstrated good antioxidant activity at 10-microM concentrations. Anti-inflammatory activity or cyclooxygenase inhibitory activity of these compounds were observed. Eugenol demonstrated 97% cyclooxygenase-1 inhibitory activity when assayed at 1000-microM concentrations. Compounds 1, 2, and 4-6 displayed 37, 50, 37, 65, and 58% cyclooxygenase-1 inhibitory activity, respectively, when assayed at 1000-microM concentrations. Eugenol and compounds 1, 2, 5, and 6 demonstrated cyclooxygenase-2 inhibitory activity at slightly higher levels when assayed at 1000-microM concentrations. The activities of compounds 1-6 were comparable to ibuprofen, naproxen, and aspirin at 10-, 10-, and 1000-microM concentrations, respectively. These results support traditional uses of O. sanctum and identify the compounds responsible.

Theory and applications of fluorescence spectroscopy in food research

Abstract Fluorescence spectroscopy is a rapid, sensitive method for characterizing molecular environments and events. In spite of its utility, food researchers have been slow to adopt fluorescence methodology, partly because its value has gone unrecognized. This article presents a brief overview of the theory of fluorescence spectroscopy, together with some examples of applications of this technique to illustrate its potential for addressing key problems in food science.

Pale, soft, exudative turkey—The role of ryanodine receptor variation in meat quality

The poultry industry has made significant advances in growth rate, feed efficiency, and breast muscle yield through intensive breeding of turkeys. However, a meat quality problem known as pale, soft, exudative (PSE) meat presents the industry with a major challenge during periods of stress, such as the onset of a prolonged heat wave. The biochemical characteristics of PSE turkey are strikingly similar to those of PSE pork. Abnormally rapid postmortem metabolism, stimulated in part by high concentrations of calcium ions, may be one of the underlying factors associated with the incidence of PSE turkey. This presentation summarizes our studies on the avian ryanodine receptors and suggests that heat stress may alter the expression pattern of splice variants of ryanodine receptors, which, in turn, could affect postmortem calcium homeostasis.

Oxidation of the skeletal muscle Ca2+ release channel alters calmodulin binding

This study presents evidence for a close relationship between the oxidation state of the skeletal muscle Ca2+ release channel (RyR1) and its ability to bind calmodulin (CaM). CaM enhances the activity of RyR1 in low Ca2+ and inhibits its activity in high Ca2+. Oxidation, which activates the channel, blocks the binding of125I-labeled CaM at both micromolar and nanomolar Ca2+concentrations. Conversely, bound CaM slows oxidation-induced cross-linking between subunits of the RyR1 tetramer. Alkylation of hyperreactive sulfhydryls (<3% of the total sulfhydryls) on RyR1 with N-ethylmaleimide completely blocks oxidant-induced intersubunit cross-linking and inhibits Ca2+-free125I-CaM but not Ca2+/125I-CaM binding. These studies suggest that 1) the sites on RyR1 for binding apocalmodulin have features distinct from those of the Ca2+/CaM site, 2) oxidation may alter the activity of RyR1 in part by altering its interaction with CaM, and 3) CaM may protect RyR1 from oxidative modifications during periods of oxidative stress.

The effect of heat stress on thyroid hormone response and meat quality in turkeys of two genetic lines

The current study evaluated the effect of heat stress on thyroid hormone (T(3) and T(4)) response and meat quality traits in two turkey lines: a growth-selected commercial line and a genetically unimproved control line. Birds were subjected to heat stress for different durations before harvest. Commercial line had higher pH(15min), and lightness values, but lower cook loss and marinade uptake than control line during the heat stress. There was no difference in drip loss between the two lines. The T(3) concentration was positively correlated with cook loss and was negatively correlated with marinade uptake. The thyroid hormone response during heat stress was less stable in the commercial line than in the control line and the unstable thyroid hormone response in commercial turkeys caused by heat exposure might influence the consistency of meat quality. Results of this study may provide an application in selecting turkeys which yield consistent meat quality.

Inhibition of heterocyclic aromatic amine formation in fried ground beef patties by garlic and selected garlic-related sulfur compounds

The effects of garlic and selected organosulfur compounds (diallyl disulfide, dipropyl disulfide, diallyl sulfide, allyl methyl sulfide, allyl mercaptan, cysteine, and cystine) on the formation of heterocyclic aromatic amines (HAAs) in fried ground beef patties were evaluated. Minced garlic cloves (ca. 4.8 to 16.7%, wt/wt) or organosulfur compounds (0.67 mmol) were added directly to ground beef. Patties (100 g) were fried at 225 degrees C (surface temperature) for 10 min per side. Two patties were fried for each replication, and five replicates were analyzed for each treatment. For each replicate, four subsamples were analyzed (two unspiked subsamples for concentration and two spiked subsamples for the recovery of HAA standards). The volatile sulfur compounds significantly (P < 0.05) reduced concentrations of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine by reductions of 46 to 81%, while average reductions of 35, 22, and 71%, were achieved with cystine, cysteine, and whole garlic, respectively. The volatile sulfur compounds reduced concentrations of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline by 34 to 67%, while reductions of 25, 19, and 63% (P < 0.05) were achieved with cystine, cysteine, and whole garlic, respectively. These studies confirm that garlic and some organosulfur compounds have the potential to reduce HAA formation incooked beef patties.

Transcriptional profiling identifies differentially expressed genes in developing turkey skeletal muscle

BackgroundSkeletal muscle growth and development from embryo to adult consists of a series of carefully regulated changes in gene expression. Understanding these developmental changes in agriculturally important species is essential to the production of high quality meat products. For example, consumer demand for lean, inexpensive meat products has driven the turkey industry to unprecedented production through intensive genetic selection. However, achievements of increased body weight and muscle mass have been countered by an increased incidence of myopathies and meat quality defects. In a previous study, we developed and validated a turkey skeletal muscle-specific microarray as a tool for functional genomics studies. The goals of the current study were to utilize this microarray to elucidate functional pathways of genes responsible for key events in turkey skeletal muscle development and to compare differences in gene expression between two genetic lines of turkeys. To achieve these goals, skeletal muscle samples were collected at three critical stages in muscle development: 18d embryo (hyperplasia), 1d post-hatch (shift from myoblast-mediated growth to satellite cell-modulated growth by hypertrophy), and 16wk (market age) from two genetic lines: a randombred control line (RBC2) maintained without selection pressure, and a line (F) selected from the RBC2 line for increased 16wk body weight. Array hybridizations were performed in two experiments: Experiment 1 directly compared the developmental stages within genetic line, while Experiment 2 directly compared the two lines within each developmental stage.ResultsA total of 3474 genes were differentially expressed (false discovery rate; FDR < 0.001) by overall effect of development, while 16 genes were differentially expressed (FDR < 0.10) by overall effect of genetic line. Ingenuity Pathways Analysis was used to group annotated genes into networks, functions, and canonical pathways. The expression of 28 genes involved in extracellular matrix regulation, cell death/apoptosis, and calcium signaling/muscle function, as well as genes with miscellaneous function was confirmed by qPCR.ConclusionsThe current study identified gene pathways and uncovered novel genes important in turkey muscle growth and development. Future experiments will focus further on several of these candidate genes and the expression and mechanism of action of their protein products.

Differential gene expression between normal and pale, soft, and exudative turkey meat

In response to high consumer demand, turkeys have been intensively selected for rapid growth rate and breast muscle mass and conformation. The success in breeding selection has coincided with an increasing incidence of pale, soft, and exudative (PSE) meat defect, especially in response to heat stress. We hypothesized that the underlying mechanism responsible for the development of PSE meat arises from differences in expression of several critical genes. The objective of this study was to determine differential gene expression between normal and PSE turkey meat using a 6K turkey skeletal muscle long oligonucleotide microarray. Breast meat samples were collected from Randombred Control Line 2 turkeys at 22 wk of age, and classified as normal or PSE primarily based on marinade uptake (high = normal, low = PSE). Total RNA was isolated from meat samples with the highest (normal, n = 6) and the lowest (PSE, n = 6) marinade uptake. Microarray data confirmation was conducted using quantitative real-time PCR. Selection of differentially expressed genes for pathway analysis was performed using a combination of fold change (FC) ranking (FC < -1.66, FC >1.66) and false discovery rate (<0.35) as criteria. The calcium signaling pathway was highlighted as the top canonical pathway associated with differential gene expression between normal and PSE turkey. Dramatic downregulation of fast-twitch myosin heavy chain coupled with upregulation of slow-twitch myosin and troponin C suggested a switch of skeletal muscle isoforms, which may alter muscle fiber arrangement and formation of actin-myosin complexes. Changes in expression of genes in the actin cytoskeleton signaling pathway also suggest altered structures of actin filaments that may affect cell motility as well as strength and flexibility of muscle cells. Substantial downregulation of pyruvate dehydrogenase kinase, isozyme 4 was observed in PSE samples, suggesting altered regulation of the aerobic metabolic pathway in the birds that developed PSE meat defect.

Interaction of calmodulin with phospholamban and caldesmon : comparative studies by 1H-NMR spectroscopy

In order to identify comparative aspects of the interaction of calmodulin with its target proteins, proton magnetic-resonance studies of complex formation between calmodulin and defined segments of phospholamban and caldesmon have been undertaken. Residues 3-15 in the cytoplasmic region of phospholamban, an integral membrane protein of cardiac sarcoplasmic reticulum believed to regulate the calcium pumping ATPase, are shown to contribute to interaction with calmodulin. Using wheat germ calmodulin specifically modified with a spin-label to provide the spectral means for spatial localisation, these residues of phospholamban were correlated with binding in the vicinity of the probe attached to Cys-27 in the N-terminal domain of calmodulin. This interaction, relevant to the mechanism of calmodulin-dependent phosphorylation of phospholamban that relieves its inhibitory influence on the calcium pump, provides a useful model system for comparative study of the properties of calmodulin-binding domains. We contrast here a calmodulin-binding segment in the C-terminal region of caldesmon localised by 1H-NMR study of the interface(s) between the two proteins. These observations are discussed in the context of other calmodulin-binding sequences.