Degradative Processes (degradative + process)

Distribution by Scientific Domains


Selected Abstracts


Autophagy and amino acid homeostasis are required for chronological longevity in Saccharomyces cerevisiae

AGING CELL, Issue 4 2009
Ashley L. Alvers
Summary Following cessation of growth, yeast cells remain viable in a nondividing state for a period of time known as the chronological lifespan (CLS). Autophagy is a degradative process responsible for amino acid recycling in response to nitrogen starvation and amino acid limitation. We have investigated the role of autophagy during chronological aging of yeast grown in glucose minimal media containing different supplemental essential and nonessential amino acids. Deletion of ATG1 or ATG7, both of which are required for autophagy, reduced CLS, whereas deletion of ATG11, which is required for selective targeting of cellular components to the vacuole for degradation, did not reduce CLS. The nonessential amino acids isoleucine and valine, and the essential amino acid leucine, extended CLS in autophagy-deficient as well as autophagy-competent yeast. This extension was suppressed by constitutive expression of GCN4, which encodes a transcriptional regulator of general amino acid control (GAAC). Consistent with this, GCN4 expression was reduced by isoleucine and valine. Furthermore, elimination of the leucine requirement extended CLS and prevented the effects of constitutive expression of GCN4. Interestingly, deletion of LEU3, a GAAC target gene encoding a transcriptional regulator of branched side chain amino acid synthesis, dramatically increased CLS in the absence of amino acid supplements. In general, this indicates that activation of GAAC reduces CLS whereas suppression of GAAC extends CLS in minimal medium. These findings demonstrate important roles for autophagy and amino acid homeostasis in determining CLS in yeast. [source]


Stability of 5-aminolevulinic acid in novel non-aqueous gel and patch-type systems intended for topical application

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2005
Paul A. McCarron
Abstract Aminolevulinic acid (ALA) stability within topical formulations intended for photodynamic therapy (PDT) is poor due to dimerisation to pyrazine-2,5-dipropionic acid (PY). Most strategies to improve stability use low pH vehicles, which can cause cutaneous irritancy. To overcome this problem, a novel approach is investigated that uses a non-aqueous vehicle to retard proton-induced charge separation across the 4-carbonyl group on ALA and lessen nucleophilic attack that leads to condensation dimerisation. Bioadhesive anhydrous vehicles based on methylvinylether-maleic anhydride copolymer patches and poly(ethyleneglycol) or glycerol thickened poly(acrylic acid) gels were formulated. ALA stability fell below pharmaceutically acceptable levels after 6 months, with bioadhesive patches stored at 5°C demonstrating the best stability by maintaining 86.2% of their original loading. Glycerol-based gels maintained 40.2% in similar conditions. However, ALA loss did not correspond to expected increases in PY, indicating the presence of another degradative process that prevented dimerisation. Nuclear magnetic resonance (NMR) analysis was inconclusive in respect of the mechanism observed in the patch system, but showed clearly that an esterification reaction involving ALA and both glycerol and poly(ethyleneglycol) was occurring. This was especially marked in the glycerol gels, where only 2.21% of the total expected PY was detected after 204 days at 5°C. Non-specific esterase hydrolysis demonstrated that ALA was recoverable from the gel systems, further supporting esterified binding within the gel matrices. It is conceivable that skin esterases could duplicate this finding upon topical application of the gel and convert these derivatives back to ALA in situ, provided skin penetration is not affected adversely. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:1756,1771, 2005 [source]


The transient nature of maximum maleic anhydride grafting of polypropylene: A mechanistic approach based on a consecutive reaction model.

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007

Abstract This article compares the batch solution and molten state chemical modification of an atactic polypropylene to yield a grafted polypropylene. Short reaction times appear to be sufficient and indeed necessary for the highest graft yields to be obtained if degradative processes occurring in both reaction media are to be avoided. The consecutive reactions for the optimized grafting reaction pathway were proposed for the solution process in an earlier article. The present work attempts to correlate this pathway with that of the molten state process. Grafted succinic anhydride groups react with two resorcine molecules to yield grafted succinyl-fluorescein groups. This work considers the resorcine units as true molecular probes, to be able to stabilize and activate the complexes formed between the succinic anhydride groups and the propylene sequence. This work shows the unsteady and later dynamic character of the process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 345,351, 2007 [source]


Benzoic acid-degrading bacteria from the intestinal tract of Macrotermes michaelseni Sjöstedt

JOURNAL OF BASIC MICROBIOLOGY, Issue 1 2007
David Kamanda Ngugi
Abstract The intestinal tracts of termites host a wide variety of microbial symbionts, which have been implicated in degradative processes. In this study, a fungus-cultivating termite, Macrotermes michaelseni was found to harbor 2.2 × 106 bacterial cells per ml of gut homogenates capable of degrading benzoic acid. Two benzoic acid degrading bacteria were isolated from the highest dilution of gut homogenates in oxic media with benzoic acid as the sole carbon source. Isolate CBC was related to Stenotrophomonas maltophila LMG 958T, Xanthomonas campestris DSM 3586T and Stenotrophomonas acidaminophila DSM 13117T with a sequence similarity of 98.3%, 94.7% and 94.2%, respectively. Isolate CBW was related to Enterobacter aerogenes JCM 1235T and Raoultella ornithinolytica ATCC 31898T with sequence similarity of 98.4% and 97.8%, respectively. In addition to growing on benzoic acid (up to 9 mM) aerobically, isolate CBW also degraded benzoic acid under anoxic conditions with nitrate as electron acceptor. Isolate CBC did not degrade bezoic acid with nitrate but could degraded resorcinol under oxic conditions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Cryoprotective additives and cryostabilisation effects on muscle fillets of the freshwater teleost fish Rohu carp (Labeo rohita) during prolonged frozen storage

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2006
Shashi Kiran Jasra
Abstract The effects of various cryoprotective additives separately and in combination were studied on the myofibrillar protein integrity, biochemical enzyme activity levels and muscle ultrastructure in the freshwater teleost fish Rohu carp (Labeo rohita). Fish muscle samples were divided into eight groups and immersed in different mixtures of cryoprotective additives (S1,S8), then frozen at , 20 or , 30 °C for 24 months. Electrophoretic studies revealed early (within 6 months) alteration of the myofibrillar proteins myosin light chain, ,-actinin and tropomyosin. Reduction of the storage temperature from , 20 to , 30 °C slowed down the degradative processes. Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that fish muscle treated with cryoprotective mixture S8 (40 g L,1 sorbitol/3 g L,1 sodium tripolyphosphate/4 g L,1 sodium alginate) showed minimal post mortem changes in myofibrillar proteins. Ultrastructural results also revealed post mortem damage to the muscle, seen earliest (within 6 months) in the sample frozen-stored without additives (S2), as compared with the normal, unfrozen muscle (S1). The influence of cryoprotectants alone and in combination on fish muscle structural proteins, myosin and actin filaments (A and I bands), during prolonged frozen storage was investigated. After 12 months, samples frozen-stored with various cryoprotective additives (S2-S7), except S8, showed signs of myofibrillar disintegration. Beyond that time the degradative processes started showing up in all samples, with minimal muscle ultrastructural damage in sample S8. Again, reducing the storage temperature from , 20 to , 30 °C slowed down the degradative processes. Ultrastructural results correlated well with levels of biochemical enzymes (Ca2+ myofibrillar ATPase and succinic dehydrogenase) during frozen storage. This is the first report of the cryoprotective effects of these additives on this popular edible fish species. Of the various combinations of additives tested, cryoprotective mixture S8 was found to preserve the muscle structure longest under frozen storage conditions. However, even this mixture was only effective for 18 months at , 30 °C. Beyond that time the myofibrillar degradative processes were apparent with correlative electrophoretic, biochemical and ultrastructural studies. Copyright © 2006 Society of Chemical Industry [source]


Soil carbon sequestration in China through agricultural intensification, and restoration of degraded and desertified ecosystems,

LAND DEGRADATION AND DEVELOPMENT, Issue 6 2002
R. Lal
Abstract The industrial emission of carbon (C) in China in 2000 was about 1,Pg,yr,1, which may surpass that of the United States (1,84,Pg,C) by 2020. China's large land area, similar in size to that of the United States, comprises 124,Mha of cropland, 400,Mha of grazing land and 134,Mha of forestland. Terrestrial C pool of China comprises about 35,60,Pg in the forest and 120,186,Pg in soils. Soil degradation is a major issue affecting 145,Mha by different degradative processes, of which 126,Mha are prone to accelerated soil erosion. Total annual loss by erosion is estimated at 5,5,Pg of soil and 15,9,Tg of soil organic carbon (SOC). Erosion-induced emission of C into the atmosphere may be 32,64,Tg,yr,1. The SOC pool progressively declined from the 1930s to 1980s in soils of northern China and slightly increased in those of southern China because of change in land use. Management practices that lead to depletion of the SOC stock are cultivation of upland soils, negative nutrient balance in cropland, residue removal, and soil degradation by accelerated soil erosion and salinization and the like. Agricultural practices that enhance the SOC stock include conversion of upland to rice paddies, integrated nutrient management based on liberal use of biosolids and compost, crop rotations that return large quantities of biomass, and conservation-effective systems. Adoption of recommended management practices can increase SOC concentration in puddled soil, red soil, loess soils, and salt-affected soils. In addition, soil restoration has a potential to sequester SOC. Total potential of soil C sequestration in China is 105,198,Tg,C,yr,1 of SOC and 7,138,Tg,C,yr,1 for soil inorganic carbon (SIC). The accumulative potential of soil C sequestration of 11,Pg at an average rate of 224,Tg,yr,1 may be realized by 2050. Soil C sequestration potential can offset about 20 per cent of the annual industrial emissions in China. Copyright © 2002 John Wiley & Sons, Ltd. [source]