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Additive Interactions (additive + interaction)
Selected AbstractsAdditive interactions in the stabilization of film grade high-density polyethylene.JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2002Part I: Stabilization, influence of zinc stearate during melt processing The melt stabilization activity of some of the most commercially significant phenolic antioxidants and phosphites (alone and in combination), without and with zinc stearate, was studied in high-density polyethylene (HDPE) produced by Phillips catalyst technology. Multiple pass extrusion experiments were used to degrade the polymer melt progressively. The effect of stabilizers was assessed via melt flow rate (MFR) and yellowness index (YI) measurements conducted as a function of the number of passes. The level of the phenolic antioxidant remaining after each extrusion was determined by high-performance liquid chromatography (HPLC). Phenolic antioxidants and phosphites both improved the melt stability of the polymer in terms of elt viscosity retention; the influence of zinc stearate was found to be almost insignificant. However, phosphites and zinc stearate decreased the discoloration caused by the phenolic antioxidants. A correlation was found between the melt stabilization performance of phosphites and their hydroperoxide decomposition efficiency determind via a model hydroperoxide compound. Steric and electronic effects associated with the phosphorus atom influenced the reactivity towards hydroperoxides. Furthermore, high hydrolytic stability did not automatically result in lower efficiency. Besides phosphite molecular structure, stabilization activity was also influenced by the structure of the primary phenolic antioxidant and the presence of zinc stearate. [source] Pharmacodynamic interaction of recombinant human interleukin-10 and prednisolone using in vitro whole blood lymphocyte proliferationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2002Abhijit Chakraborty Abstract Prednisolone, a commonly used synthetic corticosteroid, and IL-10, a cytokine under investigation for strong antiinflammatory properties, are being contemplated as a potential joint therapeutic regimen in immune disorders. Their pharmacodynamic interactions were examined in blood from healthy adult male and female volunteers using an in vitro phytohemagglutinin (PHA)-stimulated whole,blood lymphocyte proliferation technique. Isobolograms along with parametric competitive and noncompetitive interaction models were used to determine the nature and intensity of interactions. Single drug effects show prednisolone more efficacious in inhibiting lymphocyte proliferation with an IC50 of 3.3 ng/mL and Imax value of 1, signifying complete suppression. Analogous parameters for IL-10 were 16.2 ng/mL for IC50 and 0.89 for Imax. There were no significant differences in the single drug immunosuppressive effects among genders. Their joint effects showed additive interaction based on isobolographic analysis. Parametric analysis using the competitive interaction model described their interaction as slightly synergistic, while the noncompetitive interaction modeling indicate a small degree of antagonism. Also, the joint effects in females tend to be more antagonistic than males. Concomitant use of prednisolone and IL-10 should thus reflect the net additive responses to concentrations of each agent. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:1334,1342, 2002 [source] Cytochrome P4501A induction potencies of polycyclic aromatic hydrocarbons in a fish hepatoma cell line: Demonstration of additive interactionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2000Karl Fent Abstract The relative CYP1A induction potencies, determined as ethoxyresorufin- O -deethylase (EROD) activity, and the cytotoxicities of 19 compounds with one to six benzene rings, mixtures of polycyclic aromatic hydrocarbons (PAHs), and contaminated landfill leachates have been determined in the permanent fish hepatoma cell line PLHC-1. No CYP1A induction was observed with benzene, naphthalene, anthracene, acenaphthene, benzo[g,h,i]perylene, and fluorene and low induction was found with fluoranthene and phenanthrene. All other PAHs with three and more benzene rings led to a concentration-related induction of CYP1A, with rebound decreases at high concentrations resulting in bell-shaped concentration,activity curves. Fish-related induction equivalency factors (IEFs) were estimated for all PAHs on the basis of EC50 values of their EROD activities and are reported here for the first time. The following order of decreasing IEFs was found: dibenz[a,h]anthracene > dibenzo[a,i]pyrene > benzo[k]fluoranthene > 3-methylcholanthrene > benzo[a]pyrene > benzo[e]pyrene > chrysene > 7,12-dimethylbenz[a]anthracene > perylene > benz[a]anthracene > pyrene. In contrast to the EROD activity, the immunodetectable protein content determined by ELISA showed a concentration-dependent increase. The interaction of PAHs in mixtures of up to eight individual compounds was additive based on their EROD activities. In landfill leachates, determined induction equivalents (IEQ) were significantly higher than calculated IEQs based on analytical measurements, which indicates additional unknown inducing compounds present in leachates. This study shows that the PLHC-1 cell in vitro system serves as an integrative bioanalytical tool in the ecotoxicological evaluation of aquatic environmental samples contaminated with CYP1A-inducing compounds. [source] Pharmacodynamic and Pharmacokinetic Interaction Studies of Loreclezole with Felbamate, Lamotrigine, Topiramate, and Oxcarbazepine in the Mouse Maximal Electroshock Seizure ModelEPILEPSIA, Issue 3 2005Jarogniew J. Luszczki Summary:,Purpose: The study investigated the types of interactions between loreclezole (LCZ) and a variety of newly licensed antiepileptic drugs (AEDs) with different mechanisms of actions [felbamate (FBM), lamotrigine (LTG), topiramate (TPM), and oxcarbazepine (OXC)] by isobolographic analysis. Methods: Anticonvulsant and adverse-effect profiles of combinations of LCZ with other AEDs at fixed ratios of 1:3, 1:1, and 3:1 were investigated in the maximal electroshock (MES)-induced seizures and the chimney test (as a measure of motor impairment) in mice so as to identify optimal combinations. Protective indices (PIs) and benefit indices (BIs) were calculated so that a ranking in relation to advantageous combinations could be established. Results: With isobolography, it was observed that the combination of LCZ and TPM, at the fixed ratios of 1:1 and 3:1, was supraadditive (synergistic; p < 0.05), whereas LCZ with TPM at the fixed ratio of 1:3 and LCZ combined with LTG, FBM, or OXC at the fixed ratios of 1:3, 1:1, and 3:1 were associated with additive interactions. Moreover, the isobolographic analysis in the chimney test revealed that only one combination tested (LCZ and TPM at the fixed ratio of 1:1) was subadditive (antagonistic; p < 0.05), whereas the remaining combinations of LCZ with LTG, FBM, or OXC (at the fixed ratios of 1:3, 1:1, and 3:1) barely displayed additivity. However, these combinations were associated with significant pharmacokinetic interactions, in that LCZ increased brain TPM (94%), OXC (21%), FBM (46%), and LTG (8%) concentrations. In addition, brain LCZ concentrations were decreased by TPM (26%), OXC (37%), LTG (42%), and FBM (19%). None of the examined combinations between LCZ and TPM, OXC, LTG, and FBM altered long-term memory in the step-through passive-avoidance task. Conclusions: LCZ plus TPM appears to be a particularly favorable combination, based on the MES test and the chimney test. LCZ and OXC also is a favorable combination. However, these conclusions are confounded by the fact that LCZ is associated with significant pharmacokinetic interactions. [source] Soot,additive interactions in engine oilsLUBRICATION SCIENCE, Issue 1 2010Dairene Uy Abstract Soot is known to cause engine wear. In this work, we focus on how engine oil formulation affects soot-related wear, and how the lubricant-derived anti-wear film changes when soot is present. Friction and wear experiments of fully and partially formulated diesel engine oils (containing basestock, dispersants and viscosity modifiers) are conducted with a ball-on-disk rig in the presence of carbon black (CB) as a soot surrogate. The friction coefficient was largely unaffected by CB dispersed in the oils, but electrically insulating film formation, an indication of the formation of anti-wear films, was decreased. Wear on the disk was found to either remain the same or decrease when CB was present, depending on the oil formulation. An examination of the lubricant-derived films using Raman and Auger electron spectroscopies found that the presence of more abundant amorphous carbon and lesser amounts of anti-wear film components on the surface was associated with higher wear. Copyright © 2009 John Wiley & Sons, Ltd. [source] Analgesic, antipyretic and Ulcerogenic properties of an indigenous formulation , KalpaamruthaaPHYTOTHERAPY RESEARCH, Issue 6 2007Rajendran Mythilypriya Abstract A modified indigenous Siddha formulation Kalpaamruthaa (KA), containing Semecarpus anacardium nut milk extract (SA), dried powder of Emblica officinalis (EO) fruit and honey was evaluated for its analgesic, antipyretic and Ulcerogenic properties. Both SA and KA, at a dose of 150 mg/kg b. wt were compared with the standard drug diclofenac sodium. KA exhibited an enhanced effect on all properties compared with that found with sole SA treatment, and is likely to be due to synergistic and additive interactions within the complex mixture of phytochemicals present in KA. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||