Niacin is a widely used lipid-regulating agent in dyslipidemic patients. Previously, we have shown that niacin inhibits triacylglycerol synthesis. In this report, using HepG2 cells, we have examined the effect of niacin on the mRNA expression and microsomal activity of diacylglycerol acyltransferase 1 and 2 (DGAT1 and DGAT2), the last committed but distinctly different enzymes for triglyceride synthesis. Addition of niacin to the DGAT assay reaction mixture dose-dependently (0-3 mM) inhibited DGAT activity by 35-50%, and the IC 50 was found to be 0.1 mM. Enzyme kinetic studies showed apparent K m values of 8.3 M and 100 M using [ 14 C]oleoyl-CoA and sn -1,2-dioleoylglycerol as substrates, respectively. A decrease in apparent V max was observed with niacin, whereas the apparent K m remained constant. A Lineweaver-Burk plot of DGAT inhibition by niacin showed a noncompetitive type of inhibition. Niacin selectively inhibited DGAT2 but not DGAT1 activity. Niacin inhibited overt DGAT activity. Niacin had no effect on the expression of DGAT1 and DGAT2 mRNA. These data suggest that niacin directly and noncompetitively inhibits DGAT2 but not DGAT1, resulting in decreased triglyceride synthesis and hepatic atherogenic lipoprotein secretion, thus indicating a major target site for its mechanism of action. Niacin is an effective, unique lipid-regulating agent that beneficially reduces plasma triglycerides (TGs), cholesterol, and atherogenic apolipoprotein B (apoB)-containing lipoproteins (VLDL, LDL, and lipoprotein [a]) and increases antiatherogenic apoA-I-containing HDL levels (1-3). Several clinical trials have demonstrated that treatment with niacin significantly reduces total mortality and coronary events and retards the progression or induces the regression of coronary atherosclerosis (4-6). Despite its wide usage as a broad-spectrum lipid-regulating agent, the cellular and molecular mechanisms by which niacin modulates the hepatic lipid metabolism and the production of VLDL and LDL particles are incompletely understood.Using HepG2 cells as an in vitro model system, we have previously shown that niacin inhibited the incorporation of radiolabeled oleic acid or glycerol into TGs, suggesting decreased de novo synthesis of TGs by niacin (7). Additionally, we have shown that niacin also increased intracellular apoB degradation in HepG2 cells (7). Because the synthesis and availability of TG play a critical role in intracellular apoB processing and secretion of apoB-containing lipoproteins (8-10), our previous studies suggested that niacin, by inhibiting TG synthesis, increased intracellular apoB degradation, resulting in reduced secretion of apoB-containing particles (7). In support of these in vitro studies, earlier turnover studies in humans suggested that niacin decreased the production (transport) rate of TG from radiolabeled fatty acids, thus decreasing TG-rich lipoproteins (e.g., VLDL) and their product LDL (11).Modulation in the TG synthetic pathway and associated key enzyme systems may provide important to...

The signal transduction and molecular mechanisms underlying a-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-mediated neuroprotection are unknown. In the present study, we determined a major AMPA receptor-mediated neuroprotective pathway. Exposure of cerebellar granule cells to AMPA (500 lM) + aniracetam (1 lM), a known blocker of AMPA receptor desensitization, evoked an accumulation of brain-derived neurotropic factor (BDNF) in the culture medium and enhanced TrkB-tyrosine phosphorylation following the release of BDNF. AMPA also activated the src-family tyrosine kinase, Lyn, and the downstream target of the phosphatidylinositol 3-kinase (PI3-K) pathway, Akt. Extracellular signal regulated kinase (ERK), a component of the mitogen-activated protein kinase (MAPK) pathway, was also activated. K252a, a selective inhibitor of neurotrophin signaling, blocked the AMPA-mediated neuroprotection. The involvement of BDNF release in protecting neurons by AMPA was confirmed using a BDNF-blocking antibody. AMPA-mediated neuroprotection is blocked by PP1, an inhibitor of src family kinases, LY294002, a PI3-K inhibitor, or U0126, a MAPK kinase (MEK) inhibitor. Neuroprotective concentrations of AMPA increased BDNF mRNA levels that was blocked by the AMPA receptor antagonist, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX). The increase in BDNF gene expression appeared to be the downstream target of the PI3-K-dependent activation of the MAPK cascade since MEK or the PI3-K inhibitor blocked the AMPA receptor-mediated increase in BDNF mRNA. Thus, AMPA receptors protect neurons through a mechanism involving BDNF release, TrkB receptor activation, and a signaling pathway involving a PI3-K dependent activation of MAPK that increases BDNF expression. Keywords: Akt, AMPA, aniracetam, BDNF, ERK1/ 2, neuroprotection. J. Neurochem. (2004) 90, 807-818. Glutamate is the major excitatory neurotransmitter in the mammalian CNS and acts through two types of receptors, ionotropic and metabotropic (Hollman et al. 1989;Schoepp et al. 1999). Glutamate has also been implicated in the pathophysiology of hypoxic/ischemic neuronal damage (Olney et al. 1971;Choi 1995). The ionotropic glutamate receptor subtypes, N-methyl-D-aspartate (NMDA) (Choi 1995) and a-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors are thought to play a major role in the pathophysiology of hypoxic-ischemic neuronal damage

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Genome rearrangement is an important area in computational biology and bioinformatics. The translocation operation is one of the popular operations for genome rearrangement. It was proved that computing the unsigned translocation distance is NP-hard. In this paper, we present a (1.5 + epsilon)-approximation algorithm for computing unsigned translocation distance which improves upon the best known 1.75-ratio. The running time of our algorithm is O(n2 + (4/epsilon)1.5 square root log(4/epsilon )2(4/epsilon), where n is the total number of genes in the genome.

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In this paper we report our efforts to enhance the immunogenicity of Pfs28, a transmission blocking vaccine candidate of Plasmodium falciparum, using a strategy of chemical conjugation. With an improved procedure Pfs28 was covalently coupled to the mutant and nontoxic ExoProtein A of Pseudomonas aeruginosa by the reaction between thiolated antigen and maleimide modified carrier protein. The optimized process resulted in a higher antigen-carrier conjugation ratio, and the conjugation product could be purified using single-step size-exclusion chromatography. A significant increase in immunogenicity measured by ELISA was observed in mice immunized with conjugated Pfs28 as compared to unconjugated Pfs28.

We applied a transdimensional stochastic inversion algorithm, reversible jump Markov chain Monte Carlo (rjMCMC), to angle-stack seismic inversion for characterization of reservoir acoustic and shear impedance with uncertainty quantification. The rjMCMC is able to infer the number of parameters for the model as well as the parameter values. In our case, the number of parameters depends on the number of model layers for a given data set. We also use this method in uncertainty quantification because a transdimensional sampling helps prevent underparameterization or strong overparameterization. An ensemble of models with proper parameterization can improve parameter estimation and uncertainty quantification. Our new results in uncertainty analysis indicate that (1) the uncertainty in seismic inversion, including uncertainty in earth properties and their locations, is related to the discontinuity of property across an interface, and (2) there is a trade-off between property uncertainty and location uncertainty. A stronger discontinuity will induce more property uncertainty but less location uncertainty at the discontinuity interface. Therefore, we further use the inversion uncertainty as a novel seismic attribute to assist in delineation of subsurface discontinuity interfaces and quantify the magnitude of the discontinuities, which further facilitates quantitative interpretation and stratigraphic interpretation.

Plasmodium falciparum apical membrane antigen 1 (AMA1) is an asexual blood-stage vaccine candidate against the malaria parasite. AMA1-C1/ISA720 refers to a mixture of recombinant AMA1 proteins representing the FVO and 3D7 alleles in 1:1 mass ratio, formulated with Montanide® ISA 720 as a water-in oil emulsion. In order to develop the AMA1-C1/ISA720 vaccine for human use, it was important to determine the shelf life of this formulation. Previously it was found 267mM glycine stabilized the proteins in Montanide® ISA 720 formulations for a short period of time at 2-8°C[25], we now test the long term stability of AMA1-C1 at 10 and 40 μg/ml formulated with Montanide® ISA 720 with 50 mM glycine as a stabilizer. Stability of AMA1-C1/ISA720 at different time points following formulation (0, 5, 12 or 18 months) was evaluated by determining the mean particle size (diameter of the mean droplet volume), total protein content by a Modified Lowry assay, identity and integrity using western blot and SDS-PAGE. Our results showed that the mean particle size of these emulsions increased over time, whereas protein content, as determined by an ELISA method using a monoclonal antibody against penta-his, decreased over time. For the 10 μg/ml AMA1-C1/ISA720 vaccine, the protein content with was 6.5 ± 2.2 μg/ml, and for the 40 μg/ml AMA1-C1/ISA720 vaccine, the protein content was only 8.2 ± 2.3 μg/ml after 18 months of storage at 2-8°C. These results suggest that the integrity of the protein was affected by long-term storage. The results of the present study indicate that the AMA1-C1/ISA720 emulsion was unstable after 12 months of storage, after which AMA1-C1 proteins were partially degraded.