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Increased Degradation (increased + degradation)
Selected AbstractsMechanisms of renal hyporesponsiveness to ANP in heart failureEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 9 2003A. Charloux Abstract The atrial natriuretic peptide (ANP) plays an important role in chronic heart failure (CHF), delaying the progression of the disease. However, despite high ANP levels, natriuresis falls when CHF progresses from a compensated to a decompensated state, suggesting emergence of renal resistance to ANP. Several mechanisms have been proposed to explain renal hyporesponsiveness, including decreased renal ANP availability, down-regulation of natriuretic peptide receptors and altered ANP intracellular transduction signal. It has been demonstrated that the activity of neutral endopeptidase (NEP) is increased in CHF, and that its inhibition enhances renal cGMP production and renal sodium excretion. In vitro as well as in vivo studies have provided strong evidence of an increased degradation of intracellular cGMP by phosphodiesterase in CHF. In experimental models, ANP-dependent natriuresis is improved by phosphodiesterase inhibitors, which may arise as new therapeutic agents in CHF. Sodium-retaining systems likely contribute to renal hyporesponsiveness to ANP through different mechanisms. Among these systems, the renin-angiotensin-aldosterone system has received particular attention, as angiotensin II and ANP have renal actions at the same sites and inhibition of angiotensin-converting enzyme and angiotensin-receptor blockade improve ANP hyporesponsiveness. Less is known about the interactions between the sympathetic nervous system, endothelin or vasopressin and ANP, which may also blunt ANP-induced natriuresis. To summarize, renal hyporesponsiveness to ANP is probably multifactorial. New treatments designed to restore renal ANP efficiency should limit sodium retention in CHF patients and thus delay the progression to overt heart failure. [source] Interactive effects of elevated CO2, N deposition and climate change on extracellular enzyme activity and soil density fractionation in a California annual grasslandGLOBAL CHANGE BIOLOGY, Issue 10 2005Hugh A. L. Henry Abstract Elevated CO2, N deposition and climate change can alter ecosystem-level nutrient cycling both directly and indirectly. We explored the interactive effects of these environmental changes on extracellular enzyme activity and organic matter fractionation in soils of a California annual grassland. The activities of hydrolases (polysaccharide-degrading enzymes and phosphatase) increased significantly in response to nitrate addition, which coincided with an increase in soluble C concentrations under ambient CO2. Water addition and elevated CO2 had negative but nonadditive effects on the activities of these enzymes. In contrast, water addition resulted in an increase in the activities of lignin-degrading enzymes (phenol oxidase and peroxidase), and a decrease in the free light fraction (FLF) of soil organic matter. Independent of treatment effects, lignin content in the FLF was negatively correlated with the quantity of FLF across all samples. Lignin concentrations were lower in the aggregate-occluded light fraction (OLF) than the FLF, and there was no correlation between percent lignin and OLF quantity, which was consistent with the protection of soil organic matter in aggregates. Elevated CO2 decreased the quantity of OLF and increased the OLF lignin concentration, however, which is consistent with increased degradation resulting from increased turnover of soil aggregates. Overall, these results suggest that the effects of N addition on hydrolase activity are offset by the interactive effects of water addition and elevated CO2, whereas water and elevated CO2 may cause an increase in the breakdown of soil organic matter as a result of their effects on lignin-degrading enzymes and soil aggregation, respectively. [source] Inhibitory effects of N -acetylcysteine on scavenger receptor class A expression in human macrophagesJOURNAL OF INTERNAL MEDICINE, Issue 5 2002L. SVENSSON Abstract.,Svensson L, Norén K, Wiklund O, Lindmark H, Ohlsson B, Mattsson Hultén L (Wallenberg Laboratory for Cardiovascular Research, The Sahlgrenska Academy at Göteborg University, Göteborg; and AstraZeneca, Mölndal, Sweden). Inhibitory effects of N -acetylcysteine on scavenger receptor class A expression in human macrophages. J Intern Med 2002; 251:. Objective.,The formation of foam cells from monocyte-derived macrophages involves the uptake of modified lipoproteins by scavenger receptors. Antioxidants inhibit lipoprotein oxidation and may also modulate gene expression. We investigated the effect of the antioxidant N -acetylcysteine on the expression of the class A scavenger receptor (SR-A) types I and II in human macrophages. Design.,Monocytes and macrophages from healthy blood donors and plaque-derived macrophages from patients undergoing carotid endartherectomy were used for experiments. SR-A mRNA was analysed with quantitative and semiquantitative reverse transcription-polymerase chain reaction, and ligand binding and uptake were assessed with 125I-labelled acetylated low-density lipoprotein (LDL). Results.,Incubation of monocytes and monocyte-derived macrophages with N -acetylcysteine decreased both SR-A I and II mRNA expression. N -Acetylcysteine also reduced SR-A mRNA in lesion-derived cells. Binding and uptake of 125I-acetylated LDL was decreased after brief incubation with N -acetylcysteine. After longer periods of incubation with N -acetylcysteine we observed an increased degradation of lipoproteins. Conclusions.,Our results imply that N -acetylcysteine leads to a decrease in SR-A mRNA and initially also to an attenuated uptake of modified lipoproteins. This adds more to the knowledge about the cellular actions of this drug. [source] Water Absorption and Degradation Characteristics of Chitosan-Based Polyesters and Hydroxyapatite CompositesMACROMOLECULAR BIOSCIENCE, Issue 3 2007Vitor M. Correlo Abstract Blends of chitosan and biodegradable synthetic aliphatic polyesters (polycaprolactone, poly(butylene succinate), poly[(butylene succinate)- co -adipate], poly[(butylene terephthalate)- co -adipate], and poly(lactic acid)) were injection-molded. These samples were immersed in isotonic solution at 37,°C for a period of 60 d. The water uptake and the degradation properties, as measured by the loss in tensile strength, were evaluated as a function of time. In this study, the rate and the equilibrium water uptake were proportional to the amount of chitosan in the blend. The addition of HA to chitosan and polyester significantly reduced the equilibrium water uptake. The water uptake did not follow the classical Fickian phenomena and could be expressed by a two-stage sorption non-Fickian diffusion model. Contact angle measurement was used to quantify the changes in surface hydrophilicity as a function of chitosan and polyester composition. The glycerol contact angle decreased with increasing synthetic components in the blend. The blends and composites also showed increased degradation, as quantified by a loss in their mechanical properties, with increase in natural content. The degradation of properties was directly related to the water uptake of the blends; the higher the water uptake, the higher the degradation. Pure polyesters, while having low water uptake, nevertheless showed significant degradation by a precipitous drop in the strain at break. Among the polyesters, poly(lactic acid) displayed maximum degradation, while polycaprolactone displayed the least. [source] | ||||||||||