Increase In Carbonyl Content Research Articles

Functional properties of gelatin from cuttlefish ( Sepia pharaonis) skin as affected by bleaching using hydrogen peroxide

Functional properties of gelatin from dorsal and ventral skin of cuttlefish with and without bleaching by H 2O 2 at different concentrations (2% and 5% (w/v)) for 24 and 48 h were studied. Gelatin from skin bleached with 5% H 2O 2 for 48 h showed the highest yield (49.65% and 72.88% for dorsal and ventral skin, respectively). Bleaching not only improved the colour of gelatin gel by increasing the L ∗-value and decreasing a ∗-value but also enhanced the bloom strength, and the emulsifying and foaming properties of the resulting gelatin. Gelatin from bleached skin contained protein with a molecular weight of 97 kDa and had an increased carbonyl content. Fourier transform infrared spectroscopic study showed higher intermolecular interactions and denaturation of gelatin from bleached skin than that of the control. These results indicated that hydrogen peroxide most likely induced the oxidation of gelatin, resulting in the formation of gelatin cross-links, giving improved functional properties.

Carbonylated Proteins Are Detectable Only in a Degradation-Resistant Aggregate State in Escherichia coli

Carbonylation is currently used as a marker for irreversible protein oxidative damage. Several studies indicate that carbonylated proteins are more prone to degradation than their nonoxidized counterparts. In this study, we observed that in Escherichia coli, more than 95% of the total carbonyl content consisted of insoluble protein and most were cytosolic proteins. We thereby demonstrate that, in vivo, carbonylated proteins are detectable mainly in an aggregate state. Finally, we show that detectable carbonylated proteins are not degraded in vivo. Here we propose that some carbonylated proteins escape degradation in vivo by forming carbonylated protein aggregates and thus becoming nondegradable. In light of these findings, we provide evidence that the accumulation of nondegradable carbonylated protein presented in an aggregate state contributes to the increases in carbonyl content observed during senescence.

OVARIECTOMY SENSITIZES A DELETERIOUS INTERACTION BETWEEN ETHANOL WITHDRAWAL AND AGING TO A GREATER DEGREE AFTER ABRUPT TERMINATION THAN GRADUAL TERMINATION OF ETHANOL

We have demonstrated that abrupt termination of chronic ethanol diet creates lipid peroxidation in young adult rats in a manner protected by endogenous estrogen [(17(‐estradiol (E2)]. In this study, we tested whether ovariectomy exacerbates a deleterious interaction between ethanol withdrawal (EW) and age at the levels of oxidative stress using a 3 month ethanol diet paradigm. 5‐, 12‐, and 16‐month‐old ovariectomized rats with oil pellet or E2 replacement received a liquid ethanol (6.5%) or control dextrin diet for 3 months. One group was terminated from the ethanol diet by step‐down concentrations of ethanol. Another group was terminated from the ethanol diet abruptly. Cerebellum, cortex, hippocampus were collected to assess the levels of carbonyls as a marker of oxidative damage to protein. Compared to groups with control dextrin diet and gradual termination of ethanol diet, EW groups showed a greater increase in protein carbonyls. Such phenomenon was more profound in older rats vs younger rats and more profound in ovariectomized rats vs in ovary intact rats. This increase in carbonyl contents was partially prevented by E2 implantation. These findings suggest that ovariectomy sensitizes brain to a deleterious interaction of EW with age in a manner that is more prominent after abrupt termination than a gradual termination of ethanol of long term ethanol diet (supported by NIAAA AA013864 and AA015982).

Increased protein carbonylation in leaves of Arabidopsis and soybean in response to elevated [CO2

While exposure of C3 plants to elevated [CO2] would be expected to reduce production of reactive oxygen species (ROS) in leaves because of reduced photorespiratory metabolism, results obtained in the present study suggest that exposure of plants to elevated [CO2] can result in increased oxidative stress. First, in Arabidopsis and soybean, leaf protein carbonylation, a marker of oxidative stress, was often increased when plants were exposed to elevated [CO2]. In soybean, increased carbonyl content was often associated with loss of leaf chlorophyll and reduced enhancement of leaf photosynthetic rate (Pn) by elevated [CO2]. Second, two-dimensional (2-DE) difference gel electrophoresis (DIGE) analysis of proteins extracted from leaves of soybean plants grown at elevated [CO2] or [O3] revealed that both treatments altered the abundance of a similar subset of proteins, consistent with the idea that both conditions may involve an oxidative stress. The 2-DE analysis of leaf proteins was facilitated by a novel and simple procedure to remove ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from soluble soybean leaf extracts. Collectively, these findings add a new dimension to our understanding of global change biology and raise the possibility that oxidative signals can be an unexpected component of plant response to elevated [CO2].

Comparison of proteolysis in native, heat-treated and aged proteins from turkey meat

1. The present study compared the ability of native, heat-treated and aged turkey breast muscle proteins to undergo proteolysis by digestive tract proteases. 2. Domestic turkey toms were slaughtered under laboratory conditions. Breast muscles were excised immediately post mortem; one was placed under conditions to develop exudative meat by maintaining the muscle at 40°C for at least 30 min and the other was refrigerated under commercial conditions. 3. Meat was collected and stored for 7 d at 4°C. Breast samples removed at d 0 and d 7 were frozen and stored at −80°C until used for determination of solubility, protein surface hydrophobicity and protein oxidation through carbonyl content. Measurements of pepsin and trypsin/chymotrypsin activities were performed in vitro on myofibrillar proteins. 4. Storage increased carbonyl content in control samples while the oxidation increase was not significant in heat-treated myofibrillar protein. Hydrophobicity was not affected by storage time or treatment or protein solubility. 5. Storage significantly increased trypsin + chymotrypsin activity only in the control group. The activities of pepsin and trypsin + chymotrypsin were negatively correlated with protein surface hydrophobicity.

Changes in Structures of Milk Proteins upon Photo-oxidation

Changes in protein structures as a result of riboflavin-induced photo-oxidation were studied for six milk proteins: alpha-casein, beta-casein, kappa-casein, lactoferrin, alpha-lactalbumin, and beta-lactoglobulin. The milk proteins showed significant variability in sensitivity to photo-oxidation. After photo-oxidation, an increase in carbonyl content because of oxidation of tryptophan, histidine, and methionine, as well as formation of dityrosine, was observed for all proteins studied, although at very different levels. Generally, the increment was highest for alpha- and beta-casein and was lowest for lactoferrin. Loss of tryptophan because of photo-oxidation was well-correlated with the formation of the tryptophan oxidation products, N-formylkynurenine and kynurenine. Changes at the tertiary protein structure level were observed after photo-oxidation of the globular proteins, where tryptophan fluorescence emission indicated unfolding of alpha-lactalbumin and beta-lactoglobulin, whereas lactoferrin achieved a more compact tertiary structure. Changes in secondary structure were observed for alpha-lactalbumin and beta-lactoglobulin, whereas the secondary structure of lactoferrin did not change. Polymerization of alpha- and beta-casein and of lactoferrin was observed, whereas kappa-casein, alpha-lactalbumin, and beta-lactoglobulin showed little tendency to polymerize after photo-oxidation. Lability toward photo-oxidation is discussed according to the structural stabilities of the globular proteins.

Evidence that 3‐hydroxy‐3‐methylglutaric acid promotes lipid and protein oxidative damage and reduces the nonenzymatic antioxidant defenses in rat cerebral cortex

In the present work we investigated the in vitro effect of 3-hydroxy-3-methylglutarate (HMG) that accumulates in 3-hydroxy-3-methylglutaryl-CoA lyase deficiency (HMGLD) on important parameters of oxidative stress in rat cerebral cortex. It was observed that HMG induced lipid peroxidation by significantly increasing chemiluminescence and levels of thiobarbituric acid-reactive substances (TBA-RS). This effect was prevented by the antioxidants alpha-tocopherol, melatonin, N-acetylcysteine, and superoxide dismutase plus catalase, suggesting that free radicals were involved in the lipid oxidative damage. On the other hand, HMG did not change TBA-RS levels in intact or disrupted mitochondrial preparations, indicating that generation of oxidants by this organic acid was dependent on cytosolic mechanisms. HMG also induced protein oxidative damage in cortical supernatants, which was reflected by increased carbonyl content and sulfhydryl oxidation. Furthermore, HMG significantly reduced the nonenzymatic antioxidant defenses total-radical trapping antioxidant potential, total antioxidant reactivity, and reduced glutathione (GSH) levels in rat cerebral cortex. HMG-induced GSH reduction was totally blocked by melatonin pretreatment. We also verified that the decrease of GSH levels provoked by HMG in cortical supernatants was not due to a direct oxidative effect of this organic acid, because exposition of commercial GSH and purified membrane protein-bound thiol groups to HMG in the absence of cortical supernatants did not decrease the reduced sulfhydryl groups. Finally, the activities of the main antioxidant enzymes were not altered by HMG exposure. Our data indicate that oxidative stress elicited in vitro by HMG may possibly contribute at least in part to the pathophysiology of the brain injury in HMGLD.

Reactive Nitrogen Species-Dependent Effects on Soybean Chloroplasts

Nitric oxide (NO) generation by soybean (Glycine max, var ADM 4800) chloroplasts was studied by electron paramagnetic resonance (EPR) spin-trapping technique1. Both nitrite and L-arginine (arg) are the required substrates for enzymatic activities considered as possible sources of NO in plants. Soybean chloroplasts showed a NO production of 3.2 ± 0.2 nmol min-1 mg-1 protein in the presence of 1 mM NaNO2. Chloroplasts incubated with 1 mM arg showed a NO production of 0.76 ± 0.04 nmol min-1 mg-1 protein. This production was inhibited when chloroplasts were incubated in presence of NOS-inhibitors L-NAME and L-NNA. In vitro exposure of chloroplasts to a NO-donor (GSNO) decreased both ascorbyl radical content and the activity of ascorbate peroxidase, without modification of the total ascorbate content. Exposure of the isolated chloroplasts to a NO-donor decreased lipid radical content in membranes, however, incubation in the presence of 25 μM peroxynitrite (ONOO-) led to an increase in lipid-derived radicals (34%). The effect of ONOO- on protein oxidation was determined by western blotting, showing an increase in carbonyl content either in stroma or thylakoid proteins as compared to control. Taken as a whole, NO seems to be an endogenous metabolite in soybean chloroplasts and reactive nitrogen species could exert either antioxidant or prooxidant effects on chloroplasts, since both a decreased lipid radical content in membranes and a decrease in the activity of ascorbate peroxidase were observed after exposure to a NO donor.

Insinuation of exacerbated oxidative stress in sucrose-fed rats with a low dietary intake of magnesium: Evidence of oxidative damage to proteins

High sucrose diets and low magnesium intake have been independently implicated in induction of oxidative stress in animal models. The aim of this study was to investigate whether low dietary magnesium intake exacerbates the prooxidant effects of high sucrose feeding. Rats were fed control (C), high sucrose (HS); low magnesium (LM) and high sucrose low magnesium (HSLM) diets for 90 days and oxidative stress evaluated in terms of formation of TBARS, advanced oxidation protein products and protein carbonyls. HS and LM rats showed evidence of lipid peroxidation and protein oxidation in plasma and liver. Enhanced oxidative injury to lipids and proteins after HSLM feeding was indicated by increased carbonyl content (p <0.01) and significantly (p <0.005) higher levels of TBARS in plasma and hepatic tissue relative to both HS and LM groups. Altogether, these results illustrate the potential detrimental and cumulative effects of low magnesium intake combined with high sucrose consumption on oxidative stress variables.

Detection of protein carbonyls in aging liver tissue: A fluorescence-based proteomic approach

Protein carbonyls are commonly used as a marker of protein oxidation in cells and tissues. Currently, 2,4-dinitrophenyl hydrazine (DNPH) is widely used (spectrophotometrically or immunologically) to quantify the global carbonyl levels in proteins and identify the specific proteins that are carbonylated. We have adapted a fluorescence-based approach using fluorescein-5-thiosemicarbazide (FTC), to quantify the global protein carbonyls as well as the carbonyl levels on individual proteins in the proteome. Protein carbonyls generated in vitro were quantified by labeling the oxidized proteins with FTC followed by separating the FTC-labeled protein from free probe by gel electrophoresis. The reaction of FTC with protein carbonyls was found to be specific for carbonyl groups. We measured protein carbonyl levels in the livers of young and old mice, and found a significant increase (two-fold) in the global protein carbonyl levels with age. Using 2-D gel electrophoresis, we used this assay to directly measure the changes in protein carbonyl levels in specific proteins. We identified 12 proteins showing a greater than two-fold increase in carbonyl content (pmoles of carbonyls/μg of protein) with age. Most of the 12 proteins contained transition metal binding sites, with Cu/Zn superoxide dismutase containing the highest molar ratio of carbonyls in old mice. Thus, the fluorescence-based assay gives investigators the ability to identify potential target proteins that become oxidized under different pathological and physiological conditions.

Chloroplasts as a nitric oxide cellular source. Effect of reactive nitrogen species on chloroplastic lipids and proteins.

Nitric oxide (NO) generation by soybean (Glycine max var. ADM 4800) chloroplasts was studied as an endogenous product assessed by the electron paramagnetic resonance spin-trapping technique. Nitrite and l-arginine (Arg) are substrates for enzymatic activities considered to be the possible sources of NO in plants. Soybean chloroplasts showed a NO production of 3.2 +/- 0.2 nmol min(-1) mg(-1) protein in the presence of 1 mm NaNO(2). Inhibition of photosynthetic electron flow by 3-(3,4-dichlorophenyl)-1,1-dimethyl urea resulted in a lower rate (1.21 +/- 0.04 nmol min(-1) mg(-1) protein) of NO generation. Chloroplasts incubated with 1 mm Arg showed NO production of 0.76 +/- 0.04 nmol min(-1) mg(-1) protein that was not affected either by omission of Ca(2+) or by supplementation with Ca(2+) and calmodulin to the incubation medium. This production was inhibited when chloroplasts were incubated in the presence of NO synthase inhibitors N(omega)-nitro-l-Arg methyl ester hydrochloride and N(omega)-nitro-l-Arg. In vitro exposure of chloroplasts to an NO donor (250 mum S-nitrosoglutathione) decreased lipid radical content in membranes by 29%; however, incubation in the presence of 25 mum peroxynitrite (ONOO(-)) led to an increase in lipid-derived radicals (34%). The effect of ONOO(-) on protein oxidation was determined by western blotting, showing an increase in carbonyl content either in stroma or thylakoid proteins as compared to controls. Moreover, ONOO(-) treatment significantly affected both O(2) evolution and chlorophyll fluorescence in thylakoids. Data reported here suggest that NO is an endogenous metabolite in soybean chloroplasts and that reactive nitrogen species could exert either antioxidant or prooxidant effects on chloroplast macromolecules.

Comparative study of alloxan effects in copper-loaded and iron-loaded rats: lipid peroxidation, protein oxidation, proteasome and antioxidant enzyme activities

Abstract The in-vivo effects of alloxan on protein oxidation and lipid peroxidation, as well as on proteasome and antioxidant enzyme activities in liver and kidney of copper-loaded and iron-loaded rats, were studied. In control animals, a single alloxan dose (120 mg/kg, i.p.) increased blood-glucose concentration at the 24th hr and 48th hr and, especially, on the 5th day. For these periods of alloxan action, no changes in lipid peroxidation and antioxidant enzyme activities were found; only a slight increase of carbonyl content and strong increase of trypsin-like proteasome activity in rat liver on the 5th day was observed. Five days after alloxan injection, the blood-glucose concentration in iron-pretreated rats was similar to that of the controls. However, it was significantly lower in copper-pretreated animals; hence, insulin-mimetic action of copper might be suggested. The lower proteasome activity, measured in liver of copper-pretreated diabetic rats is probably due to a potential copper-chelating ability of alloxan. The present results showed that the action of alloxan was different in copper-and iron-pretreated rats. Analogous studies, using pretreatment with other metals, would contribute to a further elucidation of the role of different metals in diabetes development, especially in regions with environmental metal contamination.

Formation of phenols from the low-temperature fast pyrolysis of radiata pine ( Pinus radiata) : Part II. Interaction of molecular oxygen and substrate water

In Part I, the influence of molecular oxygen on phenolic compound formation from the low-temperature fast pyrolysis of Radiata pine ( Pinus radiata) was reported. This work is elaborated upon and includes the interaction, or dual effect, of molecular oxygen and substrate water on phenolic compound formation. Experimentation was performed on a bench scale fluidised bed system and gas chromatography/mass spectroscopy was used for product analysis. Oven-dried and ‘as received’ (9.7% moisture content) Radiata pine (150–250 μm) was processed at 290–295 °C using air, nitrogen and oxygen enriched nitrogen as the fluidising gases. The inclusion of both molecular oxygen, in the form of air, and substrate moisture in the reaction system resulted in an increase in the yield of monomeric phenols from 0.07 to 5.03% (m/m). However, the inclusion of either molecular oxygen or substrate moisture resulted in a phenolic compound yield of only 0.60 and 0.27% (m/m), respectively. It was proposed that the molecular oxygen promoted the homolytic, free radical induced, aryl ether cleavage through facilitation of free radical formation as well as through hydroperoxide formation on the aliphatic carbon associated with aryl ether linkages. This explanation was consistent with the significant increase in carbonyl content of the phenolic product when molecular oxygen was included in the reaction atmosphere. However, such carbonyl groups are quite reactive and may participate in cross-linking reactions at elevated temperatures. The positive influence of water on the yield of monomeric phenolic compounds was believed to be indirect. That is, under fast pyrolysis conditions, in which the residence time of both substrate and volatile decomposition products is short, the evaporation of water would have suppressed substrate temperature elevation, thereby suppressing the rate of cross-linking reactions, resulting in the increased preservation of carbonyl containing low molecular weight products.

Beneficial effect of vitamin E supplementation on the biochemical and kinetic properties of Tamm–Horsfall glycoprotein in hypertensive and hyperoxaluric patients

This study aimed to assess the therapeutic efficacy of oral vitamin E supplementation on the biochemical and kinetic properties of Tamm-Horsfall glycoprotein (THP) in hypertensive and hyperoxaluric patients. Newly detected hypertensives (n = 200) and stone formers (n = 200) were each subdivided into two groups. One group (n = 100) was administered the antioxidant vitamin E at 400 mg/day given as an oral supplement along with standard therapeutic drugs for hypertension and hyperoxaluria and the patients were followed for a period of 9 months. The other group (n = 100) did not receive vitamin E (placebo controls). Age and sex-matched controls (n = 100) were monitored simultaneously. THP was isolated from 24 h urine samples before and at the end of every third month during a period of 9 months from the vitamin E-treated hypertensive and hyperoxaluric groups. THP samples were also collected from control subjects, and at the end of the ninth month from placebo controls. The isolated protein was assessed for purity by SDS-PAGE. The purity-checked proteins were subjected to spectrophotometric crystallization assay, calcium oxalate (CaOx) crystal interaction studies, and biochemical analysis of sialic acid, thiol and carbonyl content. Plasma superoxide, hydroxyl radical, hydrogen peroxide and vitamin E levels as well as superoxide dismutase and catalase activities were also monitored. The THP from the hypertensive and hyperoxaluric subjects exhibited a significant promoting effect on the nucleation and aggregation phases and caused a concomitant increase in CaOx crystal interaction. The altered kinetic properties of THP in these subjects were strongly associated with increased carbonyl content and with decreased thiol and sialic acid contents. Oral administration of vitamin E to these patients caused near normalization of these biochemical alterations and satisfactorily restored the kinetic properties of THP to near normal activity. At the end of 9 months, THP isolated from placebo controls (hypertensive and hyperoxaluric) showed highly aggregated calcium oxalate monohydrate crystals as observed by light microscopy. In contrast, vitamin E-supplemented patients showed CaOx dihydrate crystals that were similar to control THP. There was an imbalance in the oxidant and antioxidant levels. For the oxidants, superoxide, hydrogen peroxide and hydroxyl radical levels were increased, and for the antioxidants, there was loss of antioxidant enzyme activities and a decline in plasma vitamin E level in both hypertensive and hyperoxaluric patients. Supplementary antioxidant (vitamin E) corrected this imbalance to near normal conditions. We hypothesize that the loss of THP inhibitory activity in the hypertensive and hyperoxaluric patients in a crystallizing medium is mediated primarily by oxidative damage to this protein. The possible occurrence of renal stones in essential hypertensive subjects, and the risk of recurrence in hyperoxaluric subjects, may be explained by oxidative damage to renal tissues that remained unchecked by standard drug therapies. The normalization of the kinetic properties of THP following vitamin E supplementation is in support of our hypothesis.

Effect of oxidative stress on the production of recombinant human interferon-gamma in Escherichia coli.

To reduce the degradation pathway of rhIFN-gamma (recombinant human interferon-gamma), the susceptibility against oxidative stress during fermentation in Escherichia coli cells and in purification process were investigated. Fermentations of recombinant E. coli were performed at 5, 30 and 60% DO (dissolved oxygen) concentrations. The expressed rhIFN-gamma is purified in three-step chromatography processes with 99.9% purity under reducing and non-reducing conditions. Recombinant IFN-gamma production, carbonyl and dimeric contents and antiviral-specific activity of purified protein were monitored. The increase in carbonyl content was taken to be an indicator of protein oxidation. DO concentration did not show any noticeable effect on rhIFN-gamma production. During fermentation, the carbonyl-group content showed no significant increase at 5 and 30% DO but a 10-fold increase at 60% DO concentration was observed. The antiviral-specific activity of purified rhIFN-gamma was decreased 35 and 69% at 30 and 60% DO concentrations respectively. After the purification process, under non-reducing conditions, the activity of purified protein decreased to 30% of its original value. The degree of dimeric forms of protein was found to depend on the O2 concentration during fermentation and purification.

Adrenocorticotropin induces heme oxygenase-1 expression in adrenal cells.

Heme oxygenase (HO) catalyzes the first and rate-controlling step of heme catabolism into biliverdin, iron and carbon monoxide. Three isoforms of HO have been identified so far: the inducible HO-1 and the constitutive HO-2 and HO-3. Both HO-1 and HO-2 were expressed in zona fasciculata (ZF) adrenal cells and in a mouse adrenocortical cell line (Y1). HO-1 but not HO-2 expression was upregulated by adrenocorticotropic hormone (ACTH) and accumulation of HO-1 protein correlated with an increase in HO activity in Y1 cells. ACTH induced HO-1 expression in a time- and dose-dependent manner with a maximum after 5 h of treatment and a threshold concentration of 0.1 mIU/ml. Actinomycin D and cycloheximide completely blocked the effect of ACTH on HO-1 mRNA expression whereas mRNA stability was not affected by ACTH. Permeable analogs of cAMP mimicked the effect of ACTH on HO-1 expression and ACTH induction was prevented by the protein kinase A (PKA) inhibitor H89. Steroid production was significantly increased when both HO-1 and HO-2 activities were inhibited by Sn-protoporphyrin IX (SnPPIX). The lipid peroxidation and increase in carbonyl content triggered by hydrogen peroxide was prevented by treatment of Y1 cells with bilirubin and ACTH.

Short-term CR decreases cardiac mitochondrial oxidant production but increases carbonyl content.

Lifelong caloric restriction (CR) reduces the rate of mitochondrial oxidant production and the accumulation of oxidized proteins and prevents some of the age-associated decline in 20S proteasome activity. However, few studies have investigated how rapidly the beneficial effects of CR take place. We investigated whether 2 mo of CR in 6-mo-old rats would be of sufficient duration to elicit these beneficial changes. Mitochondrial oxidant production was significantly diminished in the CR rats compared with the ad libitum-fed animals. Short-term CR also caused a significant decrease in mitochondrial superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities, but there were no differences in cytosolic SOD and GPX activities, whereas mitochondrial and cytosolic catalase (CAT) activity was increased with CR. However, protein carbonyl content was significantly elevated in both the mitochondrial and cytosolic fractions from CR rats. Of the three major 20S proteasome activities (chymotrypsin-like, trypsin-like, and peptidylglutamyl-peptide hydrolase), the peptidylglutamyl-peptide hydrolase activity was significantly elevated in the CR animals, possibly because of the fact that there were more oxidized proteins to be degraded. Although fewer oxidants were produced in the CR animals, it is possible that the ability to scavenge oxidants was transiently suppressed because of the reduction in mitochondrial antioxidant enzyme activities, which may explain the observed increases in carbonyl content.

ATRP grafting from cellulose fibers to create block-copolymer grafts.

Cellulose fibers, in the form of a conventional filter paper, have been modified by reacting the hydroxyl groups on the fiber surface with 2-bromoisobutyryl bromide, followed by grafting using ATRP conditions. The papers were first grafted with methyl acrylate (MA), rendering the paper very hydrophobic as reported in an earlier work. The papers were analyzed by gravimetry, FT-IR, ESCA, and AFM. To verify that the polymerization from the surface was "living", a second layer of another, hydrophilic, polymer, 2-hydroxyethyl methacrylate (HEMA), was grafted upon the PMA layer, creating a block-copolymer graft from the fibers. After the layer of PHEMA had been attached, contact angle measurements were no longer possible, because of the absorbing nature of PHEMA-grafted layer. This indicates that a copolymer had indeed been formed on the surface. FT-IR showed a large increase in carbonyl content after the PHEMA-grafting, which further proves that a layer of PHEMA was attached to the PMA layer. This goes to show that the hydrophilic/hydrophobic behavior of a cellulose surface can be tailored by the use of "living"/controlled radical polymerization methods such as ATRP.

Mitochondrial, sarcoplasmic membrane integrity and protein degradation in heart and skeletal muscle in exercised rats

Several different exercise regimens varied in the severity of tissue damage induced. Therefore, this study investigated the effects of a single bout of exercise versus endurance training in heart and skeletal muscles with different predominant fiber types on indices of mitochondrial, endoplasmic reticulum (ER) integrity and protein degradation. Male Wistar rats performed different treadmill exercise protocols: exhaustive, maximal exhaustive, eccentric, training and exhaustive exercise after training. The maximal and eccentric exercises resulted in a significant loss of integrity of the sarcoplasmic and ER muscle, while no changes were observed in cardiac muscle. Mitochondrial membrane fluidity measured by the fluorescence polarization method was significantly increased post-acute exercises in heart and oxidative muscles. Regular exercise can stabilize and preserve the viscoelastic nature of mitochondrial membranes in both tissues. The highest increase in carbonyl content was obtained in heart after exhaustive exercise protocol, from 1±0.1 to 3.6±0.14 nmol mg protein −1, such increase were not found after regular exercise with values significantly decreased. Nitrate heart levels showed attenuated generation of nitric oxide after training. Muscle protein oxidation was produced in all exhaustive exercises including eccentric exercise.

Comparison of volatile emissions and structural changes of melt reprocessed polypropylene resins

AbstractPolypropylene (PP), as a commodity recyclable thermoplastic, was studied in this research to evaluate the potential environmental impact resulting from volatile organic compounds (VOCs) emitted during multiple melt reprocessing. Unstabilized PP (U‐PP) and stabilized PP (S‐PP) resins, simulating recycled materials prone to degradation, were evaluated for total VOC emissions generated during multiple melt reprocessing by injection molding and extrusion, respectively. Results show that the maximum amount of total VOCs from each cycle (up to six cycles for extrusion and up to ten for injection molding) did not significantly change, while the cumulative VOCs increased with increasing processing cycle for both materials. A good correlation between cumulative VOC increases and melt flow index increase for the U‐PP and weight‐average molecular weight Mw decrease for the S‐PP were obtained. Reprocessing in all cases was accompanied by decreases in Mw and melt viscosity as a result of thermooxidative degradation. FTIR data considering increases in carbonyl content and degree of unsaturation suggest that at equivalent cycle numbers, degradation appears to be more severe for the extruded material in spite of the longer oxidative induction time of the “as received” pellets used in extrusion. The onset and type of structural changes are shown to depend on cycle number and reprocessing method. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 235–242, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10027