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Complete Degradation (complete + degradation)
Selected AbstractsTissue response to polyglycolide, polydioxanone, polylevolactide, and metallic pins in cancellous bone: An experimental study on rabbitsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 8 2006Harri Pihlajamäki Abstract The purpose of this study was to investigate, qualitatively and histoquantitatively, the tissue response of rabbit femur cancellous bone to polyglycolide (PGA), polydioxanone (PDS), polylevolactide (PLLA), and stainless steel pins under identical conditions. Eighty knees in 50 rabbits were operated on by inserting bioabsorbable pins (PGA, PDS, or PLLA) together with metallic Kirschner wire in 60, and two metallic Kirschner wires alone in 20 knees, while 20 knees served as intact controls. Follow-up times were 3, 6, 12, 24, and 52 weeks. Cancellous bone tissue response to implants was studied using histological, histomorphometrical, microradiographical, and oxytetracycline fluorescence methods. Residual fragments of PGA and PDS were seen at 24 weeks. Complete degradation of these polymers had taken place before 52 weeks. No signs of degradation of the PLLA pins were observed within the entire follow-up period. The osteoid formation surfaces at tissue implant-interface were statistically larger in all test groups as compared to intact controls. The number of macrophages at tissue implant-interfaces increased in all bioabsorbable implant specimens until 6 weeks, and with PGA until 12 weeks. No differences in the osseous response emerged when comparing groups of bioabsorbable implants with each other or with stainless steel group. Bioabsorbable pins and metallic Kirschner wires evoked an osteoconductive response in the cancellous bone surrounding implant, but the response intensity between implants displayed no differences. This suggests a simple, nonspecific walling-off new-bone front type of response. Consequently, the polymers possessed no specific osteostimulatory or osteoinhibitory properties. Within the follow-up, no significant differences in biocompatibility between the implants appeared, and no frank inflammatory foreign-body reactions occurred. The small-volume pins obviously did not exceed the local tissue tolerance and clearing capacity of the bone. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1597,1606, 2006 [source] Search of Microorganisms that Degrade PAHs under Alkaline ConditionsENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2004A. Gerbeth Abstract Bacterial strains were enriched from building rubble contaminated with polycyclic aromatic hydrocarbons (PAHs). These strains were studied as an inoculum in bioremediation processes with contaminated building rubble. The selection criteria for the bacteria were broad profiles in PAH degradation, stable expression of the traits and tolerance to alkaline conditions. Various strains of Micrococcus sp., Dietzia sp., Rhodococcus sp. and Pseudomonas sp. met the selection criteria. In general, degradative activity was limited at higher pH values. Strains of Micrococcus were suitable for practical use as complete degradation of various PAHs was observed at pH values exceeding 10. Strains of Dietzia sp. showed broad PAH degradation profile, but in some cases degradation came to a halt leaving some of the PAHs unutilized. With Dietzia sp. this could be due to inhibitory effects from the accumulation of toxic PAH metabolic products and/or growth-limiting media conditions. [source] The Implications of Polymer Selection in Regenerative Medicine: A Comparison of Amorphous and Semi-Crystalline Polymer for Tissue RegenerationADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Michelle D. Kofron Abstract Biodegradable polymeric scaffolds are being investigated as scaffolding materials for use in regenerative medicine. While the in vivo evaluation of various three-dimensional (3D), porous, biodegradable polymeric scaffolds has been reported, most studies are ,3 months in duration, which is typically prior to bulk polymer degradation, a critical event that may initiate an inflammatory response and inhibit tissue formation. Here, a 6,month in vitro degradation and corresponding in vivo studies that characterized scaffold changes during complete degradation of an amorphous, 3D poly(lactide- co -glycolide)(3D-PLAGA) scaffold and near-complete degradation of a semi-crystalline3D-PLAGA scaffold are reported. Using sintered microsphere matrix technology, constructs were fabricated in a tubular shape, with the longitudinal axis void and a median pore size that mimicked the architecture of native bone. Long-term quantitative measurements of molecular weight, mechanical properties, and porosity provided a basis for theorization of the scaffold degradation process. Following implantation in a critical size ulnar defect model, histological analysis and quantitative microCT indicated early solubilization of the semi-crystalline polymer created an acidic microenvironment that inhibited mineralized tissue formation. Thus, the use of amorphous over semi-crystalline PLAGA materials is advocated for applications in regenerative medicine. [source] A New Generation of Catalytic Poly(vinylidene fluoride) Membranes: Coupling Plasma Treatment with Chemical Immobilization of Tungsten-Based Catalysts ,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2006C. Lopez Abstract A new generation of catalytically active membranes for secondary amine oxidation and phenol degradation has been developed by coupling the advantages of low-temperature plasma-modification processes with surface chemical immobilization reactions of catalysts. Poly(vinylidene fluoride) membranes have been modified with NH3 radiofrequency glow discharges in order to graft amino groups at their surface, providing active sites for stable immobilization of tungsten-based heterogeneous catalysts. Particular attention has been focused on tungstate, WO42,, and decatungstate, W10O324,, which act efficiently as catalysts for the oxidation of secondary amines and as photocatalysts for the degradation of organic pollutants, respectively. Plasma-modified membranes surface-tailored with WO42, have been used in catalytic membrane reactors to activate hydrogen peroxide for oxidizing secondary amines to nitrones; membranes modified with W10O324, have been used for the complete degradation of phenol. The obtained results, in terms of amine,nitrone conversion and phenol degradation, respectively, appear extremely promising; these modified membranes can be considered as a pioneering, successful example of heterogenization of W-based catalysts on plasma-treated membranes. [source] Controlled Degradability of Polysaccharide Multilayer Films In Vitro and In Vivo,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2005C. Picart Abstract This article demonstrates the possibility of tuning the degradability of polysaccharide multilayer films in vitro and in vivo. Chitosan and hyaluronan multilayer films (CHI/HA) were either native or crosslinked using a water soluble carbodiimide, 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide (EDC) at various concentrations in combination with N-hydroxysulfosuccinimide. The in-vitro degradation of the films in contact with lysozyme and hyaluronidase was followed by quartz crystal microbalance measurements, fluorimetry, and confocal laser scanning microscopy after labeling of the chitosan with fluorescein isothiocyanate (CHIFITC). The native films were subjected to degradation by these enzymes, and the crosslinked films were more resistant to enzymatic degradation. Films made of chitosan of medium molecular weight were more resistant than films made of chitosan-oligosaccharides. The films were also brought in contact with plasma, which induced a change in film structure for the native film but did not have any effect on the crosslinked film. The in-vitro study shows that macrophages can degrade all types of films and internalize the chitosan. The in-vivo degradation of the films implanted in mouse peritoneal cavity for a week again showed an almost complete degradation of the native films, whereas the crosslinked films were only partially degraded. Taken together, these results suggest that polysaccharide multilayer films are of potential interest for in-vivo applications as biodegradable coatings, and that degradation can be tuned by using chitosan of different molecular weights and by controlling film crosslinking. [source] Simple radioactive assay for the estimation of DNA breaksJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2002R. Sreekumaran Nair Abstract The intactness of DNA is an important part of the normal cellular structure. Any change to the DNA in the form of breaks leads to a change in the integrity, which in turn leads to abnormality in the cellular activity. Many discrepancies have been reported among the various methods of detecting DNA damage. Here, a simple, sensitive and reproducible method has been developed for the detection of DNA breaks by radioactive labelling of 5, broken ends. The method was evaluated by studying chemically induced DNA damage by using both organochloride (2,4-dichlorophenoxyacetic acid and lindane) and organophosphorus (sevin and phosphamidon) compounds at different concentrations. Phosphamidon, one of the organophosphorus compounds studied, showed complete degradation of the DNA after treatment. Radioactive analysis of phosphamidon showed higher counts at the lowest concentration (20 µg) of the chemical when compared with the control (2752 scintillation counts per minute, scm). Studies on the chemically induced DNA breaks by radiolabelling revealed that the cumulative effect of the organophosphorus and organochloride compounds showed maximum counts in all the samples (the highest being 2904 scm) when compared with the organophosphorus and organochloride compounds studied separately (the highest being 1881 and 2260 scm, respectively). Radiolabelling studies on the blood samples of 23 pesticide workers by the newly developed assay showed a significant positive correlation (0.893) between the number of years of exposure and the scintillation counts. A maximum of 11 702 scm (for 18 years of exposure) and a minimum of 1682 scm (for 4 years of exposure) were recorded compared with 1253 scm for the negative control. This method can be used effectively for estimation of the DNA breaks, irrespective of its nature. Copyright © 2002 John Wiley & Sons, Ltd. [source] Mouse spermatozoa contain a nuclease that is activated by pretreatment with EGTA and subsequent calcium incubationJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2008Segal M. Boaz Abstract We demonstrated that mouse spermatozoa cleave their DNA into ,50 kb loop-sized fragments with topoisomerase IIB when treated with MnCl2 and CaCl2 in a process we term sperm chromatin fragmentation (SCF). SCF can be reversed by EDTA. A nuclease then further degrades the DNA in a process we term sperm DNA degradation (SDD). MnCl2 alone could elicit this activity, but CaCl2 had no effect. Here, we demonstrate the existence of a nuclease in the vas deferens that can be activated by ethylene glycol tetraacetic acid (EGTA) to digest the sperm DNA by SDD. Spermatozoa were extracted with salt and dithiothreitol to remove protamines and then incubated with EGTA. Next, the EGTA was removed and divalent cations were added. We found that Mn2+, Ca2+, or Zn2+ could each activate SDD in spermatozoa but Mg2+ could not. When the reaction was slowed by incubation on ice, EGTA pretreatment followed by incubation in Ca2+ elicited the reversible fragmentation of sperm DNA evident in SCF. When the reactions were then incubated at 37°C they progressed to the more complete degradation of DNA by SDD. EDTA could also be used to activate the nuclease, but required a higher concentration than EGTA. This EGTA-activatable nuclease activity was found in each fraction of the vas deferens plasma: in the spermatozoa, in the surrounding fluid, and in the insoluble components in the fluid. These results suggest that this sperm nuclease is regulated by a mechanism that is sensitive to EGTA, possibly by removing inhibition of a calcium binding protein. J. Cell. Biochem. 103: 1636,1645, 2008. © 2007 Wiley-Liss, Inc. [source] Photocatalytic degradation of methyl tert -butyl ether (MTBE) in contaminated water by ZnO nanoparticlesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2008Akbar Eslami Abstract BACKGROUND: Over the past several decades methyl tert -butyl ether (MTBE) as additive to gasoline, intended to either boost ratings of fuel or to reduce air pollution, has been accepted worldwide. Since MTBE has high water solubility, the occurrence of fuel spills or leaks from underground storage tanks or transferring pipeline has led to the contamination of natural waters. In this study the degradation of aqueous MTBE at relatively high concentrations was investigated by a UV-visible/ZnO/H2O2 photocatalytic process. The effects of important operational parameters such as pH, amount of H2O2, catalyst loading and irradiation time were also investigated. Concentration of MTBE and intermediates such as tert -butyl formate and tert -butyl alcohol were measured. RESULTS: Time required for complete degradation increased from 20 to 150 min when the initial concentration was increased from 10 to 500 mg L,1. The first-order rate constants for degradation of MTBE were estimated to be 0.183,0.022 min,1 as the concentration increased from 10 to 500 mg L,1. Study of the overall mineralization monitored by total organic carbon analysis showed that at an initial concentration of 100 mg L,1 MTBE complete mineralization was obtained after 100 min under UV-visible/ZnO/H2O2 photocatalysis. CONCLUSION: The data presented in this paper clearly indicated that UV-visible/ZnO/O2 as an advanced oxidation process provides an efficient treatment alternative for the remediation of MTBE-contaminated waters. Copyright © 2008 Society of Chemical Industry [source] Oxidative degradation of 4-nitrophenol in UV-illuminated titania suspensionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2001Jimmy Lea Abstract An internally-irradiated annular photoreactor has been used to investigate the oxidative degradation of aqueous 4-nitrophenol with titania as the photocatalyst. Reaction runs were performed over a 3-h period and in practically all cases, complete degradation was possible within about 2,h. The kinetics was determined as a function of nitrophenol concentration, oxygen partial pressure, catalyst loading, pH, temperature and light intensity. The reaction was characterised by a relatively low activation energy of 7.83,kJ,mol,1 although transport intrusions were negligible. Rate decreased almost exponentially with pH while a quadratic (maximum) behaviour with respect to both oxygen pressure and nitrophenol concentration is symptomatic of self-inhibition possibly due to the formation of intermediates which competitively adsorb on similar sites to the reactants. Increased catalyst dosage also improved the reaction rate although the possible effects of light scattering and solution opacity caused a drop at loadings higher than about 1.20,g,dm,3. Rate, however, has a linear dependency on light intensity, suggesting that hole,electron recombination processes were negligible at the conditions investigated. © 2001 Society of Chemical Industry [source] Remodelling of the vertebral axis during metamorphic shrinkage in the pearlfishJOURNAL OF FISH BIOLOGY, Issue 1 2004E. Parmentier Body shortening was observed in the pearlfish Carapus homei during metamorphosis. The tenuis larva at first possessed a suite of osseous vertebral bodies of similar length. The reduction in both the number and size of vertebrae followed increasing decalcification, degeneration of organic tissue and shortening. This involved a complete degradation and disappearance of the caudal tip vertebrae, and there was a reduction in the size of most of the remaining vertebrae. The further development of the vertebrae began with ossification of the neural and haemal arches before that of the vertebral body. This second part of the development followed a gradient: a gradual decreases towards the caudal tip in the size of the vertebrae and their completeness. [source] Phytate content and phytate degradation by endogenous phytase in pea (Pisum sativum)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2001Mattias Fredrikson Abstract In order to rapidly reduce the content of inositol tri,hexaphosphates in pea flour by action of the endogenous phytase, raw materials as well as incubation conditions have been evaluated. The phytate (inositol hexaphosphate) content was analysed in 27 pea varieties; the influence of storage time and the difference in phytate content between the germ and the cotyledon were determined. Furthermore, degradation of inositol phosphates by the endogenous phytase enzyme was studied in pea flour, germ and cotyledon. To find the maximum phytate degradation, the effects of temperature and pH during pea flour incubation were investigated. The most efficient phytate degradation in pea flour incubation was achieved at pH 7.5 and 45,°C. At this condition an almost complete degradation of phytate and a 66% reduction in the sum of inositol hexa-, penta-, tetra- and triphosphates were reached in 10,h. The storage time of pea seeds or removal of the germ did not have a major effect on the phytate content. Since several inositol pentaphosphate isomers were produced during phytate degradation, it can be concluded that peas contain several phytate-degrading enzymes, or one phytate-degrading enzyme with unspecific initial hydrolysation pattern. © 2001 Society of Chemical Industry. [source] Involvement of Clp protease activity in modulating the Bacillus subtilis,W stress responseMOLECULAR MICROBIOLOGY, Issue 6 2006Stephan Zellmeier Summary The induction of Bacillus subtilis genes controlled by the extracytoplasmic function alternative sigma factor ,W is strongly impaired in a strain deleted for the ClpP peptidase gene and in a double knockout of the ClpX and ClpE ATPase genes. Truncated soluble forms of the ,W anti-sigma factor RsiW are stabilized in a clpP minus strain as revealed by the green fluorescent reporter protein fused to the N-terminus of RsiW and by pulse-chase experiments. Conserved alanine residues are present in the transmembrane region of RsiW, and mutations in these positions abolish induction of ,W -controlled genes. Following alkaline shock, a truncated cytoplasmic form of RsiW is detectable in a strain expressing a triple alanine mutant allele of rsiW. These data point to a mechanism where the trans -membrane segment of RsiW contains a cryptic proteolytic tag that is uncovered as a result of intramembrane proteolysis of RsiW by RasP (YluC). After RasP-clipped RsiW is detached from the membrane, this proteolytic tag becomes crucial for the complete degradation of RsiW by cytoplasmic proteases and the release of ,W. ClpXP plays a major role in this third proteolytic step of stress-induced degradation of RsiW. Overexpression of SsrA-tagged green fluorescent protein as a ClpXP substrate protein reduces alkali induction of a ,W -controlled gene by a factor of about three, indicating that a titration mechanism is able to tune the ,W -mediated stress response to the cellular state. [source] Photodynamic Treatment of the Dermatophyte Trichophyton rubrum and its Microconidia with Porphyrin Photosensitizers,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2004Threes G. M. Smijs ABSTRACT The application of photosensitizers for the treatment of fungal infections is a new and promising development within the field of photodynamic treatment (PDT). Dermatophytes, fungi that can cause infections of the skin, hair and nails, are able to feed on keratin. Superficial mycoses are probably the most prevalent of infectious diseases in all parts of the world. One of the most important restrictions of the current therapeutic options is the return of the infection and the duration of the treatment. This is especially true in the case of infections of the nail (tinea unguium) caused by Trichophyton rubrum, an anthropophilic dermatophyte with a worldwide distribution. Recently, we demonstrated that 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) and deuteroporphyrin monomethylester were excellent photosensitizers toward T. rubrum when using broadband white light. This study demonstrates the photodynamic activity of these photosensitizers with red light toward both a suspension culture of T. rubrum and its isolated microconidia. The higher penetration depth of red light is important for the PDT of nail infections. In addition, we tested the photodynamic activity of a newly synthesized porphyrin, quinolino-[4,5,6,7-efg]-7-demethyl-8-deethylmesoporphyrin dimethylester, displaying a distinct peak in the red part of the spectrum. However, its photodynamic activity with red light toward a suspension culture of T. rubrum appeared to be only fungistatic. Sylsens B was the best photosensitizer toward both T. rubrum and its microconidia. A complete inactivation of the fungal spores and destruction of the fungal hyphae was found. In studies into the photostability, Sylsens B appeared to be photostable under the conditions used for fungal PDT. A promising result of this study is the demonstration of the complete degradation of the fungal hyphae in the time after the PDT and the inactivation of fungal spores, both with red light. These results offer the ingredients for a future treatment of fungal infections, including those of the nail. [source] Growth and phenotype of potato plants expressing an antisense gene of P-protein of glycine decarboxylase under control of a promoter with preference for the mesophyllANNALS OF APPLIED BIOLOGY, Issue 1 2001T WINZER Summary A cDNA encoding P-protein of glycine decarboxylase was expressed in antisense orientation in leaves of potato (Solanum tuberosum cv. Solara) under control of the promoter of a P-protein gene of glycine decarboxylase from Flaveria pringlei. This promoter targets gene expression preferentially to the leaf mesophyll cells. In two of the transgenic lines, mitochondria oxidise glycine only with extremely low rates. Phenotypically, these transgenic lines were only marginally different from wild type plants under ambient carbon dioxide concentrations and indistinguishable from wild type plants when grown under 800 ppm carbon dioxide. When grown in ambient carbon dioxide, transgenic plants accumulated high amounts of glycine during the light period followed by nearly complete degradation in the following night. [source] Structure,specificity relationships of an intracellular xylanase from Geobacillus stearothermophilusACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2007V. Solomon Geobacillus stearothermophilus T-6 is a thermophilic Gram-positive bacterium that produces two selective family 10 xylanases which both take part in the complete degradation and utilization of the xylan polymer. The two xylanases exhibit significantly different substrate specificities. While the extracellular xylanase (XT6; MW 43.8,kDa) hydrolyzes the long and branched native xylan polymer, the intracellular xylanase (IXT6; MW 38.6,kDa) preferentially hydrolyzes only short xylo-oligosaccharides. In this study, the detailed three-dimensional structure of IXT6 is reported, as determined by X-ray crystallography. It was initially solved by molecular replacement and then refined at 1.45,Å resolution to a final R factor of 15.0% and an Rfree of 19.0%. As expected, the structure forms the classical (,/,)8 fold, in which the two catalytic residues (Glu134 and Glu241) are located on the inner surface of the central cavity. The structure of IXT6 was compared with the highly homologous extracellular xylanase XT6, revealing a number of structural differences between the active sites of the two enzymes. In particular, structural differences derived from the unique subdomain in the carboxy-terminal region of XT6, which is completely absent in IXT6. These structural modifications may account for the significant differences in the substrate specificities of these otherwise very similar enzymes. [source] Indirect Electrochemical Oxidation of Phenol in the Presence of Chloride for Wastewater TreatmentCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2005D. Rajkumar Abstract Electrochemical oxidation of phenol using a Ti/TiO2 -RuO2 -IrO2 anode in the presence of chloride as the supporting electrolyte was investigated. The experiments were performed in an undivided batch reactor. Preliminary investigations showed that only a small fraction of phenol was oxidized by direct electrolysis, while complete degradation of phenol was achieved by indirect electrochemical oxidation using chloride as a supporting electrolyte. The effect of operating parameters such as initial pH, supporting electrolyte concentration, phenol concentration, and charge input was studied using Box-Behnken second order composite experimental design. The effect of current density on COD removal was studied separately. TOC removal and AOX formation were studied for selected conditions. It was found that the formation of chlorinated organic compounds was pronounced at the beginning of electrolysis, but it was reduced to lower levels by extended electrolysis. [source] 4156: Inflammatory mediators in the aqueous humor from patients with uveitis associated with Behēet's disease and Vogt-Koyanagi-Harada diseaseACTA OPHTHALMOLOGICA, Issue 2010A ABU EL ASRAR Purpose We studied interphotoreceptor retinoid-binding protein (IRBP), a dominant autoimmune antigen in the eye. Methods Aqueous humour samples from 28 patients with active uveitis were analysed for immunoglobulin G (IgG) content as a marker for blood-ocular barrier breakdown and by gelatinase B zymography for the detection of inflammation. The data were correlated with the presence of intact IRBP (approximately 140 kD) as determined by Western blot analysis and with the clinical disease activity. Results Aqueous humour samples from control eyes and eyes with low disease activity showed positive immunoreactivity for intact IRBP. The IRBP signal weakened or disappeared with higher disease activity. Significant positive correlations were observed between disease activity and levels of gelatinase B/matrix metalloproteinase-9 (MMP-9) (rs=0.713; P<0.001) and IgG (rs=0.580; P=0.001). Significant negative correlations were found between levels of IRBP and disease activity (rs=-0.520; P=0.005) and levels of MMP-9 (rs=-0.727; P<0.001) and of IgG (rs=-0.834; P<0.001). Whereas neutrophil elastase converted intact IRBP into an immunoreactive 55 kD peptide in vitro, the conversion by neutrophil degranulates resembled more the in vivo context with a complete degradation of IRBP. Reversal of inflammation with immunosuppressive therapy was accompanied with reappearance of intact IRBP and disappearance of IgG and MMP-9. Conclusion The analysis of IRBP proteolysis is useful as a biomarker for uveitis and suggests that inhibition of proteinases might become a therapeutic strategy in an inflammatory context of a damaged blood-ocular barrier. [source] | |||||||||||||