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Paramecium, a unicellular ciliate, can be attracted by various chemical stimuli. Chemoattractants such as glutamate, folate, cAMP, and acetate activate different receptor mediated signal transduction pathways. The final event in these signal transductions is a hyperpolarization of membrane potential, which makes Paramecium swim smoothly and fast. There is evidence that the effecter of this hyperpolarization is the plasma membrane calcium ATPase (PMCA), that when activated, expels Ca2+ from the cell. In Paramecium three PMCA isoforms, named PMCA2, 3, and 4, have been cloned. PMCA2 is associated with lipid rafts, which is demonstrated by its resistance to cold detergent solubilization and distribution in sucrose density gradients in ultracentrifugation. PMCA3 and 4 are not associated with lipid rafts. On the cell surface, PMCAs are localized to the bases of cilia. Sterol-depletion by methyl-ß-cyclodextrin (MßCD) treatment disrupts the distribution of PMCA2 in sucrose density gradients and ciliary base-localization on the cell surface. MßCD treatment also decreases the chemoattraction to glutamate and cAMP. This indicates that PMCA2 and its association with lipid rafts are essential in the chemoattraction signal transduction pathways. Based on these results, a model of membrane domains incorporating three signal transduction pathways is proposed.

Paramecium, a ciliate, is an important model for studying Ca2+ signaling and understanding chemoreception and signal transduction. There are several proteins, such as plasma membrane calcium ATPases (PMCAs)/ calcium pumps, SERCA pumps, calmodulin and Ca2+ channels that play an important role in maintaining intracellular Ca2+ level and signaling in Paramecium. Isoform 2 of PMCA has been identified in both the cilia and pellicle membranes of Paramecium, the activity of which leads to hyperpolarization. Plasma and ciliary membrane of Paramecium is made up of a variety of sterols and sphingolipids which constitute lipid rafts, demonstrated by the presence of detergent resistant membranes and their distribution in sucrose and Optiprep density gradients. PMCAs are important markers of lipid rafts and PMCA 2 is found to be localized in lipid rafts of both the cilia and somatic membrane of Paramecium. Methyl-β-cyclodextrin treatment can remove up to 42% of sterols from pellicle membranes but only about 12% from cilia. Sterol depletion of pellicle perturbs the distribution of PMCA 2 and other raft proteins in pellicle which is not observed in cilia as evident from western blot analysis and immunomicroscopic studies. There is evidence that selection of gradient medium for study of lipid rafts and its associated proteins is very important in Paramecium. Glutamate receptors and adenylyl cyclase, the upstream molecules of the signal transduction pathway through PMCA have also been identified in cellular cilia, indicating that these raft molecules forms a platform for signaling in Paramecium cilia.

Thesis (Ph. D.)--Ohio State University, 2006. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2007 Sep 11

Meat lipid oxidation causes negative quality effects, especially in further processed products. Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and rosemary extract (RM) are common antioxidants, but plant-based tannin compounds have been shown to be effective antioxidants. The objective was to evaluate antioxidant effectiveness, pH, color, and sensory effects of several tannin sources. In study 1, 19 percent fat ground beef was mixed with no treatment (control), BHA/BHT (0.02percent), RM (0.2percent), or 0.25percent or 0.5percent powders of Chardonnay grapeseed (CG), Norton grapeseed (NG), CitruSmart (CS), or dried cherry (CP). Raw and cooked patties were aerobically stored for 0 to 5 days at 4 degrees C. Cooked patties were analyzed using the TBARS (thiobarbituric acid reactive substances) method. Raw patties were analyzed for pH, instrumental color, subjective color, and ingredient specks. Study 2 was similar, except the treatments were 0.25percent and 0.5percent powders of CG, chestnut (CN), mimosa (M), and quebracho (Q) tannins, as well as 0.5percent NG, 0.02percent BHA/BHT, 0.2percent RM, and a control. In study 1, only the NG and CG pre-cooked patties had similar or lower TBARS values compared to RM and BHA/BHT patties. All tannin treatments, except 0.25percent CG and 0.25percent CS, lowered pH compared to the control. Patties with NG and 0.5percent CG were darker, and tannin-treated patties were not redder than the control. Patties with CG and 0.5percent NG were less yellow. Subjectively, tannin-treated patties did not have less discoloration during storage, and the CG and NG patties had numerous visible ingredient specks. In study 2, CN, M, Q, and 0.5percent CG treated patties had low TBARS during storage. pH was slightly lower in CG and CN patties than the control. All tannin-treated patties were darker than the control patties, except patties containing 0.25percent CG and Q, and control patties had the highest red values. Tannin-treatments patties, except CN and Q patties, were less yellow. Subjectively, only 0.25percent M patties had less discoloration than control patties, while 0.5percent CN patties were more discolored. Norton and Chardonnay grapeseed flour and chesnut, mimosa, and quebracho powders would be recommended for pre-cooked ground beef patties based on their antioxidant effectiveness in these studies.