Cardiac Oxidative Signaling and Physiological Hypertrophy in the Na/K-ATPase α1s/sα2s/s Mouse Model of High Affinity for Cardiotonic Steroids

The Na/K-ATPase is the specific receptor for cardiotonic steroids (CTS) such as ouabain and digoxin. At pharmacological concentrations used in the treatment of cardiac conditions, CTS inhibit the ion-pumping function of Na/K-ATPase. At much lower concentrations, in the range of those reported for endogenous CTS in the blood, they stimulate hypertrophic growth of cultured cardiac myocytes through initiation of a Na/K-ATPase-mediated and reactive oxygen species (ROS)-dependent signaling. To examine a possible effect of endogenous concentrations of CTS on cardiac structure and function in vivo, we compared mice expressing the naturally resistant Na/K-ATPase α1 and age-matched mice genetically engineered to express a mutated Na/K-ATPase α1 with high affinity for CTS. In this model, total cardiac Na/K-ATPase activity, α1, α2, and β1 protein content remained unchanged, and the cardiac Na/K-ATPase dose–response curve to ouabain shifted to the left as expected. In males aged 3–6 months, increased α1 sensitivity to CTS resulted in a significant increase in cardiac carbonylated protein content, suggesting that ROS production was elevated. A moderate but significant increase of about 15% of the heart-weight-to-tibia-length ratio accompanied by an increase in the myocyte cross-sectional area was detected. Echocardiographic analyses did not reveal any change in cardiac function, and there was no fibrosis or re-expression of the fetal gene program. RNA sequencing analysis indicated that pathways related to energy metabolism were upregulated, while those related to extracellular matrix organization were downregulated. Consistent with a functional role of the latter, an angiotensin-II challenge that triggered fibrosis in the α1^r/rα2^s/s mouse failed to do so in the α1^s/sα2^s/s. Taken together, these results are indicative of a link between circulating CTS, Na/K-ATPase α1, ROS, and physiological cardiac hypertrophy in mice under baseline laboratory conditions.     

Structure–property relationships for sulfonated poly(butylene terephthalate)

Structure–property relationships have been developed for sulfonated poly(butylene terephthalate) copolymers. The compositional variables investigated were sulfonate content, molecular weight, and polymer endgroup composition, and the fundamental polymer properties evaluated were melt viscosity, crystallization kinetics, and impact strength. It was found that all compositional variables significantly affect all of the polymer properties of interest. The most interesting effect is the influence of polymer endgroup composition on polymer properties. The trends indicate that the carboxylic acid endgroups form intermolecular interactions with sodium sulfonate groups, resulting in a decrease in the strength of intermolecular ionic interactions between sodium sulfonate groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4662–4771, 2006     

Tailoring HASE rheology through polymer design: Effects of hydrophobe size, acid content, and molecular weight

Hydrophobically modified alkali-soluble emulsion (HASE) polymers are an important class of rheology modifiers for waterborne coatings applications. They are typically prepared as terpolymers by emulsion polymerization of ethyl acrylate (EA), methacrylic acid (MAA), and an associative macromonomer. The viscosity development and shear responses of HASE solutions depend on a number of factors. This article presents rheological data reflecting the impacts of three key variables: hydrophobe size, acid content, and molecular weight, on model HASE thickening and rheological performance. The relative contributions of hydrophobic association, chain expansion, and polymer chain length are discussed. In steady shear flow, all thickener solutions approached some constant low-shear viscosity at small deformation rates. At the same molar composition, larger hydrophobe size resulted in higher viscosity development and greater shear thinning behavior. The amount of acid monomer in HASE polymers can influence the balance between hydrophobic attraction and electrostatic repulsion forces. It was found that a minimum of 15 wt% MAA was required to effect dissolution and thickening of the model HASE polymers. Increasing the MAA level yielded higher zero-shear viscosity and storage modulus G’ with maximal values being obtained at 40% MAA. The molecular weight of the model thickeners was controlled by the amount of chain transfer agent (CTA) added during polymerization. When the CTA level was below 0.1 wt% based on total monomers, the polymer solutions displayed shear-thinning behavior. A small increase in CTA concentration beyond 0.1% resulted in a dramatic change to Newtonian flow, and the solution viscosity was nearly two orders of magnitude lower. The model thickeners were also tested in a vinyl acrylic architectural paint formulation. The effects of each individual factor on paint thickener efficiency, high-shear, and low-shear properties are discussed and compared with solution rheology for predictive relationships. Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 11–12, 2003, in Philadelphia, PA.     

The molecular weight distribution and oligomers of sodium hydroxide hydrolyzed poly(ethylene terephthalate)

Methanolic sodium hydroxide reacted more quickly than aqueous sodium hydroxide with poly(ethylene terephthalate) (PET). Larger amounts of low molecular weight deposits were formed at the product surface after the former treatment, also indicating the severity of this attack. The molecular weight distribution, obtained by gel permeation chromatography for the product of methanolic NaOH hydrolysis, had a population with 2400 peak molecular weight, which was not present on the chromatograph of the aqueous sodium hydroxide hydrolyzed product. This population is hypothesized to have been crystalline material. Extraction and analysis by high performance liquid chromatography of the low molecular weight products on the surface and in the bulk of the hydrolyzed PET samples, in comparison to controls, revealed the presence of more oligomeric species after hydrolysis. Also, more oligomeric species were present in the bulk extract of the methanolic sodium hydroxide hydrolyzed sample than in the aqueous NaOH hydrolyzed product.     

Performance of Methanol Oxidation Catalysts with Varying Pt:Ru Ratio as a Function of Temperature

This paper describes the effects of varying the Pt to Ru ratio in carbon-supported catalysts for methanol oxidation as a function of temperature. Previously these effects were studied in isolation, but now it is shown that the composition of a given catalyst as a function of temperature is extremely important for its activity towards methanol oxidation. Platinum rich 3:2 atomic ratio catalysts perform better than a 1:1 catalyst at 25 °C, where only Pt is believed to be active towards methanol dehydrogenation, since this process is a highly thermally activated process on Ru sites. This result is reversed at 65 °C, where the 1:1 catalyst displays much higher currents across the entire range of polarization. This may result from methanol dehydrogenation occurring on both Ru and Pt sites at higher temperatures. At an intermediate temperature, 45 °C, the 3:2 catalyst is seen to perform better at lower current values, while the 1:1 catalyst is superior at higher current densities, with the crossover occurring at 62 A g^–1. As a consequence, when designing fuel cell catalysts, the composition of the catalyst employed should be tailored with respect to the exact operating conditions, in order to promote optimum fuel cell performance.     

Carbon molecular sieve films produced by dc sputtering

This paper reports adsorption measurements that show molecular sieve effects in amorphous hydrogenated carbon (a-C : H) films deposited by d.c. magnetron discharge decomposition of acetylene. Adsorption of organic gases on the films is studied by using a quartz crystal microbalance technique. The sieve effect in this material depends on both deposition and annealing conditions. Films having significant molecular sieve effects are found to be typically microporous and to have a very small characteristic micropore dimension. It is suggested that the d.c. sputtered a-C : H film may be useful as a molecular sieve material in selective adsorption and gas permeation studies.     

Review of Operating Experience Of Ozone Systems In Municipal Plants In The United States

The treatment chemical ozone has now been successfully used in the United States in municipal water and wastewater plants for many years. To insure continuous, successful operations of these applications, operating obstacles had to be dealt with and overcome.

In this paper, examples of field operating problems and their solutions are described. The experiences at specific municipal water and wastewater installations are reviewed in detail. Discussed for each example are : the background and effects of the problem, the problem-solving process, and the eventual resolution of the problem. The examples include simple unit operations to entire processes.

By observing the ozone installation's operation several years after start-up, the design of future ozone systems can be improved and operating problems minimized.